Calcium is a mineral that is an essential part of bones and teeth. The heart, nerves, and blood-clotting systems also need calcium to work.

Calcium is commonly taken by mouth for the treatment and prevention of low calcium levels. It is also used for conditions linked with low calcium levels including muscle cramps (latent tetany), osteoporosis (weak bones due to low bone density), rickets (a condition in children involving softening of the bones), and osteomalacia (a softening of bones involving pain). Calcium is sometimes taken by mouth to reduce high levels of the parathyroid hormone (hyperparathyroidism) and for symptoms of premenstrual syndrome (PMS) along with many other conditions.

Calcium carbonate is taken by mouth as an antacid for "heartburn." Calcium carbonate and calcium acetate are also taken by mouth to reduce phosphate levels in people with kidney disease.

Calcium is also used as a mouth rinse to prevent and reduce pain and swelling inside of the mouth following chemotherapy. Calcium is given intravenously (by IV) for very low calcium levels of the blood and related symptoms. It is also used for high potassium levels in the blood.

Calcium-rich foods include milk and dairy products, kale and broccoli, as well as the calcium-enriched citrus juices, mineral water, canned fish with bones, and soy products processed with calcium.

Calcium can interact with many prescription medications, but sometimes the effects can be minimized by taking calcium at a different time. See the section titled "Are there any interactions with medications?"


Is a Form of:


Primary Functions:

Treatment and Prevention of low calcium levels

Also Known As:

Calcium Acetate, Calcium Aspartate, Calcium Carbonate, Calcium Chelate

How Does It Work?

The bones and teeth contain over 99% of the calcium in the human body. Calcium is also found in the blood, muscles, and other tissue. Calcium in the bones can be used as a reserve that can be released into the body as needed. The concentration of calcium in the body tends to decline as we age because it is released from the body through sweat, skin cells, and waste. In addition, as women age, absorption of calcium tends to decline due to reduced estrogen levels. Calcium absorption can vary depending on race, gender, and age.

Bones are always breaking down and rebuilding, and calcium is needed for this process. Taking extra calcium helps the bones rebuild properly and stay strong.


  • Indigestion (dyspepsia). Taking calcium carbonate by mouth as an antacid is effective for treating indigestion.
  • High levels of potassium in the blood (hyperkalemia). Giving calcium gluconate intravenously (by IV) can reverse heart problems caused by hyperkalemia, a condition in which there is too much potassium in the blood.
  • Low levels of calcium in the blood (hypocalcemia). Taking calcium by mouth is effective for treating and preventing hypocalcemia. Also, giving calcium intravenously (by IV) is effective for treating very low levels of calcium.
  • Kidney failure. Taking calcium carbonate or calcium acetate by mouth is effective for controlling high phosphate levels in the blood in people with kidney failure. Calcium citrate is not effective for treating this condition. Taking calcium by mouth also seems to be helpful for reducing blood pressure in people with kidney failure.
  • Bone loss in people taking drugs called corticosteroids. Taking calcium along with vitamin D seems to reduce the loss of bone mineral in people using corticosteroid drugs long-term.
  • Overactive parathyroid (hyperparathyroidism). Taking calcium by mouth reduces parathyroid hormone levels in people with kidney failure and parathyroid hormone levels that are too high.
  • Weak and brittle bones (osteoporosis). Taking calcium by mouth is effective for preventing bone loss and treating osteoporosis. Most bone growth occurs in the teenage years. After that, bone strength in women remains about the same until age 30-40. After age 40, bone loss typically occurs at rates of 0.5% to 1% per year. In men, this bone loss occurs several decades later. Bone loss is greater in people getting less than the recommended amount of calcium from their diet. This is very common among Americans. Bone loss in women over 40 can be reduced by taking calcium supplements. Some researchers estimate that taking calcium for 30 years after menopause might result in a 10% improvement in bone strength. Taking calcium alone or with vitamin D also helps prevent fractures in people with osteoporosis.
  • Premenstrual syndrome (PMS). There seems to be a link between low dietary calcium intake and symptoms of PMS. Consuming calcium daily seems to significantly reduce mood swings, bloating, food cravings, and pain. Also, increasing the amount of calcium in one's diet seems to prevent PMS. Women consuming an average of 1283 mg/day of calcium from foods seem to have about a 30% lower risk of PMS than women who consume an average of 529 mg/day of calcium.
  • Colon cancer, rectal cancer. Research suggests that high intake of calcium in the diet or as a supplement reduces the risk of colorectal cancer. But not all research agrees. People with low levels of vitamin D do not seem to benefit from calcium supplements. People who are overweight or obese also seem to be less likely to benefit from calcium supplements.
  • Increasing bone strength in the unborn baby. In pregnant women who eat a low amount of calcium as part of their diet, calcium supplementation increases the bone mineral density of the fetus. However, this does not appear to be beneficial for women with normal calcium levels.
  • A condition caused by ingestion of too much fluoride (fluorosis). Taking calcium by mouth, together with vitamin C and vitamin D supplements, seems to reduce fluoride levels in children and improve symptoms of fluoride poisoning.
  • High cholesterol. Taking calcium supplements along with a low-fat or low-calorie diet seems to modestly reduce low-density lipoprotein (LDL) or "bad" cholesterol and modestly increase high-density lipoprotein (HDL) or "good" cholesterol. Taking calcium alone, without the restricted diet, does not seem to lower cholesterol.
  • High blood pressure. Taking calcium supplements seems to reduce blood pressure by a small amount (usually around 1-2 mmHg) in people with or without high blood pressure. Calcium seems to work best in salt-sensitive people and people who normally get very little calcium. Some research also suggests that taking calcium might reduce the risk of having high blood pressure.
  • A pregnancy complication marked by high blood pressure and protein in the urine (pre-eclampsia). Taking 1-2 grams of calcium by mouth daily seems to reduce the risk of pregnancy-related high blood pressure. Calcium appears to have the greatest effect in high-risk women, in women with low calcium levels, and when started by the 20th week of pregnancy.
  • Softening of bones in children, often due to vitamin D deficiency (rickets). Rickets is mostly commonly due to vitamin D deficiency, but very low calcium intake can also cause rickets.
  • Preventing tooth loss (tooth retention). Taking calcium and vitamin D by mouth appears to help prevent tooth loss in older people.

