Evidence-grounded comparison · non-production preview

Compare supplement evidence clearly.

Review two canonical supplement records topic by topic, with evidence availability, source boundaries, and limitations kept explicit—without rankings or recommendations.

What this comparison can establish

This comparison organizes two separately sourced supplement records. It describes evidence structure and availability without ranking supplements or recommending use.

Reference counts are descriptive. More references do not necessarily mean better or stronger evidence.

Identity boundaries

Selected supplement concepts

Supplement concepts, ingredients, and forms remain separate. Relationship differences do not establish clinical meaning.

vitamin

Vitamin B12

Also known as Cobalamin, B12

ODS source attached

Canonical ID: entity:supplement:vitamin-b12
Identity layer: Supplement concept
Evidence status: source backed demonstration not medically reviewed
Medical review: not medically reviewed

Modeled ingredients

No ingredient relationship is modeled in this pilot.

Modeled forms

No form relationship is modeled in this pilot.

vitamin

Vitamin D

Also known as Calciferol

ODS source attached

Canonical ID: entity:supplement:vitamin-d
Identity layer: Supplement concept
Evidence status: source backed demonstration not medically reviewed
Medical review: not medically reviewed

Modeled ingredients

Ergocalciferolingredient
Cholecalciferolingredient

Modeled forms

Vitamin D2vitamin form
Vitamin D3vitamin form

Source boundaries

Selected ODS revisions

Each supplement retains its own immutable source revision, fingerprint, official URL, and medical-review state.

Selected NIH ODS revision

Vitamin B12

Vitamin B12 — Fact Sheet for Health Professionals

Source ID: source:nih-ods:vitamin-b12-health-professional
Source revision ID: source-revision:nih-ods:vitamin-b12-health-professional:2026-08-10.a488ce5e4f73
ODS revision date: July 2, 2025
Medical review: not medically reviewed
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Retrieved: 2026-08-10T22:07:05.257Z

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Selected NIH ODS revision

Vitamin D

Vitamin D — Fact Sheet for Health Professionals

Source ID: source:nih-ods:vitamin-d-health-professional
Source revision ID: source-revision:nih-ods:vitamin-d-health-professional:2026-08-10.825b1a553a4a
ODS revision date: June 27, 2025
Medical review: not medically reviewed
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Retrieved: 2026-08-10T22:07:04.753Z

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Structural orientation

What differs in these records

These statements describe record structure only and do not assign medical importance.

26 structural observations are available. Topic states remain visible in the aligned comparison below.

Inspect all structural observations

The selected ODS revision dates differ: July 2, 2025 for Vitamin B12 and June 27, 2025 for Vitamin D.
Vitamin B12 and Vitamin D have different modeled ingredient relationships. This is an identity distinction, not a clinical ranking.
Vitamin B12 and Vitamin D have different modeled form relationships. No clinical interpretation is assigned to that difference.
The selected source blocks for “What it is” link 5 references for Vitamin B12 and 4 references for Vitamin D.
The evidence profiles identify different reference types for “What it is”.
Source-backed evidence for “Common reasons people use it” is unavailable for both selected supplements.
Source-backed evidence for “What evidence has studied” is unavailable for both selected supplements.
Source-backed evidence for “Potential benefits studied” is unavailable for both selected supplements.
The selected source blocks for “Known risks and safety considerations” link 1 reference for Vitamin B12 and 10 references for Vitamin D.
The evidence profiles identify different reference types for “Known risks and safety considerations”.
Source-backed evidence for “Side effects” is unavailable for both selected supplements.
The selected source blocks for “Medication interaction evidence” link 3 references for Vitamin B12 and 13 references for Vitamin D.
The evidence profiles identify different reference types for “Medication interaction evidence”.
Source-backed evidence for “Supplement interaction evidence” is unavailable for both selected supplements.
Source-backed evidence for “Food and nutrient interactions” is unavailable for both selected supplements.
The selected source blocks for “Typical forms” link 7 references for Vitamin B12 and 10 references for Vitamin D.
The evidence profiles identify different reference types for “Typical forms”.
The selected source blocks for “Evidence-backed dosage information” link 1 reference for Vitamin B12 and 6 references for Vitamin D.
The evidence profiles identify different reference types for “Evidence-backed dosage information”.
The selected source blocks for “Populations needing caution” link 21 references for Vitamin B12 and 16 references for Vitamin D.
The evidence profiles identify different reference types for “Populations needing caution”.
Source-backed evidence for “Pregnancy and lactation considerations” is unavailable for both selected supplements.
The selected source blocks for “Laboratory and test considerations” link 7 references for Vitamin B12 and 13 references for Vitamin D.
The evidence profiles identify different reference types for “Laboratory and test considerations”.
Source-backed evidence for “Regulatory information” is unavailable for both selected supplements.
Source-backed evidence for “Evidence limitations” is unavailable for both selected supplements.

Topic-by-topic evidence

Compare evidence availability and provenance

Each source block, reference, evidence profile, and inspector remains attached to its own supplement and ODS revision.

Evidence topic

What it is

Available for both

Vitamin B12

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 5 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic reviews or meta-analyses not identified in the frozen metadata
Evidence recency: 1998–2020
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Study type could not be determined4

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
Government reference · Population basis: unknown · Directness: not assessed
Carmel R. Cobalamin (vitamin B12). In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:369-89.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Allen LH. Vitamin B12. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:812-20.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Allen LH. Vitamin B-12. Adv Nutr 2012;3:54-5. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Stabler SP. Vitamin B12. In: Marriott BP, Birt DF, Stallings VA, Yates AA, eds. Present Knowledge in Nutrition. 11th ed. Washington, DC: Elsevier; 2020:257-71.
Study type could not be determined · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin B12

Vitamin B12 is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement and a prescription medication. Because vitamin B12 contains the mineral cobalt, compounds with vitamin B12 activity are collectively called cobalamins [1]. Methylcobalamin and 5-deoxyadenosylcobalamin are the metabolically active forms of vitamin B12. However, two others forms, hydroxycobalamin and cyanocobalamin, become biologically active after they are converted to methylcobalamin or 5-deoxyadenosylcobalamin [1-3].

Vitamin B12 is required for the development, myelination, and function of the central nervous system; healthy red blood cell formation; and DNA synthesis [1,4,5]. Vitamin B12 functions as a cofactor for two enzymes, methionine synthase and L-methylmalonyl-CoA mutase [1-3,5]. Methionine synthase catalyzes the conversion of homocysteine to the essential amino acid methionine [1,2]. Methionine is required for the formation of S-adenosylmethionine, a universal methyl donor for almost 100 different substrates, including DNA, RNA, proteins, and lipids [3,5]. L-methylmalonyl-CoA mutase converts L-methylmalonyl-CoA to succinyl-CoA in the metabolism of propionate, a short-chain fatty acid [2].

Vitamin B12 is bound to protein in food and must be released before it is absorbed [5]. The process starts in the mouth when food is mixed with saliva. The freed vitamin B12 then binds with haptocorrin, a cobalamin-binding protein in the saliva. More vitamin B12 is released from its food matrix by the activity of hydrochloric acid and gastric protease in the stomach, where it then binds to haptocorrin [1]. In the duodenum, digestive enzymes free the vitamin B12 from haptocorrin, and this freed vitamin B12 combines with intrinsic factor, a transport and delivery binding protein secreted by the stomach’s parietal cells. The resulting complex is absorbed in the distal ileum by receptor-mediated endocytosis [1,5]. If vitamin B12 is added to fortified foods and dietary supplements, it is already in free form and therefore does not require the separation step.

Where did MEDucated get this?

Vitamin B12 — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Introduction
ODS revision: July 2, 2025
Retrieved: 2026-08-10T22:07:05.257Z
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Cited reference numbers: 1, 2, 3, 4, 5

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Vitamin D

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 4 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 2010–2018
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Study type could not be determined2
Systematic review1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
Government reference · Population basis: unknown · Directness: not assessed
Norman AW, Henry HH. Vitamin D. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition, 10th ed. Washington DC: Wiley-Blackwell, 2012.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Jones G. Vitamin D. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease, 11th ed. Philadelphia: Lippincott Williams & Wilkins, 2014.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Silva MC, Furlanetto TW. Intestinal absorption of vitamin D: A systematic review. Nutr Rev 2018;76:60-76. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin D

Vitamin D (also referred to as calciferol) is a fat-soluble vitamin that is naturally present in a few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet (UV) rays from sunlight strike the skin and trigger vitamin D synthesis.

