Calcium

What is Calcium?

Calcium is the most plentiful mineral in the body. About 98% of it is stored in bones, which the body uses as a reserve to keep blood calcium steady.^[1]

Its role in the body

• Builds and maintains bones and teeth.^[1]
• Needed for muscles to contract, nerves to send signals, blood vessels to work and hormones to be released.^[1]

Important food sources

• Milk, curd (dahi), buttermilk and paneerAmong the richest and most easily absorbed sources.
• Ragi (finger millet)A traditional millet known for its calcium content; a verified value is not yet in our food list.
• Sesame seeds (til)USDA lists about 975 mg per 100 g for whole dried seeds; usual portions are small.
• Amaranth leaves (chaulai), drumstick (moringa) leaves and other green leafy vegetablesSpinach contains calcium but very little of it is absorbed because of oxalic acid.
• Tofu set with calcium saltsUSDA lists about 683 mg per 100 g for firm tofu made with calcium sulphate.
• Rajma, chana and other pulsesSmaller amounts.

Recommended dietary intake

Signs sometimes associated with low levels

• Low calcium intake over many years can lead to weak, fragile bones (osteoporosis), which raises the risk of fractures.^[1]
• It can also contribute to rickets in children and osteomalacia in adults, though these are more often caused by low vitamin D.^[1]
• Low intake usually causes no symptoms in the short term because the body draws calcium from bones.^[1]

Why symptoms alone cannot confirm a deficiency

Signs like tiredness, weakness, hair fall or low mood are very common and have many possible causes, such as poor sleep, stress, infections, thyroid problems or other illnesses.

The same sign can come from several different nutrients, or from no nutrient problem at all.

Only a qualified clinician, using your history, an examination and, when needed, lab tests, can say whether a deficiency is present. This app cannot diagnose a deficiency from symptoms or from BMI.

Muscle cramps and aches are common and rarely mean low calcium intake. Low blood calcium is usually caused by vitamin D or magnesium problems, or hormone or kidney conditions, not by diet alone.

Tests a clinician might consider

• Blood calcium can be measured, but because the body keeps it tightly controlled, it does not show whether someone eats enough calcium.^[1]
• Bone health is usually assessed by measuring bone mineral density, together with vitamin D status and other risk factors, as the clinician sees fit.^[1]

Who is more likely to have low intake

• Women after menopause, who lose bone faster.^[1]
• People who avoid dairy, including people with lactose intolerance or milk allergy and those following a vegan diet.^[1]

Potential benefits and quality of evidence

• Enough calcium, with enough vitamin D, is needed to build and keep healthy bones.^[1] Established
• Calcium and vitamin D supplements may help bone density in some older adults, but trials disagree on whether they prevent fractures.^[1] Moderate evidence
• Calcium supplements may lower the risk of pre-eclampsia in pregnant women whose calcium intake is low; this must be decided by their obstetric care team.^[1] Moderate evidence
• Whether calcium affects cancer risk, heart disease or weight is unclear.^[1] Not enough evidence

Side effects

• Calcium supplements can cause gas, bloating or constipation. Calcium carbonate seems to cause these more often than calcium citrate.^[1]
• The body absorbs a smaller share of calcium when a large amount is taken at once.^[1]

Risks of too much

• Higher intakes from supplements might raise the risk of kidney stones.^[1]
• Some research suggests calcium supplements could increase cardiovascular risk; other studies find no effect.^[1]
• Very high blood calcium is rare in healthy people and is usually caused by medical conditions, but too much from supplements can contribute.^[1]

Medicine and supplement interactions

• Levothyroxine (thyroid medicine): Calcium carbonate can reduce its absorption; doses are usually separated, as directed on the medicine label or by the doctor.^[1]
• Quinolone antibiotics (e.g., ciprofloxacin): Calcium can reduce absorption of the antibiotic if taken at the same time.^[1]
• Dolutegravir (HIV medicine): Calcium supplements can lower blood levels of the medicine.^[1]
• Lithium: Long-term lithium can raise blood calcium; adding calcium supplements could increase this risk.^[1]
• Vitamin D supplements and thiazide diuretics: Can raise calcium levels further; see the vitamin D article.^[3]

Never start, stop or change a prescribed medicine because of this list — talk to your doctor or pharmacist.

Pregnancy and breastfeeding

• Needs in pregnancy are the same as for other adults in US reference values. Calcium may reduce pre-eclampsia risk in women with low intakes, but use of supplements in pregnancy should follow the obstetric care team’s advice.^[1]

Kidney and liver cautions

• People with kidney disease or a history of kidney stones should talk to their doctor before taking calcium supplements, because supplements might raise kidney-stone risk and kidney disease changes how calcium is handled.^[1]

Upper intake limits

When to talk to a professional

Talk to a doctor or registered dietitian before starting a supplement, especially if you are pregnant or breastfeeding, have a long-term illness, or take any regular medicines.

Do not start, stop or change a prescribed medicine because of anything you read here.

Supplements sold without a prescription are not automatically safe. Doses, quality and interactions still matter.

Seek medical care promptly if you have severe, sudden or worsening symptoms.

Older adults concerned about bone health should discuss calcium, vitamin D and bone checks with their doctor as part of an overall plan.

Still being verified

• ICMR-NIN 2020 values for pregnancy/lactation and Tolerable Upper Limit not verified; not stated.
• Calcium content of ragi to be added from a source we are licensed to use.

References

1. NIH Office of Dietary Supplements. Calcium — Fact Sheet for Health Professionals (opens in a new tab) (2026-06-22). Accessed 9 Oct 2026.
2. ICMR-National Institute of Nutrition (India). A Brief Note on Nutrient Requirements for Indians, the Recommended Dietary Allowances (RDA) and the Estimated Average Requirements (EAR), ICMR-NIN, 2020 (opens in a new tab). Accessed 9 Oct 2026.
3. NIH Office of Dietary Supplements. Vitamin D — Fact Sheet for Health Professionals (opens in a new tab) (2025-06-27). Accessed 9 Oct 2026.
4. USDA Agricultural Research Service, FoodData Central. FoodData Central — SR Legacy (opens in a new tab) (2018-04-01). Accessed 9 Oct 2026.

Sources checked: 9 Oct 2026