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Calcium

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Calcium carbonatemineral compound
Calcium citratemineral compound

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Evidence source: NIH ODS evidence synthesis
Linked references: 3 identified
Human evidence: Human evidence not identified in the frozen metadata
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Evidence recency: 2010–2014
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Government reference1
Study type could not be determined2

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Classified references

Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press; 2011.
Government reference · Population basis: unknown · Directness: not assessed
Heaney RP. Calcium. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:101-6.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Weaver CM, Heaney RP. Calcium. 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; 2014:133-49.
Study type could not be determined · Population basis: unknown · Directness: not assessed

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Calcium, the most abundant mineral in the body, is found in some foods, added to others, present in some medicines (such as antacids), and available as a dietary supplement.

Calcium makes up much of the structure of bones and teeth and allows normal bodily movement by keeping tissue rigid, strong, and flexible [1]. The small ionized pool of calcium in the circulatory system, extracellular fluid, and various tissues mediates blood vessel contraction and dilation, muscle function, blood clotting, nerve transmission, and hormonal secretion [1,2].

Calcium from foods and dietary supplements is absorbed by both active transport and by passive diffusion across the intestinal mucosa [1,3]. Active transport is responsible for most absorption when calcium intakes are lower, and passive diffusion accounts for an increasing proportion of calcium absorption as intakes rise. Vitamin D is required for calcium to be absorbed in the gut by active transport and to maintain adequate calcium levels in the blood [1].

Where did MEDucated get this?

Calcium — 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 22, 2026
Retrieved: 2026-08-10T22:07:09.182Z
Source fingerprint: 5139a098b618d4d9810942614ee016aa45b5a58c35e89d7a588a9d7d93a4f2f7
Cited reference numbers: 1, 2, 3

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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: 2006–2020
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Government reference1
Study type could not be determined6
Systematic review1
Meta-analysis2
Randomized controlled trial2
Narrative review1

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Classified references

Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press; 2011.
Government reference · Population basis: unknown · Directness: not assessed
Weaver CM. Calcium. In: Marriott BP, Birt DF, Stallings VA, Yates AA, eds. Present Knowledge in Nutrition. 11th ed. Cambridge, Massachusetts: Wiley-Blackwell; 2020:321-48.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Kahwati LC, Weber RP, Pan H, Gourlay M, LeBlanc E, Coker-Schwimmer M, et al. Vitamin D, calcium, or combined supplementation for the primary prevention of fractures in community-dwelling adults: evidence report and systematic review for the US Preventive Services Task Force. Jama 2018;319:1600-12. [PubMed abstract]
Systematic review · Population basis: human · Directness: not assessed
Asemi Z, Saneei P, Sabihi SS, Feizi A, Esmaillzadeh A. Total, dietary, and supplemental calcium intake and mortality from all- causes, cardiovascular disease, and cancer: A meta-analysis of observational studies. Nutr Metab Cardiovasc Dis 2015;25:623-34. [PubMed abstract]
Meta-analysis · Population basis: unknown · Directness: not assessed
Kesse E, Bertrais S, Astorg P, Jaouen A, Arnault N, Galan P, et al. Dairy products, calcium and phosphorus intake, and the risk of prostate cancer: results of the French prospective SU.VI.MAX (Supplementation en Vitamines et Mineraux Antioxydants) study. Br J Nutr 2006;95:539-45. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Aune D, Navarro Rosenblatt DA, Chan DS, Vieira AR, Vieira R, Greenwood DC, et al. Dairy products, calcium, and prostate cancer risk: a systematic review and meta-analysis of cohort studies. Am J Clin Nutr 2015;101:87-117. [PubMed abstract]
Meta-analysis · Population basis: unknown · Directness: not assessed
Chen Y, Strasser S, Cao Y, Wang KS, Zheng S. Calcium intake and hypertension among obese adults in United States: associations and implications explored. J Hum Hypertens 2015;29:541-7. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Cormick G, Ciapponi A, Cafferata ML, Belizán JM. Calcium supplementation for prevention of primary hypertension. Cochrane Database of Systematic Reviews 2015. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Donneyong MM, Hornung CA, Taylor KC, Baumgartner RN, Myers JA, Eaton CB, et al. Risk of heart failure among postmenopausal women: a secondary analysis of the randomized trial of vitamin D plus calcium of the women's health initiative. Circ Heart Fail 2015;8:49-56. [PubMed abstract]
Randomized controlled trial · Population basis: human · Directness: not assessed
Boursiquot BC, Larson JC, Shalash OA, Vitolins MZ, Soliman EZ, Perez MV. Vitamin D with calcium supplementation and risk of atrial fibrillation in postmenopausal women. Am Heart J 2019;209:68-78. [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;354:669-83. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Wallace RB, Wactawski-Wende J, O'Sullivan MJ, Larson JC, Cochrane B, Gass M, et al. Urinary tract stone occurrence in the Women's Health Initiative (WHI) randomized clinical trial of calcium and vitamin D supplements. Am J Clin Nutr 2011;94:270-7. [PubMed abstract]
Randomized controlled trial · Population basis: human · Directness: not assessed
Candelas G, Martinez-Lopez JA, Rosario MP, Carmona L, Loza E. Calcium supplementation and kidney stone risk in osteoporosis: a systematic literature review. Clin Exp Rheumatol 2012;30:954-61. [PubMed abstract]
Narrative review · Population basis: unknown · Directness: not assessed