Vitamin D obtained from sun exposure, foods, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first hydroxylation, which occurs in the liver, converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second hydroxylation occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol [1].

Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal bone mineralization and to prevent hypocalcemic tetany (involuntary contraction of muscles, leading to cramps and spasms). It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts [1-3]. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.

Vitamin D has other roles in the body, including reduction of inflammation as well as modulation of such processes as cell growth, neuromuscular and immune function, and glucose metabolism [1-3]. Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D. Many tissues have vitamin D receptors, and some convert 25(OH)D to 1,25(OH)2D.

In foods and dietary supplements, vitamin D has two main forms, D2 (ergocalciferol) and D3 (cholecalciferol), that differ chemically only in their side-chain structures. Both forms are well absorbed in the small intestine. Absorption occurs by simple passive diffusion and by a mechanism that involves intestinal membrane carrier proteins [4]. The concurrent presence of fat in the gut enhances vitamin D absorption, but some vitamin D is absorbed even without dietary fat. Neither aging nor obesity alters vitamin D absorption from the gut [4].

Where did MEDucated get this?

Vitamin D — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Introduction
ODS revision: June 27, 2025
Retrieved: 2026-08-10T22:07:04.753Z
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Cited reference numbers: 1, 2, 3, 4

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Evidence topic

Common reasons people use it

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

What evidence has studied

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

Potential benefits studied

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

Known risks and safety considerations

Available for both

Vitamin B12

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 1 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic reviews or meta-analyses not identified in the frozen metadata
Evidence recency: 1998–1998
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
Government reference · Population basis: unknown · Directness: not assessed

Source safety wording remains visible

Vitamin B12 does not have a tolerable upper intake level because it is generally considered to be safe, even at high doses.

UL reference intake

The FNB did not establish a UL for vitamin B12 because of its low potential for toxicity [1]. Even at large doses, vitamin B12 is generally considered to be safe because the body does not store excess amounts.

UL reference intake

Where did MEDucated get this?

Vitamin B12 — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Health Risks from Excessive Vitamin B12
ODS revision: July 2, 2025
Retrieved: 2026-08-10T22:07:05.257Z
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Cited reference numbers: 1

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Vitamin D

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 10 identified
Human evidence: Human evidence identified
Randomized trials: Randomized trial identified
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 2006–2019
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Study type could not be determined5
Case report2
Randomized controlled trial1
Meta-analysis1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
Government reference · Population basis: unknown · Directness: not assessed
Galior K, Grebe S, Singh R. Development of vitamin D toxicity from overcorrection of vitamin D deficiency: A review of case reports. Nutrients 2018, 10, 953. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Auguste BL, Avila-Casado C, Bargman JM. Use of vitamin D drops leading to kidney failure in a 54-year-old man. CMAJ 2019;191:E390-4. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Vogiatzi MG, Jacobson-Dickman E, DeBoer MD. Vitamin D supplementation and risk of toxicity in pediatrics: A review of current literature. J Clin Endocrinol Metab 2014;99:1132-41. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Singh P, Trivedi N. Tanning beds and hypervitaminosis D: A case report. Ann Intern Med 2014;160:810-1. [PubMed abstract]
Case report · Population basis: unknown · Directness: not assessed
Laurent MR, Gielen E, Pauwels S, Vanderschueren D, Bouillon R. Hypervitaminosis D associated with tanning bed use: A case report. Ann Intern Med 2017;166:155-6. [PubMed abstract]
Case report · Population basis: unknown · Directness: not assessed
Perez-Castrillon JL, Vega G, Abad L, Sanz A, Chaves J, Hernandez G, Duenas A. Effects of atorvastatin on vitamin D levels in patients with acute ischemic heart disease. Am J Cardiol 2007;99:903-5. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Jackson RD, LaCroix AZ, Gass M, Wallace RB, Robbins J, Lewis CE, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med 2006;354:669-82. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Malihi Z, Lawes CMM, Wu Z, Huang Y, Waayer D, Toop L, et al. Monthly high-dose vitamin D supplementation does not increase kidney stone risk or serum calcium: Results from a randomized controlled trial. Am J Clin Nutr 2019;109:1578-87. [PubMed abstract]
Randomized controlled trial · Population basis: unknown · Directness: not assessed
Malihi Z, Wu Z, Stewart AW, Lawes CMM, Scragg R. Hypercalcemia, hypercalciuria, and kidney stones in long-term studies of vitamin D supplementation: A systematic review and meta-analysis. Am J Clin Nutr 2016;104:1039-51. [PubMed abstract]
Meta-analysis · Population basis: unknown · Directness: not assessed

Source safety wording remains visible

Vitamin D toxicity can cause hypercalcemia, hypercalciuria, and high serum 25(OH)D concentrations; in extreme cases, it may lead to renal failure, calcification of soft tissues, cardiac arrhythmias, and death. Vitamin D toxicity is almost always a result of excessive intakes of vitamin D through supplements. Taking calcium supplements in combination with vitamin D supplements may increase the risk of certain adverse effects. The Tolerable Upper Intake Level for vitamin D ranges from 25 to 100 mcg (1,000–4,000 IU), depending on age.

UL reference intakeSource intake rangeSource-described amount

Excess amounts of vitamin D are toxic. Because vitamin D increases calcium absorption in the gastrointestinal tract, vitamin D toxicity results in marked hypercalcemia (total calcium greater than 11.1 mg/dL, beyond the normal range of 8.4–10.2 mg/dL), hypercalciuria, and high serum 25(OH)D levels (typically >375 nmol/l [150 ng/mL]) [158]. Hypercalcemia, in turn, can lead to nausea, vomiting, muscle weakness, neuropsychiatric disturbances, pain, loss of appetite, dehydration, polyuria, excessive thirst, and kidney stones.

Source intake rangeSource-described amount

In extreme cases, vitamin D toxicity causes renal failure, calcification of soft tissues throughout the body (including in coronary vessels and heart valves), cardiac arrhythmias, and even death. Vitamin D toxicity has been caused by consumption of dietary supplements that contained excessive vitamin D amounts because of manufacturing errors, that were taken inappropriately or in excessive amounts, or that were incorrectly prescribed by physicians, [158-160].

Experts do not believe that excessive sun exposure results in vitamin D toxicity because thermal activation of previtamin D3 in the skin gives rise to various non-vitamin D forms that limit formation of vitamin D3. Some vitamin D3 is also converted to nonactive forms [1]. However, frequent use of tanning beds, which provide artificial UV radiation, can lead to 25(OH)D levels well above 375 to 500 nmol/L (150–200 ng/mL) [161-163].

The combination of high intakes of calcium (about 2,100 mg/day from food and supplements) with moderate amounts of vitamin D (about 19 mcg [765 IU]/day from food and supplements) increased the risk of kidney stones by 17% over 7 years among 36,282 postmenopausal women who were randomly assigned to take 1,000 mg/day calcium and 10 mcg (400 IU)/day vitamin D or a placebo [164]. However, other, shorter (from 24 weeks to 5 years) clinical trials of vitamin D supplementation alone or with calcium in adults found greater risks of hypercalcemia and hypercalciuria, but not of kidney stones [165,166].

Source-described amount

The FNB established ULs for vitamin D in 2010 (Table 4) [1]. While acknowledging that signs and symptoms of toxicity are unlikely at daily intakes below 250 mcg (10,000 IU), the FNB noted that even vitamin D intakes lower than the ULs might have adverse health effects over time. The FNB recommended avoiding serum 25(OH)D levels above approximately 125 to 150 nmol/L (50–60 ng/mL), and it found that even lower serum levels (approximately 75–120 nmol/L [30–48 ng/mL]) are associated with increases in rates of all-cause mortality, risk of cancer at some sites (e.g., pancreas), risk of cardiovascular events, and number of falls and fractures among older adults.

