Calcium

    Written by:
    Daryl Nault

    Fact-checked

    by:

    Giulia Guerrini, Conni Covington
    Last Updated: May 28, 2025

    Calcium is a macromineral that can be obtained through the diet, particularly in dairy products and, to a lesser extent, vegetables. It’s primarily used to support bone health, and there is some evidence that it supports cardiovascular health and women’s health.

    What is calcium?

    Calcium is an essential macromineral, meaning that it's needed in large amounts relative to other minerals. It is arguably the most notable nutrient for bone health.[6][7] Among its various functions in the body, calcium is typically associated with the formation and metabolism of bone.

    Over 99% of total body calcium is found in the bones and teeth, predominantly as calcium hydroxyapatite, which is critical for bone structure and strength.[6][7][8] The remaining 1% of bodily calcium resides in extracellular fluids (plasma) or soft tissue, where it aids in cellular signaling.[9][6][7][10]

    What are calcium’s main benefits?

    Supplementing calcium with vitamin D can reduce the risk of fractures in older adults.[11][12][13] For people under the age of 35, calcium supplementation may still be beneficial in increasing bone mineral density, especially if they have inadequate dietary calcium intake.[14][1]

    Calcium supplementation may also be beneficial for cardiovascular health, particularly with regards to reducing blood pressure in all ages.[15][16] The positive effects of calcium supplementation for both blood pressure and bone health can also be seen in individuals who are pregnant or looking to conceive, with added effects that could potentially reduce the risks associated with or prevent gestational diabetes.[17][18][19][20]

    Some meta-analyses have also indicated that calcium supplementation could aid in endocrine or metabolic related health as well. In individuals with or at risk of metabolic disorders, calcium appears to modestly reduce BMI, waist circumference, body fat, triglycerides, and total cholesterol.[21][22][23][24] Calcium supplementation in conjunction with vitamin D and metformin, may also improve some signs and symptoms in people who have PCOS.[25]

    Does calcium affect bone health?Does calcium affect cardiometabolic health?Does calcium affect women’s health?

    How does calcium work?

    Bone integrity depends on cycles of bone formation by cells called osteoblasts and resorption by osteoclasts. If the cycle falls out of balance toward excessive resorption, conditions like osteoporosis or rickets may occur.[26] During bone formation, osteoblasts lay a foundation for hydroxyapatite crystals to be deposited into, thus hardening the bone structure. In this sense, stored calcium contributes to skeletal integrity, but it may also act as a reserve for release into the bloodstream when needed elsewhere.[2]

    Calcium-sensing receptors in the kidneys, thyroid, and parathyroid respond to fluctuating calcium concentrations in an effort to maintain balance.[27] Interestingly, inflammation, particularly interleukin 6 and interleukin 1-beta, is thought to increase the number of calcium-sensing receptors available.[28][29][27] When blood calcium levels get too high, the hormone calcitonin is released by the thyroid, which inhibits calcium uptake and resorption and lowers serum calcium through increased urinary excretion.[2]

    Symptoms and severity scores of hypercalcemia

    image

    When blood calcium levels fall too low, parathyroid hormone is released, which signals osteoclasts to release stored calcium from the bone into the system. Parathyroid hormone also influences the kidneys to increase calcium resorption and secrete vitamin D3. Vitamin D3 then enhances intestinal absorption of supplemental or dietary calcium.[2][27] Once free in the system, calcium serves as a cofactor for activities like blood clotting, a trigger for responses like muscle contraction or nerve signals, and a stabilizer of the phospholipids in cellular membranes.[2]

    What are other names for Calcium?

    Note that Calcium is also known as:

    • Elemental calcium
    • Ca2+
    • Ca
    • Calcium carbonate
    • Calcium citrate
    • Coral calcium
    • Calcium phosphate
    • Calcium gluconate
    • Calcium lactate

    Dosage information

    Formulation:

    Supplemental calcium is usually recommended when dietary calcium is insufficient, and it is most frequently found as calcium carbonate and calcium citrate.[1][2] Forms of calcium supplements that may also be available include calcium phosphate, calcium lactate, calcium gluconate, and coral calcium.[1] Different forms of oral calcium supplements have their own benefits and drawbacks. Coral calcium and calcium citrate, for example, may be better absorbed than calcium carbonate. Calcium carbonate is, on the other hand, less expensive than other forms, making it more accessible.[3][4] Standalone calcium citrate supplements may be more readily used by the body than calcium carbonate. The exception to this seems to be in calcium-fortified foods, where calcium carbonate is absorbed better.[5]

    Range of dosages studied:

    Current meta-analyses have reported on studies that cover a wide range of calcium supplementation dosages, from a low dose of 162 mg per day all the way up to 7,700 mg per day. In many of these studies, calcium was taken with vitamin D3 ranging from 400 to 1,000 IU per day. Ranges studied for skeletal health, pregnancy-related concerns, digestion, metabolism, and body mass are similar (about 200 to 2,000 mg per day), but cardiovascular health uses a higher range (500 to 7,700 mg per day).

    Frequently asked questions

    What is calcium?

    Calcium is an essential macromineral, meaning that it's needed in large amounts relative to other minerals. It is arguably the most notable nutrient for bone health.[6][7] Among its various functions in the body, calcium is typically associated with the formation and metabolism of bone.

    Over 99% of total body calcium is found in the bones and teeth, predominantly as calcium hydroxyapatite, which is critical for bone structure and strength.[6][7][8] The remaining 1% of bodily calcium resides in extracellular fluids (plasma) or soft tissue, where it aids in cellular signaling.[9][6][7][10]

    What are calcium’s main benefits?