Higher intakes of supplemental calcium might increase the risk of kidney stones. According to some research, calcium supplements have the potential to increase the risk of cardiovascular disease. Higher calcium intakes might also increase the risk of prostate cancer. The tolerable upper intake level for calcium ranges from 2,000 mg to 2,500 mg for adults and from 1,000 mg to 3,000 mg for infants, children, and adolescents, depending on age.

UL reference intakeSource-described amount

Hypercalcemia (serum levels >10.5 mg/dL [2.63 mmol/L]) and hypercalciuria (urinary calcium levels >250 mg/day in women and 275 mg/day in men) are rare in healthy people and usually result from cancer, primary hyperparathyroidism, and other conditions [1,4]. Hypercalcemia and hypercalciuria can cause poor muscle tone, renal insufficiency, hypophosphatemia, constipation, nausea, weight loss, fatigue, polyuria, heart arrhythmias, and a higher risk of CVD mortality [1,4,49].

Source-described amount

High calcium intakes might also increase the risk of CVD (see the section on CVD in Calcium and Health section above) [39,63,68,70,71] and prostate cancer (see the Other Cancers in Calcium and Health section above for more details) [58,59], although not all studies confirm these findings.

The ULs for calcium established by the FNB are listed in Table 3. They are based on observational evidence from the WHI showing a link between higher intakes of supplemental calcium (1,000 mg/day for 7 years) and a greater risk of kidney stones [97,98]. However, two subsequent systematic reviews of the evidence from 10 studies in more than 8,000 adults with osteoporosis who took 120 to 1,500 mg supplemental calcium daily for 3 days to 3 years [99] and 11 RCTs in 51,419 adults 50 years and older who took 1,000 to 1,600 mg calcium with or without vitamin D for 2 to 7 years [39] found no such association.

Source intake rangeSource-described amount

Table 3: Tolerable Upper Intake Levels (ULs) for Calcium in Milligrams (mg) [1]
Age	Male	Female	Pregnant	Lactating
0–6 months	1,000 mg	1,000 mg
7–12 months	1,500 mg	1,500 mg
1–3 years	2,500 mg	2,500 mg
4–8 years	2,500 mg	2,500 mg
9–13 years	3,000 mg	3,000 mg
14–18 years	3,000 mg	3,000 mg	3,000 mg	3,000 mg
19–50 years	2,500 mg	2,500 mg	2,500 mg	2,500 mg
51–70 years	2,000 mg	2,000 mg
>70 years	2,000 mg	2,000 mg

UL reference intakeSource-described amount

Where did MEDucated get this?

Calcium — 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 Calcium
ODS revision: June 22, 2026
Retrieved: 2026-08-10T22:07:09.182Z
Source fingerprint: 5139a098b618d4d9810942614ee016aa45b5a58c35e89d7a588a9d7d93a4f2f7
Cited reference numbers: 1, 4, 49, 39, 58, 59, 63, 68, 70, 71, 97, 98, 99

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Side effects

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

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Evidence source: NIH ODS evidence synthesis
Linked references: 11 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: 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.