Source-described amount

Table 4: Tolerable Upper Intake Levels (ULs) for Vitamin D in Micrograms (mcg) and International Units (IU) [1]
Age	Male	Female	Pregnancy	Lactation
0–6 months	25 mcg (1,000 IU)	25 mcg (1,000 IU)
7–12 months	38 mcg (1,500 IU)	38 mcg (1,500 IU)
1–3 years	63 mcg (2,500 IU)	63 mcg (2,500 IU)
4–8 years	75 mcg (3,000 IU)	75 mcg (3,000 IU)
9–13 years	100 mcg (4,000 IU)	100 mcg (4,000 IU)
14–18 years	100 mcg (4,000 IU)	100 mcg (4,000 IU)	100 mcg (4,000 IU)	100 mcg (4,000 IU)
19–50 years	100 mcg (4,000 IU)	100 mcg (4,000 IU)	100 mcg (4,000 IU)	100 mcg (4,000 IU)
51–70 years	100 mcg (4,000 IU)	100 mcg (4,000 IU)
>70 years	100 mcg (4,000 IU)	100 mcg (4,000 IU)

UL reference intakeSource-described amount

Where did MEDucated get this?

Vitamin D — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Health Risks from Excessive Vitamin D
ODS revision: June 27, 2025
Retrieved: 2026-08-10T22:07:04.753Z
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Cited reference numbers: 158, 159, 160, 1, 161, 162, 163, 164, 165, 166

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Evidence topic

Side effects

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

Medication interaction evidence

Available for both

Vitamin B12

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 3 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 2013–2018
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Meta-analysis1
Study type could not be determined2

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Jung SB, Nagaraja V, Kapur A, Eslick GD. Association between vitamin B12 deficiency and long-term use of acid-lowering agents: A systematic review and meta-analysis. Intern Med J 2015;45:409-16. [PubMed abstract]
Meta-analysis · Population basis: unknown · Directness: not assessed
Lam JR, Schneider JL, Zhao W, Corley DA. Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency. JAMA 2013;310:2435-42. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Miller JW. Proton pump inhibitors, H2-receptor antagonists, metformin, and vitamin B-12 deficiency: Clinical implications. Adv Nutr 2018;9:511S-8S. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Source safety wording remains visible

Vitamin B12 supplements may interact with medications, and some medications, including gastric acid inhibitors and metformin, may affect vitamin B12 levels.

Vitamin B12 supplements have the potential to interact with certain medications. In addition, several types of medications might adversely affect vitamin B12 levels. A few examples are provided below. Individuals taking these and other medications on a regular basis should discuss their vitamin B12 status with their health care providers.

Gastric acid inhibitors include proton pump inhibitors, such as omeprazole (Prilosec) and lansoprazole (Prevacid), and histamine 2-receptor antagonists, such as cimetidine (Tagamet) and ranitidine (Zantac). These drugs are used to treat gastroesophageal reflux disease and peptic ulcer disease. They can interfere with vitamin B12 absorption from food by slowing the release of gastric acid into the stomach and thereby lead to vitamin B12 deficiency [101-103].

Metformin, an antihyperglycemic agent used as first-line treatment for prediabetes and diabetes, might reduce the absorption of vitamin B12 and significantly reduce serum vitamin B12 concentrations [103].

Where did MEDucated get this?

Vitamin B12 — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Interactions with Medications
ODS revision: July 2, 2025
Retrieved: 2026-08-10T22:07:05.257Z
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Cited reference numbers: 101, 102, 103

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Vitamin D

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 13 identified
Human evidence: Human evidence identified
Randomized trials: Randomized trial identified
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 1984–2013
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Study type could not be determined10
Systematic review1
Randomized controlled trial2

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Gotfredsen A, Westergren Hendel H, Andersen T. Influence of orlistat on bone turnover and body composition. Int J Obes Relat Metab Disord 2001;25:1154-60. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
James WP, Avenell A, Broom J, Whitehead J. A one-year trial to assess the value of orlistat in the management of obesity. Int J Obes Relat Metab Disord 1997;21:S24-30. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
McDuffie JR, Calis KA, Booth SL, Uwaifo GI, Yanovski JA. Effects of orlistat on fat-soluble vitamins in obese adolescents. Pharmacotherapy 2002;22:814-22. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Robien K, Oppeneer SJ, Kelly JA, Hamilton-Reeves JM. Drug-vitamin D interactions: A systematic review of the literature. Nutr Clin Pract 2013;28:194-208. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed
Schwartz JB. Effects of vitamin D supplementation in atorvastatin-treated patients: A new drug interaction with an unexpected consequence. Clin Pharmacol Ther 2009;85:198-203. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Perez-Castrillon JL, Vega G, Abad L, Sanz A, Chaves J, Hernandez G, Duenas A. Effects of atorvastatin on vitamin D levels in patients with acute ischemic heart disease. Am J Cardiol 2007;99:903-5. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Aloia JF, Li-Ng M, Pollack S. Statins and vitamin D. Am J Cardiol 2007;100:1329. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Buckley LM, Leib ES, Cartularo KS, Vacek PM, Cooper SM. Calcium and vitamin D3 supplementation prevents bone loss in the spine secondary to low-dose corticosteroids in patients with rheumatoid arthritis. A randomized, double-blind, placebo-controlled trial. Ann Intern Med 1996;125:961-8. [PubMed abstract]
Randomized controlled trial · Population basis: human · Directness: not assessed
de Sevaux RGL, Hoitsma AJ, Corstens FHM, Wetzels JFM. Treatment with vitamin D and calcium reduces bone loss after renal transplantation: a randomized study. J Am Soc Nephrol 2002;13:1608-14. [PubMed abstract]
Randomized controlled trial · Population basis: unknown · Directness: not assessed
Lukert BP, Raisz LG. Glucocorticoid-induced osteoporosis: pathogenesis and management. Ann Intern Med 1990;112:352-64. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Skversky AL, Kumar J, Abramowitz MK, Kaskel FJ, Melamed ML. Association of glucocorticoid use and low 25-hydroxyvitamin D levels: Results from the National Health and Nutrition Examination Survey (NHANES): 2001-2006. J Clin Endocrinol Metab 2011;96:3838-45. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Drinka PJ, Nolten WE. Hazards of treating osteoporosis and hypertension concurrently with calcium, vitamin D, and distal diuretics. J Am Geriatr Soc 1984;32:405-7. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Crowe M, Wollner L, Griffiths RA. Hypercalcaemia following vitamin D and thiazide therapy in the elderly. Practitioner 1984;228:312-3. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Source safety wording remains visible

Vitamin D supplements may interact with medications, and some medications may affect vitamin D levels. These medications include orlistat, statins, steroids, and thiazide diuretics.

Vitamin D supplements may interact with several types of medications. A few examples are provided below. Individuals taking these and other medications on a regular basis should discuss their vitamin D intakes and status with their health care providers.

The weight-loss drug orlistat (Xenical and alli), together with a reduced-fat diet, can reduce the absorption of vitamin D from food and supplements, leading to lower 25(OH)D levels [167-170].

Statin medications reduce cholesterol synthesis. Because endogenous vitamin D is derived from cholesterol, statins may also reduce vitamin D synthesis [170]. In addition, high intakes of vitamin D, especially from supplements, might reduce the potency of atorvastatin (Lipitor), lovastatin (Altoprev and Mevacor), and simvastatin (FloLipid and Zocor), because these statins and vitamin D appear to compete for the same metabolizing enzyme [170-173].

Corticosteroid medications, such as prednisone (Deltasone, Rayos, and Sterapred), are often prescribed to reduce inflammation. These medications can reduce calcium absorption and impair vitamin D metabolism [174-176]. In the NHANES 2001–2006 survey, 25(OH)D deficiency (less than 25 nmol/L [10 ng/mL]) was more than twice as common among children and adults who reported oral steroid use (11%) than in nonusers (5%) [177].

Thiazide diuretics (e.g., Hygroton, Lozol, and Microzide) decrease urinary calcium excretion. The combination of these diuretics with vitamin D supplements (which increase intestinal calcium absorption) might lead to hypercalcemia, especially among older adults and individuals with compromised renal function or hyperparathyroidism [170,178,179].

Where did MEDucated get this?