    Supplementing calcium with vitamin D can reduce the risk of fractures in older adults.[11][12][13] For people under the age of 35, calcium supplementation may still be beneficial in increasing bone mineral density, especially if they have inadequate dietary calcium intake.[14][1]

    Calcium supplementation may also be beneficial for cardiovascular health, particularly with regards to reducing blood pressure in all ages.[15][16] The positive effects of calcium supplementation for both blood pressure and bone health can also be seen in individuals who are pregnant or looking to conceive, with added effects that could potentially reduce the risks associated with or prevent gestational diabetes.[17][18][19][20]

    Some meta-analyses have also indicated that calcium supplementation could aid in endocrine or metabolic related health as well. In individuals with or at risk of metabolic disorders, calcium appears to modestly reduce BMI, waist circumference, body fat, triglycerides, and total cholesterol.[21][22][23][24] Calcium supplementation in conjunction with vitamin D and metformin, may also improve some signs and symptoms in people who have PCOS.[25]

    Does calcium affect bone health?

    According to meta-analyses of randomized controlled trials, supplementing with calcium (500 to 1,200 mg per day) and vitamin D (400 to 800 IU per day) can reduce the risk of fractures, especially hip fractures, in adults who are at least 50 years old.[11][12][13] Additionally, the magnitude of benefit is greater in older (age ≥80) than younger (age <80) adults and among adults living in long-term care facilities than adults who live in the community.[13]

    In people under the age of 35, calcium supplementation (200 to 2,000 mg per day) can improve total body bone mineral density (BMD), and it seems to be particularly effective in increasing the BMD of the femoral neck relative to other sites.[14] Additionally, the magnitude of benefit is greater in people with inadequate calcium intake at baseline. Adequate calcium intake is fundamental to promoting and maintaining bone health, but like other nutrients, supplemental calcium will improve bone health only if dietary calcium intake is inadequate.[1]

    There has been some concern of risk of cardiovascular disease when supplementing with calcium. However, in meta-analyses of adults at a higher risk of conditions related to calcium insufficiency (e.g., postmenopausal women, those with low-trauma fractures, mobile elderly), calcium supplementation (500 to 2,000 mg per day, over durations of 1.5 to 11.9 years) was not found to be associated with an increased risk of cardiovascular events or death.[30]

    Does calcium affect cardiometabolic health?

    Meta-analyses have found that calcium may provide some cardiovascular benefit for adults with hypertension, lowering diastolic blood pressure, but not systolic blood pressure or heart rate, when taken in doses from 1 to 7.7 grams per day for durations ranging from one to 48 weeks.[15] Even adults and children with normal blood pressure could see mild reductions in blood pressure from adequate calcium intake (500 to 2,000 mg per day for durations of 3.5 months to 4 years). These effects were more pronounced, however, in people younger than 35, with dietary supplementation (vs. capsules or tablets), and/or between 1,000 and 1,500 mg per day.[16]

    There is also some evidence that calcium supplementation (162 to 2,000 mg per day, both as tablets and dietary fortification, over 3 to 24 months’ duration) aids in weight management and metabolism. When taken by people with or at risk of health conditions associated with increased body weight or metabolic dysfunction, calcium supplementation has demonstrated mild effects toward reducing BMI, waist circumference, body fat mass, risk of metabolic syndrome, triglyceride levels, and total cholesterol levels.[21] [22][23][24]

    Does calcium affect women’s health?

    For individuals who are pregnant or looking to conceive, calcium supplementation (300 to 2,000 mg per day over 6 to 22 months’ duration) has shown beneficial effects for avoiding hypertension as well as preventing the loss of bone mineral density. Taken in combination with vitamin D3 (400 to 1,000 IU per day), calcium supplementation could also help with the maintenance of circulating glucose and insulin levels.[17][18][19][20]

    How does calcium work?

    Bone integrity depends on cycles of bone formation by cells called osteoblasts and resorption by osteoclasts. If the cycle falls out of balance toward excessive resorption, conditions like osteoporosis or rickets may occur.[26] During bone formation, osteoblasts lay a foundation for hydroxyapatite crystals to be deposited into, thus hardening the bone structure. In this sense, stored calcium contributes to skeletal integrity, but it may also act as a reserve for release into the bloodstream when needed elsewhere.[2]

    Calcium-sensing receptors in the kidneys, thyroid, and parathyroid respond to fluctuating calcium concentrations in an effort to maintain balance.[27] Interestingly, inflammation, particularly interleukin 6 and interleukin 1-beta, is thought to increase the number of calcium-sensing receptors available.[28][29][27] When blood calcium levels get too high, the hormone calcitonin is released by the thyroid, which inhibits calcium uptake and resorption and lowers serum calcium through increased urinary excretion.[2]

    Symptoms and severity scores of hypercalcemia

    image

    When blood calcium levels fall too low, parathyroid hormone is released, which signals osteoclasts to release stored calcium from the bone into the system. Parathyroid hormone also influences the kidneys to increase calcium resorption and secrete vitamin D3. Vitamin D3 then enhances intestinal absorption of supplemental or dietary calcium.[2][27] Once free in the system, calcium serves as a cofactor for activities like blood clotting, a trigger for responses like muscle contraction or nerve signals, and a stabilizer of the phospholipids in cellular membranes.[2]

    Research Breakdown