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Pharmacokinetic study1
Systematic review1
Regulatory source3
Study type could not be determined6

Source-described limitations

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

Classified references

Song I, Borland J, Arya N, Wynne B, Piscitelli S. Pharmacokinetics of dolutegravir when administered with mineral supplements in healthy adult subjects. J Clin Pharmacol 2015;55:490-6. [PubMed abstract]
Pharmacokinetic study · Population basis: human · Directness: not assessed
Jalloh MA, Gregory PJ, Hein D, Risoldi Cochrane Z, Rodriguez A. Dietary supplement interactions with antiretrovirals: a systematic review. Int J STD AIDS 2017;28:4-15 [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed
U.S. Food and Drug Administration. Tivicay Label. 2020.
Regulatory source · Population basis: unknown · Directness: not assessed
U.S. Food and Drug Administration. Dovato Label. 2019.
Regulatory source · Population basis: unknown · Directness: not assessed
Morini E, Catalano A, Lasco A, Morabito N, Benvenga S. L-thyroxine malabsorption due to calcium carbonate impairs blood pressure, total cholesterolemia, and fasting glycemia. Endocrine 2019;64:284-92. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Singh N, Singh PN, Hershman JM. Effect of calcium carbonate on the absorption of levothyroxine. Jama 2000;283:2822-5. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Schneyer CR. Calcium carbonate and reduction of levothyroxine efficacy. Jama 1998;279:750. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
U.S. Food and Drug Administration. LEVO-T Label. 2017.
Regulatory source · Population basis: unknown · Directness: not assessed
Jones BJ, Twomey PJ. Requesting patterns for serum calcium concentration in patients on long-term lithium therapy. Int J Clin Pract 2009;63:170-2. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Pletz MW, Petzold P, Allen A, Burkhardt O, Lode H. Effect of calcium carbonate on bioavailability of orally administered gemifloxacin. Antimicrob Agents Chemother 2003;47:2158-60. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Kays MB, Overholser BR, Mueller BA, Moe SM, Sowinski KM. Effects of sevelamer hydrochloride and calcium acetate on the oral bioavailability of ciprofloxacin. Am J Kidney Dis 2003;42:1253-9. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Calcium supplements may interact with medications, and some medications may affect calcium levels. These medications include dolutegravir, levothyroxine, lithium, and quinolone antibiotics.

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

Dolutegravir (Dovato, Tivicay) is an HIV integrase inhibitor used in adults and children. Concomitant use of calcium supplements and dolutegravir can reduce blood levels of dolutegravir substantially, apparently through chelation [100,101]. The labels approved by the FDA for dolutegravir advise patients to take dolutegravir 2 hours before or 6 hours after taking calcium supplements [102,103].

Calcium carbonate supplements can interfere with the absorption of levothyroxine (Synthroid, Levoxyl, and others), a thyroid hormone used to treat hypothyroidism and thyroid cancer [104-106]. The FDA-approved label for this medication instructs patients who are taking calcium carbonate supplements to avoid taking levothyroxine within 4 hours of taking the supplement [107].

Long-term use of lithium (Eskalith, Lithobid), a treatment for bipolar disorder, can lead to hypercalcemia, and use of both lithium and calcium supplements could increase this risk [108].

Simultaneous use of calcium supplements and quinolone antibiotics—such as ciprofloxacin (Cipro), gemifloxacin (Factive), and moxifloxacin (Avelox)—can reduce the absorption of quinolones [109,110]. Taking the antibiotic 2 hours before or 2 hours after calcium supplements prevents this effect [109].

Where did MEDucated get this?

Calcium — 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 22, 2026
Retrieved: 2026-08-10T22:07:09.182Z
Source fingerprint: 5139a098b618d4d9810942614ee016aa45b5a58c35e89d7a588a9d7d93a4f2f7
Cited reference numbers: 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110

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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: 1997–2021
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.