Vitamin D — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Interactions with Medications
ODS revision: June 27, 2025
Retrieved: 2026-08-10T22:07:04.753Z
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Cited reference numbers: 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Evidence topic

Supplement interaction evidence

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

Food and nutrient interactions

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

Typical forms

Available for both

Vitamin B12

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 7 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trial identified
Reviews and meta-analyses: Systematic reviews or meta-analyses not identified in the frozen metadata
Evidence recency: 1998–2021
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Study type could not be determined5
Randomized controlled trial1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
Government reference · Population basis: unknown · Directness: not assessed
Allen LH. Vitamin B12. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:812-20.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Label Database. 2021.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Paul C, Brady DM. Comparative bioavailability and utilization of particular forms of B(12) Supplements with potential to mitigate B(12)-related genetic polymorphisms. Integr Med 2017;16:42-9. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood 2008;112:2214-21. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Yazaki Y, Chow G, Mattie M. A single-center, double-blinded, randomized controlled study to evaluate the relative efficacy of sublingual and oral vitamin B-complex administration in reducing total serum homocysteine levels. J Altern Complement Med 2006;12:881-5. [PubMed abstract]
Randomized controlled trial · Population basis: unknown · Directness: not assessed
Sharabi A, Cohen E, Sulkes J, Garty M. Replacement therapy for vitamin B12 deficiency: Comparison between the sublingual and oral route. Br J Clin Pharmacol 2003;56:635-8. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin B12

Vitamin B12 is present in many dietary supplements, often as cyanocobalamin, but other forms may also be used. Supplements that only contain vitamin B12 typically have the highest doses of the vitamin, while multivitamin/mineral supplements and supplements that combine vitamin B12 with other B-complex vitamins usually contain lower doses.

Vitamin B12 is available in multivitamin/mineral supplements, in supplements containing other B-complex vitamins, and in supplements containing only vitamin B12. Multivitamin/mineral supplements typically contain vitamin B12 at doses ranging from 5 to 25 mcg [23]. Vitamin B12 levels are higher, generally 50 to 500 mcg, in supplements containing vitamin B12 with other B-complex vitamins and even higher, typically 500 to 1,000 mcg, in supplements containing only vitamin B12.

Source intake rangeSource-described amount

The most common form of vitamin B12 in dietary supplements is cyanocobalamin [1,3,23,24]. Other forms of vitamin B12 in supplements are adenosylcobalamin, methylcobalamin, and hydroxycobalamin [23].

No evidence indicates that absorption rates of vitamin B12 in supplements vary by form of the vitamin. These rates are about 50% at doses (less than 1–2 mcg) that do not exceed the cobalamin-binding capacity of intrinsic factor and are substantially lower at doses well above 1 to 2 mcg [24,25]. For example, absorption is only about 2% at doses of 500 mcg and 1.3% at doses of 1,000 mcg [25].

Source intake rangeSource-described amount

In addition to oral dietary supplements, vitamin B12 is available in sublingual preparations as tablets or lozenges [23]. Evidence suggests no difference in efficacy between oral and sublingual forms [26,27].

Where did MEDucated get this?

Vitamin B12 — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Dietary supplements
ODS revision: July 2, 2025
Retrieved: 2026-08-10T22:07:05.257Z
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Cited reference numbers: 23, 1, 3, 24, 25, 26, 27

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Vitamin D

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 10 identified
Human evidence: Human evidence identified
Randomized trials: Randomized trial identified
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 2007–2020
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Systematic review1
Study type could not be determined6
Meta-analysis1
Randomized controlled trial2

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Silva MC, Furlanetto TW. Intestinal absorption of vitamin D: A systematic review. Nutr Rev 2018;76:60-76. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed
Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Hirsch AL. Industrial Aspects of Vitamin D. In: Feldman D, Pike JW, Adams JS, eds. Vitamin D. 3rd ed. Academic Press; 2011:73-93.
Study type could not be determined · Population basis: unknown · Directness: not assessed
National Institutes of Health. Dietary Supplement Label Database. 2020.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: A systematic review and meta-analysis. Am J Clin Nutr 2012;95:1357-64. [PubMed abstract]
Meta-analysis · Population basis: unknown · Directness: not assessed
Lehmann U, Hirche F, Stangl GI, Hinz K, Westphal S, Dierkes J. Bioavailability of vitamin D2 and D3 in healthy volunteers, a randomised placebo-controlled trial. J Clin Endocrin Metab 2013;98:4339-45. [PubMed abstract]
Randomized controlled trial · Population basis: human · Directness: not assessed
Logan VF, Gray AR, Peddie MC, Harper MJ, Houghton LA. Long-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months. Br J Nutr 2013;109:1082-8. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Tripkovic L, Wilson LR, Hart K, Johnsen S, de Lusignan S, Smith CP, et al. Daily supplementation with 15 µg vitamin D2 compared with vitamin D3 to increase wintertime 25-hydroxyvitamin D status in healthy South Asian and white European women: A 12-wk randomized, placebo-controlled food-fortification trial. Am J Clin Nutr 2017;106:481-90. [PubMed abstract]
Randomized controlled trial · Population basis: human · Directness: not assessed
Graeff-Armas LA, Bendik I, Kunz I, Schoop R, Hull S, Beck M. Supplemental 25-hydroxycholecalciferol is more effective than cholecalciferol in raising serum 25-hydroxyvitamin D concentrations in older adults. J Nutr 2020;150:73-81. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Quesada-Gomez JM, Bouillon R. Is calcifediol better than cholecalciferol for vitamin D supplementation? Osteoporos Int 2018;29:1697-1711. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin D

Vitamin D is present in dietary supplements as either vitamin D2 or vitamin D3. Both can raise the serum level of 25(OH)D. However, research shows that vitamin D3 increases serum 25(OH)D levels to a greater extent than vitamin D2 and can maintain those higher levels for longer periods of time.

Dietary supplements can contain vitamins D2 or D3. Vitamin D2 is manufactured using UV irradiation of ergosterol in yeast, and vitamin D3 is typically produced with irradiation of 7-dehydrocholesterol from lanolin obtained from the wool of sheep [13,31]. An animal-free version of vitamin D3 sourced from lichen is also available [32]. People who avoid all animal-sourced products can contact dietary supplement manufacturers to ask about their sourcing and processing techniques.

Both vitamins D2 and D3 raise serum 25(OH)D levels, and they seem to have equivalent ability to cure rickets [4]. In addition, most steps in the metabolism and actions of vitamins D2 and D3 are identical. However, most evidence indicates that vitamin D3 increases serum 25(OH)D levels to a greater extent and maintains these higher levels longer than vitamin D2, even though both forms are well absorbed in the gut [33-36].

Some studies have used dietary supplements containing the 25(OH)D3 form of vitamin D. Per equivalent microgram dose, 25(OH)D3 is three to five times as potent as vitamin D3 [37,38]. However, no 25(OH)D3 dietary supplements appear to be available to consumers on the U.S. market at this time [32].

Where did MEDucated get this?

Vitamin D — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Dietary supplements
ODS revision: June 27, 2025
Retrieved: 2026-08-10T22:07:04.753Z
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Cited reference numbers: 13, 31, 32, 4, 33, 34, 35, 36, 37, 38

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Evidence topic

Evidence-backed dosage information

Available for both

Vitamin B12

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 1 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic reviews or meta-analyses not identified in the frozen metadata
Evidence recency: 1998–1998
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
Government reference · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin B12

The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine has established Recommended Dietary Allowances and Adequate Intakes for vitamin B12. These values range from 2.4 to 2.8 mcg for adults and from 0.4 to 2.8 mcg for infants, children, and adolescents, depending on age.

RDA reference intakeAI reference intakeSource intake rangeSource-described amount

Intake recommendations for vitamin B12 and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine [1]. DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and sex, include the following:

Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals
Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA
Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals
Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects

RDA reference intakeAI reference intakeUL reference intake

Table 1 lists the current RDAs for vitamin B12 [1]. For adults, the main criterion that the FNB used to establish the RDAs was the amount needed to maintain a healthy hematological status and serum vitamin B12 levels. For infants age 0 to 12 months, the FNB established an AI that is equivalent to the mean intake of vitamin B12 in healthy, breastfed infants.

AI reference intake

Table 1: Recommended Dietary Allowances (RDAs) for Vitamin B12 in Micrograms (mcg)[1]
Age	Male	Female	Pregnancy	Lactation
Birth to 6 months*	0.4 mcg	0.4 mcg
7–12 months*	0.5 mcg	0.5 mcg
1–3 years	0.9 mcg	0.9 mcg
4–8 years	1.2 mcg	1.2 mcg
9–13 years	1.8 mcg	1.8 mcg
14–18 years	2.4 mcg	2.4 mcg	2.6 mcg	2.8 mcg
19+ years	2.4 mcg	2.4 mcg	2.6 mcg	2.8 mcg
* Adequate Intake (AI)

RDA reference intakeAI reference intakeSource-described amount

Where did MEDucated get this?