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Evidence types identified

Government reference2
Study type could not be determined3

Source-described limitations

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

Classified references

Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press; 2011.
Government reference · Population basis: unknown · Directness: not assessed
Weaver CM, Heaney RP. Calcium. 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; 2014:133-49.
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
Institute of Medicine SCotSEoDR, Intakes,. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academies Press; 1997.
Government reference · Population basis: unknown · Directness: not assessed
Heaney RP, Dowell MS, Barger-Lux MJ. Absorption of calcium as the carbonate and citrate salts, with some observations on method. Osteoporos Int 1999;9:19-23. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

Read imported source wording

Many dietary supplements contain calcium, usually in the form of calcium carbonate or calcium citrate. The percentage of calcium that is absorbed from supplements depends on a number of factors, including the form of the calcium and the total amount of elemental calcium consumed at one time.

Calcium is available in many dietary supplements, including multivitamin/mineral products and supplements containing calcium only or calcium plus vitamin D [14]. The amounts of calcium in supplements vary widely; multivitamin/mineral supplements commonly contain about 200 to 300 mg, and common amounts in calcium or calcium plus vitamin D supplements are 500 or 600 mg [14].

Source intake rangeSource-described amount

The two most common forms of calcium in supplements are calcium carbonate and calcium citrate [1]. In people with low levels of stomach acid, the solubility rate of calcium carbonate is lower, which could reduce the absorption of calcium from calcium carbonate supplements unless they are taken with a meal [3]. Calcium citrate is less dependent on stomach acid for absorption than calcium carbonate, so it can be taken without food [1]. In general, however, absorption of calcium supplements is greater when they are taken with food, regardless of whether the user’s gastric acid is low [3]. Other calcium forms in supplements include calcium sulfate, ascorbate, microcrystalline hydroxyapatite, gluconate, lactate, and phosphate [14].

The forms of calcium in supplements contain varying amounts of elemental calcium. For example, calcium carbonate is 40% calcium by weight, whereas calcium citrate is 21% calcium [1]. Elemental calcium is listed in the Supplement Facts panel, so consumers do not need to calculate the amount of calcium supplied by various forms of calcium in supplements.

The percentage of calcium absorbed from supplements, as with that from foods, depends not only on the source of calcium but also on the total amount of elemental calcium consumed at one time; as the amount increases, the percentage absorbed decreases. Absorption from supplements is highest with doses of 500 mg or less [15]. For example, the body absorbs about 36% of a 300 mg calcium dose and 28% of a 1,000 mg dose [16].

Source-described amount

Some individuals who take calcium supplements might experience gastrointestinal side effects, including gas, bloating, constipation, or a combination of these symptoms. Calcium carbonate appears to cause more of these side effects than calcium citrate, especially in older adults who have lower levels of stomach acid [1]. Symptoms can be alleviated by switching to a supplement containing a different form of calcium, taking smaller calcium doses more often during the day, or taking the supplement with meals.

Where did MEDucated get this?

Calcium — 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 22, 2026
Retrieved: 2026-08-10T22:07:09.182Z
Source fingerprint: 5139a098b618d4d9810942614ee016aa45b5a58c35e89d7a588a9d7d93a4f2f7
Cited reference numbers: 14, 1, 3, 15, 16

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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: 2011–2011
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.

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Government reference1

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Classified references

Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press; 2011.
Government reference · Population basis: unknown · Directness: not assessed

Read imported source wording

The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine has established Recommended Dietary Allowances and Adequate Intakes for calcium. These values range from 1,000 to 1,200 mg for adults and from 200 to 1,300 mg for infants, children, and adolescents, depending on age.

RDA reference intakeAI reference intakeSource intake rangeSource-described amount

Intake recommendations for calcium 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 calcium [1]. For adults, the main criterion that the FNB used to establish the RDAs was the amount needed to promote bone maintenance and neutral calcium balance. For infants age 0 to 12 months, the FNB established an AI that is equivalent to the mean intake of calcium in healthy, breastfed infants. For children and adolescents, the RDAs are based on intakes associated with bone accumulation and positive calcium balance.

AI reference intake

Table 1: Recommended Dietary Allowances (RDAs) for Calcium in Milligrams (mg) [1]
Age	Male	Female	Pregnant	Lactating
0–6 months*	200 mg	200 mg
7–12 months*	260 mg	260 mg
1–3 years	700 mg	700 mg
4–8 years	1,000 mg	1,000 mg
9–13 years	1,300 mg	1,300 mg
14–18 years	1,300 mg	1,300 mg	1,300 mg	1,300 mg
19–50 years	1,000 mg	1,000 mg	1,000 mg	1,000 mg
51–70 years	1,000 mg	1,200 mg
>70 years	1,200 mg	1,200 mg

RDA reference intakeSource-described amount

*Adequate Intake (AI)

AI reference intake

Where did MEDucated get this?

Calcium — 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 22, 2026
Retrieved: 2026-08-10T22:07:09.182Z
Source fingerprint: 5139a098b618d4d9810942614ee016aa45b5a58c35e89d7a588a9d7d93a4f2f7
Cited reference numbers: 1

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No overall rating assigned

Evidence source: NIH ODS evidence synthesis
Linked references: 6 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: 2011–2021
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 determined3
Meta-analysis1
Systematic review1

Source-described limitations

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

Classified references

Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press; 2011.
Government reference · Population basis: unknown · Directness: not assessed
Weaver CM, Heaney RP. Calcium. 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; 2014:133-49.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Tai V, Leung W, Grey A, Reid IR, Bolland MJ. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ 2015;351:h4183. [PubMed abstract]
Meta-analysis · Population basis: unknown · Directness: not assessed
Cano A, Chedraui P, Goulis DG, Lopes P, Mishra G, Mueck A, et al. Calcium in the prevention of postmenopausal osteoporosis: EMAS clinical guide. Maturitas 2018;107:7-12. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Boaventura RM, Mendonca RB, Fonseca FA, Mallozi M, Souza FS, Sarni ROS. Nutritional status and food intake of children with cow's milk allergy. Allergol Immunopathol (Madr) 2019;47:544-50. [PubMed abstract]
Study type could not be determined · Population basis: human · Directness: not assessed
Bakaloudi DR, Halloran A, Rippin HL, Oikonomidou AC, Dardavesis TI, Williams J, et al. Intake and adequacy of the vegan diet. A systematic review of the evidence. Clin Nutr 2021;40:3503-21. [PubMed abstract]
Systematic review · Population basis: unknown · Directness: not assessed

Read imported source wording

Certain groups of people are more likely than others to have calcium inadequacy. These include postmenopausal women and individuals who avoid dairy products.

The following groups are among those most likely to get inadequate amounts of calcium.

Menopause leads to bone loss because decreases in estrogen production reduce calcium absorption and increase urinary calcium loss and calcium resorption from bone [1]. On average, women lose approximately 1% of their bone mineral density (BMD) per year after menopause [25]. Over time, these changes lead to decreased bone mass and fragile bones [1]. About 30% of postmenopausal women in the United States and Europe have osteoporosis, and at least 40% of those with this condition develop at least one fragility fracture (a fracture that occurs after minor trauma, such as a fall from standing height or lower) [26]. The calcium RDA is 1,200 mg for women older than 50 years (vs. 1,000 mg for younger women) to lessen bone loss after menopause [1].

RDA reference intakeSource-described amount

People with lactose intolerance, those with an allergy to milk, and those who avoid eating dairy products (including vegans) have a higher risk of inadequate calcium intakes because dairy products are rich sources of calcium [1,27]. Options for increasing calcium intakes in individuals with lactose intolerance include consuming lactose-free or reduced-lactose dairy products, which contain the same amounts of calcium as regular dairy products [1,3]. Those who avoid dairy products because of allergies or for other reasons can obtain calcium from nondairy sources, such as some vegetables, canned fish with bones, or fortified foods [1]. However, these individuals typically need to eat foods fortified with calcium or take supplements to obtain recommended amounts [28].

Where did MEDucated get this?