Vitamin B12 — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Recommended Intakes
ODS revision: July 2, 2025
Retrieved: 2026-08-10T22:07:05.257Z
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Cited reference numbers: 1

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Vitamin D

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 6 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 2010–2024
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Clinical guideline3
Systematic review1
Study type could not be determined1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
Government reference · Population basis: unknown · Directness: not assessed
Sempos CT, Binkley N. 25-hydroxyvitamin D assay standardisation and vitamin D guidelines paralysis. Public Health Nutrition 2020;23:1153-64. [PubMed abstract]
Clinical guideline · Population basis: unknown · Directness: not assessed
Demay MB, Pittas AG, Bikle DD, Diab DL, Kiely ME, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2024 Jul 12;109(8):1907-1947. [PubMed abstract]
Clinical guideline · Population basis: unknown · Directness: not assessed
Shah VP, Nayfeh T, Alsawaf Y, Saadi S, Farah M, et al. A Systematic Review Supporting the Endocrine Society Clinical Practice Guidelines on Vitamin D. J Clin Endocrinol Metab. 2024 Jul 12;109(8):1961-1974. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed
Bouillon R. Comparative analysis of nutritional guidelines for vitamin D. Nat Rev Endocrinol 2017;13:466-79. [PubMed abstract]
Clinical guideline · Population basis: unknown · Directness: not assessed
Scientific Advisory Committee on Nutrition. Vitamin D and Health. 2016.
Study type could not be determined · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin D

The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine has established Recommended Dietary Allowances and Adequate Intakes for vitamin D. These values range from 15 to 20 mcg (600–800 IU) for adults and from 10 to 15 mcg (400–600 IU) for infants, children, and adolescents, depending on age.

RDA reference intakeAI reference intakeSource intake rangeSource-described amount

Intake recommendations for vitamin D and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by expert committees of NASEM [1]. DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values include the following:

Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals
Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA
Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals
Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects

RDA reference intakeAI reference intakeUL reference intake

The FNB established RDAs for vitamin D to indicate daily intakes sufficient to maintain bone health and normal calcium metabolism in healthy people. RDAs for vitamin D are listed in both micrograms (mcg) and International Units (IU); 1 mcg vitamin D is equal to 40 IU (Table 2). Even though sunlight is a major source of vitamin D for some people, the FNB based the vitamin D RDAs on the assumption that people receive minimal sun exposure [1]. For infants from birth to 12 months, the FNB developed AIs based on the amount of vitamin D that maintains serum 25(OH)D levels above 20 ng/mL (50 nmol/L) and supports bone development.

Source-described amount

Table 2: Recommended Dietary Allowances (RDAs) for Vitamin D in Micrograms (mcg) and International Units (IU) [1]
Age	Male	Female	Pregnancy	Lactation
0–6 months*	10 mcg (400 IU)*	10 mcg (400 IU)*
7–12 months*	10 mcg (400 IU)*	10 mcg (400 IU)*
1–3 years	15 mcg (600 IU)	15 mcg (600 IU)
4–8 years	15 mcg (600 IU)	15 mcg (600 IU)
9–13 years	15 mcg (600 IU)	15 mcg (600 IU)
14–18 years	15 mcg (600 IU)	15 mcg (600 IU)	15 mcg (600 IU)	15 mcg (600 IU)
19–50 years	15 mcg (600 IU)	15 mcg (600 IU)	15 mcg (600 IU)	15 mcg (600 IU)
51–70 years	15 mcg (600 IU)	15 mcg (600 IU)
>70 years	20 mcg (800 IU)	20 mcg (800 IU)
*Adequate Intake (AI)

RDA reference intakeAI reference intakeSource-described amount

Many other countries around the world and some professional societies have somewhat different guidelines for vitamin D intakes [15]. These differences are a result of an incomplete understanding of the biology and clinical implications of vitamin D, different purposes for the guidelines (e.g., for public health in a healthy population or for clinical practice), and/or the use in some guidelines of observational studies in addition to randomized clinical trials to establish recommendations [9,15]. For example, the United Kingdom Scientific Advisory Committee on Nutrition recommends intakes of 10 mcg (400 IU)/day for individuals age 4 years and older [16]. The Endocrine Society recommends routine vitamin D supplementation for children and teens age 1 to 18 years, pregnant women, adults with pre-diabetes, and adults age 75 years and older, but not for healthy adults age 19 to 74 [11,12]. The Endocrine Society does not recommend specific doses but notes that all individuals should adhere to the RDA.

RDA reference intakeSource-described amount

Where did MEDucated get this?

Vitamin D — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Recommended Intakes
ODS revision: June 27, 2025
Retrieved: 2026-08-10T22:07:04.753Z
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Cited reference numbers: 1, 9, 11, 12, 15, 16

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Evidence topic

Populations needing caution

Available for both

Vitamin B12

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 21 identified
Human evidence: Human evidence identified
Randomized trials: Randomized trial identified
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 1998–2019
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Study type could not be determined15
Meta-analysis1
Randomized controlled trial1
Narrative review2
Systematic review1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
Government reference · Population basis: unknown · Directness: not assessed
Carmel R. Cobalamin (vitamin B12). In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:369-89.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Allen LH. Vitamin B12. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:812-20.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Allen LH, Miller JW, de Groot L, Rosenberg IH, Smith AD, Refsum H, et al. Biomarkers of Nutrition for Development (BOND): Vitamin B-12 Review. J Nutr 2018;148:1995S-2027S. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Green R, Allen LH, Bjorke-Monsen AL, Brito A, Gueant JL, Miller JW, et al. Vitamin B12 deficiency. Nat Rev Dis Primers 2017;3:17040. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Wong CW. Vitamin B12 deficiency in the elderly: Is it worth screening? Hong Kong Med J 2015;21:155-64. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Pfisterer KJ, Sharratt MT, Heckman GG, Keller HH. Vitamin B12 status in older adults living in Ontario long-term care homes: prevalence and incidence of deficiency with supplementation as a protective factor. Appl Physiol Nutr Metab 2016;41:219-22. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Cavalcoli F, Zilli A, Conte D, Massironi S. Micronutrient deficiencies in patients with chronic atrophic autoimmune gastritis: A review. World J Gastroenterol 2017;23:563-72. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Weck MN, Stegmaier C, Rothenbacher D, Brenner H. Epidemiology of chronic atrophic gastritis: Population-based study among 9444 older adults from Germany. Aliment Pharmacol Ther 2007;26:879-87. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Kalkan Ç, Karakaya F, Tüzün A, Gençtürk ZB, Soykan I. Factors related to low serum vitamin B12 levels in elderly patients with non-atrophic gastritis in contrast to patients with normal vitamin B12 levels. Geriatr Gerontol Int 2016;16:686-92. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Rojas Hernandez CM, Oo TH. Advances in mechanisms, diagnosis, and treatment of pernicious anemia. Discov Med 2015;19:159-68. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Ao M, Tsuji H, Shide K, Kosaka Y, Noda A, Inagaki N, et al. High prevalence of vitamin B-12 insufficiency in patients with Crohn's disease. Asia Pac J Clin Nutr 2017;26:1076-81. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Bledsoe AC, King KS, Larson JJ, Snyder M, Absah I, Choung RS, et al. Micronutrient deficiencies Are common in contemporary celiac disease despite lack of overt malabsorption symptoms. Mayo Clin Proc 2019;94:1253-60. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Ward MG, Kariyawasam VC, Mogan SB, Patel KV, Pantelidou M, Sobczyńska-Malefora A, et al. Prevalence and risk factors for functional vitamin B12 deficiency in patients with Crohn's disease. Inflamm Bowel Dis 2015;21:2839-47. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Pan Y, Liu Y, Guo H, Jabir MS, Liu X, Cui W, et al. Associations between folate and vitamin B12 levels and inflammatory bowel disease: A meta-analysis. Nutrients 2017;9:382. [PubMed abstract]
Meta-analysis · Population basis: unknown · Directness: not assessed
Gomollón F, Gargallo CJ, Muñoz JF, Vicente R, Lue A, Mir A, et al. Oral cyanocobalamin is effective in the treatment of vitamin B12 deficiency in Crohn's disease. Nutrients 2017;9:308. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Dogan K, Aarts EO, Koehestanie P, Betzel B, Ploeger N, de Boer H, et al. Optimization of vitamin suppletion after Roux-en-Y gastric bypass surgery can lower postoperative deficiencies: a randomized controlled trial. Medicine (Baltimore) 2014;93:e169. [PubMed abstract]
Randomized controlled trial · Population basis: unknown · Directness: not assessed
Kornerup LS, Hvas CL, Abild CB, Richelsen B, Nexo E. Early changes in vitamin B12 uptake and biomarker status following Roux-en-Y gastric bypass and sleeve gastrectomy. Clin Nutr 2019;38:906-11. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Pawlak R, Lester SE, Babatunde T. The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: A review of literature. Eur J Clin Nutr 2014;68:541-8. [PubMed abstract]
Narrative review · Population basis: unknown · Directness: not assessed
Dror DK, Allen LH. Vitamin B-12 in human milk: A systematic review. Adv Nutr 2018;9:358s-66s. [PubMed abstract]
Systematic review · Population basis: human · Directness: not assessed
Piccoli GB, Clari R, Vigotti FN, Leone F, Attini R, Cabiddu G, et al. Vegan-vegetarian diets in pregnancy: Danger or panacea? A systematic narrative review. Bjog 2015;122:623-33. [PubMed abstract]
Narrative review · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin B12