Calcium — 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 Calcium Inadequacy
ODS revision: June 22, 2026
Retrieved: 2026-08-10T22:07:09.182Z
Source fingerprint: 5139a098b618d4d9810942614ee016aa45b5a58c35e89d7a588a9d7d93a4f2f7
Cited reference numbers: 1, 25, 26, 3, 27, 28

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Government reference1
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Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press; 2011.
Government reference · Population basis: unknown · Directness: not assessed
Weaver CM, Heaney RP. Calcium. 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; 2014:133-49.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Weaver CM. Calcium. In: Marriott BP, Birt DF, Stallings VA, Yates AA, eds. Present Knowledge in Nutrition. 11th ed. Cambridge, Massachusetts: Wiley-Blackwell; 2020:321-48.
Study type could not be determined · Population basis: unknown · Directness: not assessed
Wawrzyniak N, Suliburska J. Nutritional and health factors affecting the bioavailability of calcium: a narrative review. Nutr Rev 2021. [PubMed abstract]
Narrative review · Population basis: unknown · Directness: not assessed
Fairweather-Tait SJ, Teucher B. Iron and calcium bioavailability of fortified foods and dietary supplements. Nutr Rev 2002;60:360-7. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed
Song L. Calcium and bone metabolism indices. Adv Clin Chem 2017;82:1-46. [PubMed abstract]
Study type could not be determined · Population basis: unknown · Directness: not assessed

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Because almost all calcium in the body is stored in the skeleton, a dual x-ray absorptiometry scan of bone mineral density can assess a person’s cumulative calcium status over their lifetime. Total calcium levels can be measured in serum or plasma, but these levels are not a good reflection of an individual’s calcium status.

Almost all calcium in the body (98%) is stored in the bones, and the body uses the bones as a reservoir for, and source of, calcium to maintain calcium homeostasis [1]. More than 99% of calcium in the body is in the form of calcium hydroxyapatite, an inorganic matrix of calcium and phosphate that is stored in the bones and teeth [1,4,5]. Unlike teeth, bone undergoes continuous remodeling, with constant resorption and deposition of calcium into new bone [4]. Bone remodeling is required to change bone size during growth, repair damage, maintain serum calcium levels, and provide a source of other minerals [4].

At birth, the body contains about 26 to 30 grams (g) calcium. This amount rises quickly after birth, reaching about 1,200 g in women and 1,400 g in men by adulthood [1]. These levels remain constant in men, but they start to drop in women as a result of increases in bone remodeling due to decreased estrogen production at the start of menopause [1].

Source-described amount

An inverse relationship exists between calcium intake and absorption. Absorption of calcium from food is about 45% at intakes of 200 milligrams (mg)/day but only 15% when intakes are higher than 2,000 mg/day [6]. Age can also affect the absorption of dietary calcium [1,4]. Net absorption of dietary calcium is as high as 60% in infants and young children, who need substantial amounts to build bone, but it decreases to about 25% in adulthood and continues to decline with age [1].

Source-described amount

Total calcium levels can be measured in serum or plasma; serum levels are typically 8.8 to 10.4 mg/deciliter (dL) (2.2 to 2.6 millimoles per liter [mmol/L]) in healthy people [1,7]. However, serum levels do not reflect nutritional status because of their tight homeostatic control [4]. Levels of ionized (or free) calcium, the biologically active form, in serum are also used to measure calcium status. The normal range of ionized calcium in healthy people is 4.6 to 5.3 mg/dL (1.15 to 1.33 mmol/L) [7]. Dual x-ray absorptiometry testing of bone mineral density can be used to assess cumulative calcium status over the lifetime because the skeleton stores almost all calcium in the body [3].

Source intake rangeSource-described amount

Where did MEDucated get this?

Calcium — Fact Sheet for Health Professionals

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

Source section: Assessing calcium status
ODS revision: June 22, 2026
Retrieved: 2026-08-10T22:07:09.182Z
Source fingerprint: 5139a098b618d4d9810942614ee016aa45b5a58c35e89d7a588a9d7d93a4f2f7
Cited reference numbers: 1, 4, 5, 6, 3, 7

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Fixture ID: fixture:supplement:calcium:ods-evidence-preview
Fixture revision: source-revision:nih-ods:calcium-health-professional:2026-08-10.5139a098b618
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Calcium — Fact Sheet for Health Professionals

NIH Office of Dietary Supplements

Fixture ID: fixture:supplement:calcium:ods-evidence-preview
Fixture revision: source-revision:nih-ods:calcium-health-professional:2026-08-10.5139a098b618
Content classification: source backed demonstration
Medical review: not medically reviewed
Evidence classification: government reference
External source metadata: Available in source inspection