Certain groups of people are more likely than others to be vitamin B12 deficient. These include older adults, people with pernicious anemia or gastrointestinal disorders, and those who have had gastrointestinal surgery. Other groups that are at risk of vitamin B12 deficiency include people who follow vegetarian diets and the infants of women who follow vegan diets.

The following groups are among those most likely to be vitamin B12 deficient.

Depending on the definition used, between 3% and 43% of community-dwelling older adults, especially those with atrophic gastritis, have vitamin B12 deficiency based on serum vitamin B12 levels [43,44]. The deficiency rate at a cutoff of less than 211 pg/mL (156 pmol/L) at admission to a long-term care facility, according to one study, was 14%, and 38% of these older adults had levels lower than 407 pg/mL (300 pmol/L) [44].

Conditions associated with vitamin B12 inadequacy include pernicious anemia, present in about 15% to 25% of older adults with vitamin B12 deficiency [45]. Atrophic gastritis, an autoimmune condition affecting 2% of the general population but 8% to 9% of adults age 65 and older, decreases production of intrinsic factor and secretion of hydrochloric acid in the stomach and thus decreases absorption of vitamin B12 [45,46]. A third condition associated with vitamin B12 deficiency in older adults is Helicobacter pylori infection, possibly because this bacterium causes inflammation that leads to malabsorption of vitamin B12 from food [47].

Pernicious anemia is an irreversible autoimmune disease that affects the gastric mucosa and results in gastric atrophy [1,48]. This disease leads to attacks on parietal cells in the stomach, resulting in failure to produce intrinsic factor and malabsorption of dietary vitamin B12, recycled biliary vitamin B12, and free vitamin B12 [1,6,11].Therefore, without treatment, pernicious anemia causes vitamin B12 deficiency, even in the presence of adequate vitamin B12 intakes.

Pernicious anemia is the most common cause of clinically evident vitamin B12 deficiency around the world [11,48]. The incidence of pernicious anemia in the United States is an estimated 151 per 100,000, and this condition is more common in women and in people of European ancestry [48].

Individuals with stomach and small intestine disorders, such as celiac disease and Crohn’s disease, may be unable to absorb enough vitamin B12 from food to maintain healthy body stores [2,3,49]. However, although rates of vitamin B12 deficiency are higher in people with celiac disease than other people [50], the evidence for whether rates of vitamin B12 deficiency are higher in people with Crohn’s disease is mixed [49,51,52]. Vitamin B12 deficiency in people with Crohn’s disease is typically treated with intramuscular cobalamin injections, but high doses of oral cyanocobalamin therapy (e.g., 1,000 mcg/day) might be equally effective [53].

Source-described amount

Surgical procedures in the gastrointestinal tract, such as for weight loss or to remove all or part of the stomach, can cause a complete or partial loss of cells that secrete hydrochloric acid and cells that secrete intrinsic factor [54,55]. Thus, these procedures reduce the amount of vitamin B12, particularly food-bound vitamin B12, that the body absorbs [54,55]. High doses (1,000 mcg/day) of oral methylcobalamin supplements appear to be as effective as hydroxycobalamin injections in normalizing vitamin B12 values in patients who have undergone Roux-en-Y gastric bypass surgery [55].

Source-described amount

Vegans who consume no animal products and vegetarians who consume some animal products (e.g., dairy products, eggs, or both) but not meat have a higher risk of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods [3,57]. Consumption of foods fortified with vitamin B12 (such as fortified nutritional yeasts) as well as vitamin B12 supplements can substantially reduce the risk of deficiency [57].

Exclusively breastfed infants of women who consume no animal products might have very limited reserves of vitamin B12 and can develop vitamin B12 deficiency, sometimes very early in life [58]. The infant’s deficiency can be severe, especially if the mother’s deficiency is severe or caused by pernicious anemia; sometimes, the mother’s own deficiency is clinically mild and not recognized. Undetected and untreated vitamin B12 deficiency in infants can result in neurological damage, failure to thrive, developmental delays, and anemia [2,58,59]. The reasons include the small amounts of vitamin B12 in the breast milk of vegan mothers as well as the limited amounts of vitamin B12 crossing the placenta in these women during fetal development.

Where did MEDucated get this?

Vitamin B12 — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Groups at Risk of Vitamin B12 Inadequacy
ODS revision: July 2, 2025
Retrieved: 2026-08-10T22:07:05.257Z
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Cited reference numbers: 43, 44, 45, 46, 47, 1, 6, 11, 48, 2, 3, 49, 50, 51, 52, 53, 54, 55, 57, 58, 59

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Vitamin D

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 16 identified
Human evidence: Human evidence identified
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 2001–2020
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Systematic review2
Study type could not be determined10
Clinical guideline2
Narrative review1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
Government reference · Population basis: unknown · Directness: not assessed
Silva MC, Furlanetto TW. Intestinal absorption of vitamin D: A systematic review. Nutr Rev 2018;76:60-76. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed
Brown LL, Cohen B, Tabor D, Zappala G, Maruvada P, Coates PM. The vitamin D paradox in Black Americans: A systems-based approach to investigating clinical practice, research, and public health—expert panel meeting report. BMC Proceedings, 2018;12(Suppl 6):6. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Picciano MF. Nutrient composition of human milk. Pediatr Clin North Am 2001;48:53-67. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Wagner CL, Greer FR, American Academy of Pediatrics Section on Breastfeeding, American Academy of Pediatrics Committee on Nutrition. Prevention of rickets and vitamin D deficiency in infants, children, and adolescents. Pediatrics 2008;122:1142-52. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Dawodu A, Tsang RC. Maternal vitamin D status: Effect on milk vitamin D content and vitamin D status of breastfeeding infants. Adv Nutr 2012;3:353-61. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Davis CD, Dwyer JT. The 'sunshine vitamin': benefits beyond bone? J Natl Cancer Inst 2007;99:1563-5. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Simon AE, Ahrens KA. Adherence to vitamin D intake guidelines in the United States. Pediatrics 2020;145:e20193574. [PubMed abstract]
Clinical guideline · Population basis: unknown · Directness: not assessed
Chalcraft JR, Cardinal LM, Wechsler PJ, Hollis BW, Gerow KG, Alexander BM, et al. Vitamin D synthesis following a single bout of sun exposure in older and younger men and women. Nutrients 2020; 12, 2237; doi:10.3390/nu12082237. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Sowah D, Fan X, Dennett L, Hagtvedt R, Straube S. Vitamin D levels and deficiency with different occupations: A systematic review. BMC Public Health 2017;17:519. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed
Pappa HM, Bern E, Kamin D, Grand RJ. Vitamin D status in gastrointestinal and liver disease. Curr Opin Gastroenterol 2008;24:176-83. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Drincic A, Fuller E, Heaney RP, Armas LAG. 25-hydroxyvitamin D response to graded vitamin D3 supplementation among obese adults. J Clin Endocrinol Metab 2013;98:4845-51. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Ekwaru JP, Zwicker JD, Holick MF, Giovannucci E, Veugelers PJ. The importance of body weight for the dose response relationship of oral vitamin D supplementation and serum 25-hydroxyvitamin D in healthy volunteers. PLOS ONE 2014;9:e111265. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Chakhtoura M, Rahme M, Fuleihan E-H. Vitamin D metabolism in bariatric surgery. Endocrinol Metab Clin North Am 2017;46:947-82. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Peterson L, Zeng X, Caufield-Noll CP, Schweitzer MA, Magnuson TH, Steele KE. Vitamin D status and supplementation before and after bariatric surgery: A comprehensive literature review. Surg Obes Relat Dis 2016;12:693-702. [PubMed abstract]
Narrative review · Population basis: unknown · Directness: not assessed
Chakhtoura MT, Nakhoul N, Akl EA, Mantzoros CS, El Hajj Guleihan GA. Guidelines on vitamin D replacement in bariatric surgery? Identification and systematic appraisal. Metabolism 2016;65:586-97. [PubMed abstract]
Clinical guideline · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin D

Certain groups of people are more likely than others to have inadequate vitamin D status. These include breastfed infants, older adults, people with limited sun exposure, people with dark skin, people with conditions that limit fat absorption, and people with obesity or those who have undergone gastric bypass surgery.

Obtaining sufficient vitamin D from natural (nonfortified) food sources alone is difficult. For many people, consuming vitamin D-fortified foods and exposing themselves to some sunlight are essential for maintaining a healthy vitamin D status. However, some groups might need dietary supplements to meet their vitamin D requirements. The following groups are among those most likely to have inadequate vitamin D status.

Consumption of human milk alone does not ordinarily enable infants to meet vitamin D requirements, because it provides less than 0.6 to 2.0 mcg/L (25 to 78 IU/L) [1,56,57]. The vitamin D content of human milk is related to the mother’s vitamin D status; studies suggest that the breastmilk of mothers who take daily supplements containing at least 50 mcg (2,000 IU) vitamin D3 have higher levels of the nutrient [57,58].

Source intake rangeSource-described amount

Although UVB exposure can produce vitamin D in infants, the American Academy of Pediatrics (AAP) advises parents to keep infants younger than 6 months out of direct sunlight, dress them in protective clothing and hats, and apply sunscreen on small areas of exposed skin when sun exposure is unavoidable [59]. The AAP recommends 10 mcg (400 IU)/day vitamin D supplements for exclusively and partially breastfed infants starting shortly after birth and lasting until they are weaned and consume at least 1,000 mL/day vitamin D-fortified formula or whole milk [57]. The AAP also recommends 10 mcg (400 IU)/day supplemental vitamin D for all infants who are not breastfed and ingest less than 1,000 mL/day vitamin D-fortified formula or milk. An analysis of NHANES 2009–2016 data found that only 20.5% of breastfed infants and 31.1% of infants who were not breastfed ingested these recommended amounts of supplements [60].

Source-described amount

Older adults are at increased risk of developing vitamin D insufficiency, partly because the skin's ability to synthesize vitamin D declines with age [1,61]. In addition, older adults are likely to spend more time than younger people indoors, and they might have inadequate dietary intakes of the vitamin [1].

Homebound individuals; people who wear long robes, dresses, or head coverings for religious reasons; and people with occupations that limit sun exposure are among the groups that are unlikely to obtain adequate amounts of vitamin D from sunlight [62]. The use of sunscreen also limits vitamin D synthesis from sunlight. However, because the extent and frequency of sunscreen use are unknown, the role that sunscreen may play in reducing vitamin D synthesis is unclear [1].

Greater amounts of the pigment melanin in the epidermal layer of the skin result in darker skin and reduce the skin’s ability to produce vitamin D from sunlight [1]. Black Americans, for example, typically have lower serum 25(OH)D levels than White Americans. However, whether these lower levels in persons with dark skin have significant health consequences is not clear [14]. Those of African American ancestry, for example, have lower rates of bone fracture and osteoporosis than do Whites (see the section below on bone health and osteoporosis).

Because vitamin D is fat soluble, its absorption depends on the gut’s ability to absorb dietary fat [4]. Fat malabsorption is associated with medical conditions that include some forms of liver disease, cystic fibrosis, celiac disease, Crohn’s disease, and ulcerative colitis [1,63]. In addition to having an increased risk of vitamin D deficiency, people with these conditions might not eat certain foods, such as dairy products (many of which are fortified with vitamin D), or eat only small amounts of these foods. Individuals who have difficulty absorbing dietary fat might therefore require vitamin D supplementation [63].

Individuals with a body mass index (BMI) of 30 or more have lower serum 25(OH)D levels than individuals without obesity. Obesity does not affect the skin’s capacity to synthesize vitamin D. However, greater amounts of subcutaneous fat sequester more of the vitamin [1]. People with obesity might need greater intakes of vitamin D to achieve 25(OH)D levels similar to those of people with normal weight [1,64,65].

Individuals with obesity who have undergone gastric bypass surgery can also become vitamin D deficient. In this procedure, part of the upper small intestine, where vitamin D is absorbed, is bypassed, and vitamin D that is mobilized into the bloodstream from fat stores might not raise 25(OH)D to adequate levels over time [66,67]. Various expert groups—including the American Association of Metabolic and Bariatric Surgery, The Obesity Society, and the British Obesity and Metabolic Surgery Society—have developed guidelines on vitamin D screening, monitoring, and replacement before and after bariatric surgery [66,68]

Where did MEDucated get this?

Vitamin D — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Groups at Risk of Vitamin D Inadequacy
ODS revision: June 27, 2025
Retrieved: 2026-08-10T22:07:04.753Z
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Cited reference numbers: 1, 56, 57, 58, 59, 60, 61, 62, 14, 4, 63, 64, 65, 66, 67, 68

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Evidence topic

Pregnancy and lactation considerations

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

Laboratory and test considerations

Available for both

Vitamin B12

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 7 identified
Human evidence: Human evidence not identified in the frozen metadata
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic reviews or meta-analyses not identified in the frozen metadata
Evidence recency: 2014–2020
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Study type could not be determined7

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Carmel R. Cobalamin (vitamin B12). In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:369-89.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Allen LH, Miller JW, de Groot L, Rosenberg IH, Smith AD, Refsum H, et al. Biomarkers of Nutrition for Development (BOND): Vitamin B-12 Review. J Nutr 2018;148:1995S-2027S. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Langan RC, Goodbred AJ. Vitamin B12 deficiency: Recognition and management. Am Fam Physician 2017;96:384-9. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Maruvada P, Stover PJ, Mason JB, Bailey RL, Davis CD, Field MS, et al. Knowledge gaps in understanding the metabolic and clinical effects of excess folates/folic acid: A summary, and perspectives, from an NIH workshop. Am J Clin Nutr 2020;112:1390-403 [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Hannibal L, Lysne V, Bjørke-Monsen A-L, Behringer S, Grünert SC, Spiekerkoetter U, et al. Biomarkers and algorithms for the diagnosis of vitamin B12 deficiency. Front Mol Biosci 2016;3:27. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Mineva EM, Sternberg MR, Zhang M, Aoki Y, Storandt R, Bailey RL, et al. Age-specific reference ranges are needed to interpret serum methylmalonic acid concentrations in the US population. Am J Clin Nutr 2019;110:158-68. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Green R, Allen LH, Bjorke-Monsen AL, Brito A, Gueant JL, Miller JW, et al. Vitamin B12 deficiency. Nat Rev Dis Primers 2017;3:17040. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin B12

Serum or plasma vitamin B12 levels are typically used to assess a person’s vitamin B12 status, with values lower than 200 or 250 pg/mL generally being considered subnormal. The most sensitive marker of vitamin B12 status is a vitamin B12-associated metabolite called methylmalonic acid, and serum levels of this metabolite can be used to confirm a diagnosis of vitamin B12 deficiency if a patient’s serum vitamin B12 level is between 150 and 399 pg/mL.

Vitamin B12 status is typically assessed by measurements of serum or plasma vitamin B12 levels. The cutoff between normal vitamin B12 levels and deficiency varies by method and laboratory, but most laboratories define subnormal serum or plasma values as those lower than 200 or 250 picograms per milliliter (pg/mL) (148 or 185 picomols per liter [pmol/L]) [2]. Levels of serum methylmalonic acid (MMA), a vitamin B12-associated metabolite, are the most sensitive markers of vitamin B12 status, and an MMA level greater than 0.271 micromol/L suggests vitamin B12 deficiency [6-8]. However, MMA levels also rise with renal insufficiency and tend to be higher in older adults [6,9,10]. Another marker is total plasma homocysteine levels, which rise quickly as vitamin B12 status declines; a serum homocysteine level higher than 15 micromol/L, for example, suggests vitamin B12 deficiency [11]. However, this indicator has poor specificity because it is influenced by other factors, such as low folate levels and, especially, by declines in kidney function [6]. Experts suggest that if a patient’s serum vitamin B12 level is between 150 to 399 pg/mL (111 to 294 pmol/L), the patient’s serum MMA levels should be checked to help confirm a diagnosis of vitamin B12 deficiency [7,9].

Where did MEDucated get this?

Vitamin B12 — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Assessing Vitamin B12 Status
ODS revision: July 2, 2025
Retrieved: 2026-08-10T22:07:05.257Z
Source fingerprint: a488ce5e4f73cbe7a517bfad2bc6c15f8da92daa99709eca8b3c56aadea00ae8
Cited reference numbers: 2, 6, 7, 8, 9, 10, 11

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Vitamin D

Source-backed preview

Imported NIH ODS source content is available for this topic. MEDucated has preserved the source wording and has not converted it into personalized guidance.

Structural characterization

Evidence profile

No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 13 identified
Human evidence: Human evidence identified
Randomized trials: Randomized trials not identified in the frozen metadata
Reviews and meta-analyses: Systematic review or meta-analysis identified
Evidence recency: 2007–2024
Source-described consistency: Not characterized in these source blocks
MEDucated evidence rating: Not assigned

Reference counts describe frozen source associations; a larger count does not establish stronger evidence.

Inspect technical evidence details

Evidence types identified

Government reference1
Study type could not be determined9
Clinical guideline2
Systematic review1

Source-described limitations

No explicit limitation phrase was identified in these imported source blocks.

Classified references

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
Government reference · Population basis: unknown · Directness: not assessed
Norman AW, Henry HH. Vitamin D. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition, 10th ed. Washington DC: Wiley-Blackwell, 2012.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Jones G. Vitamin D. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease, 11th ed. Philadelphia: Lippincott Williams & Wilkins, 2014.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Sempos CT, Heijboer AC, Bikle DD, Bollerslev J, Bouillon R, Brannon PM, et al. Vitamin D assays and the definition of hypovitaminosis D. Results from the First International Conference on Controversies in Vitamin D. Br J Clin Pharmacol 2018;84:2194-207. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
LeFevre ML. Screening for vitamin deficiency in adults: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2015;162:133-40. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Brooks SPJ, Sempos CT. The importance of 25-hydroxyvitamin D assay standardization and the Vitamin D Standardization Program. Journal of AOAC International 2017;100:1223-4.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Taylor CL, Sempos CT, Davis CD, Brannon PM. Vitamin D: moving forward to address emerging science. Nutrients 2017, 9, 1308; doi:10.3390/mu9121308. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Sempos CT, Binkley N. 25-hydroxyvitamin D assay standardisation and vitamin D guidelines paralysis. Public Health Nutrition 2020;23:1153-64. [PubMed abstract]
Clinical guideline · Population basis: unknown · Directness: not assessed
Office of Dietary Supplements, National Institutes of Health. Vitamin D Standardization Program (VDSP).
Study type could not be determined · Population basis: unknown · Directness: not assessed
Demay MB, Pittas AG, Bikle DD, Diab DL, Kiely ME, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2024 Jul 12;109(8):1907-1947. [PubMed abstract]
Clinical guideline · Population basis: unknown · Directness: not assessed
Shah VP, Nayfeh T, Alsawaf Y, Saadi S, Farah M, et al. A Systematic Review Supporting the Endocrine Society Clinical Practice Guidelines on Vitamin D. J Clin Endocrinol Metab. 2024 Jul 12;109(8):1961-1974. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed
Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Brown LL, Cohen B, Tabor D, Zappala G, Maruvada P, Coates PM. The vitamin D paradox in Black Americans: A systems-based approach to investigating clinical practice, research, and public health—expert panel meeting report. BMC Proceedings, 2018;12(Suppl 6):6. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Read imported source wording for Vitamin D

Serum concentration of 25(OH)D is the main indicator of vitamin D status. However, the serum concentrations of 25(OH)D that are associated with vitamin D deficiency have not been definitively identified. The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine states that levels of 50 nmol/L (20 ng/mL) or more are sufficient for most people, and that the risk of deficiency increases at serum concentrations of less than 30 nmol/L (12 ng/mL).

Serum concentration of 25(OH)D is currently the main indicator of vitamin D status. It reflects vitamin D produced endogenously and that obtained from foods and supplements [1]. In serum, 25(OH)D has a fairly long circulating half-life of 15 days [1]. Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL). One nmol/L is equal to 0.4 ng/mL, and 1 ng/mL is equal to 2.5 nmol/L.

Assessing vitamin D status by measuring serum 25(OH)D concentrations is complicated by the considerable variability of the available assays (the two most common ones involve antibodies or chromatography) used by laboratories that conduct the analyses [5,6]. As a result, a finding can be falsely low or falsely high, depending on the assay used and the laboratory. The international Vitamin D Standardization Program has developed procedures for standardizing the laboratory measurement of 25(OH)D to improve clinical and public health practice [5,7-10].

In contrast to 25(OH)D, circulating 1,25(OH)2D is generally not a good indicator of vitamin D status because it has a short half-life measured in hours, and serum levels are tightly regulated by parathyroid hormone, calcium, and phosphate [1]. Levels of 1,25(OH)2D do not typically decrease until vitamin D deficiency is severe [2].

Although 25(OH)D functions as a biomarker of exposure, the extent to which 25(OH)D levels also serve as a biomarker of effect on the body (i.e., relating to health status or outcomes) is not clear [1,3].

Researchers have not definitively identified serum concentrations of 25(OH)D associated with deficiency (e.g., rickets), adequacy for bone health, and overall health. After reviewing data on vitamin D needs, an expert committee of the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine (NASEM) concluded that people are at risk of vitamin D deficiency at serum 25(OH)D concentrations less than 30 nmol/L (12 ng/mL; see Table 1 for definitions of deficiency and inadequacy) [1]. Some people are potentially at risk of inadequacy at 30 to 50 nmol/L (12–20 ng/mL). Levels of 50 nmol/L (20 ng/mL) or more are sufficient for most people. The FNB also noted that serum concentrations greater than 125 nmol/L (50 ng/mL) can be associated with adverse effects [1] (Table 1). The Endocrine Society has not identified 25(OH)D concentrations associated with vitamin D sufficiency, insufficiency, and deficiency and does not recommend routine testing of 25(OH)D concentrations in healthy individuals [11,12].

Table 1: Serum 25-Hydroxyvitamin D [25(OH)D] Concentrations and Health [1]
nmol/L*	ng/mL*	Health status
<30	<12	Associated with vitamin D deficiency, which can lead to rickets in infants and children and osteomalacia in adults
30 to <50	12 to <20	Generally considered inadequate for bone and overall health in healthy individuals
≥50	≥20	Generally considered adequate for bone and overall health in healthy individuals
>125	>50	Linked to potential adverse effects, particularly at >150 nmol/L (>60 ng/mL)
*Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL). One nmol/L = 0.4 ng/mL, and 1 ng/mL = 2.5 nmol/L.

Optimal serum concentrations of 25(OH)D for bone and general health have not been established because they are likely to vary by stage of life, by race and ethnicity, and with each physiological measure used [1,13,14]. In addition, although 25(OH)D levels rise in response to increased vitamin D intake, the relationship is nonlinear [1]. The amount of increase varies, for example, by baseline serum levels and duration of supplementation.

Where did MEDucated get this?

Vitamin D — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements. Government health-professional reference material imported without MEDucated medical review.

Source section: Assessing vitamin D status
ODS revision: June 27, 2025
Retrieved: 2026-08-10T22:07:04.753Z
Source fingerprint: 825b1a553a4a177e2d87fc412b0b4b21daa72ca92f4334a0096bc0dfa7f70a3c
Cited reference numbers: 1, 5, 6, 7, 8, 9, 10, 2, 3, 11, 12, 13, 14

Inspect the official NIH ODS source

Source attribution does not imply NIH or ODS endorsement of MEDucated.

Evidence topic

Regulatory information

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Evidence topic

Evidence limitations

Unavailable for both

Vitamin B12

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.

Vitamin D

Evidence unavailable

No source-backed evidence is currently available for this topic in MEDucated.

The attached ODS revision does not provide an imported source section for this topic.