Recommended Dosing

The following doses have been studied in scientific research:


  • For preventing low calcium levels: 1-2 grams elemental calcium daily is typically used. Sometimes it is taken with 800 IU of vitamin D.
  • For heartburn: 0.5-1.5 grams of calcium carbonate is used as needed.
  • To reduce phosphates in adults with chronic renal failure: 1-6.5 grams per day of calcium carbonate or calcium acetate has been used. The daily dose is divided up and taken between meals.
  • For preventing weak bones (osteoporosis) caused by corticosteroid use: Divided daily doses of 0.5-1 gram of elemental calcium daily.
  • For reducing parathyroid hormone levels (hyperparathyroidism): 1.2-4 grams of calcium, usually as a carbonate salt. Often it is used in combination with a low-phosphate diet or 800 IU of vitamin D.
  • For prevention of weak bones (osteoporosis): Most experts recommend taking 1000-1200 mg of calcium daily to prevent osteoporosis and broken bones.
  • For increasing fetal bone density in pregnant women with low dietary calcium intake: 300-2000 mg/day, taken during the second and third trimesters.
  • For premenstrual syndrome (PMS): 1-1.3 grams per day as calcium carbonate.
  • For preventing colorectal cancer and recurrent colorectal benign tumors (adenomas): Up to 2 grams daily.
  • For high cholesterol: 800 mg daily for up to 2 years. Calcium 1200 mg taken in 2-3 divided doses daily, alone or in combination with vitamin D 400 IU daily, has also been used in conjunction with a low-fat or calorie-restricted diet for up to 15 weeks.
  • For preventing high blood pressure during pregnancy (pre-eclampsia): 1-2 grams elemental calcium daily as calcium carbonate.
  • For high blood pressure: Up to 0.4-2 grams daily for up to 4 years
  • For preventing tooth loss in elderly people: 500 mg of calcium along with 700 IU of vitamin D daily for 3 years.
  • For weight loss: Calcium 800-1200 mg daily with or without a calorie-restricted diet has been used. In some cases, calcium is taken in combination with 400 IU of vitamin D.


  • For low calcium levels in the blood: 100-200 mg of calcium is given as a bolus dose
  • For high potassium levels in the blood: 20 mL of 10% calcium gluconate is administered over 5-10 minutes in most adults. In adults taking digoxin, the dose is administered over 20-30 minutes.



  • For preventing fluoride poisoning: Calcium 125 mg twice daily, in combination with ascorbic acid and vitamin D.
  • High blood pressure: 1.5 grams per day for 8 weeks has been used in adolescents.


  • For high potassium levels in the blood: 0.5 mL of 10% calcium gluconate is administered over 5-10 minutes.

Calcium carbonate and calcium citrate are the two most commonly used forms of calcium.

Calcium supplements are usually divided into two doses daily in order to increase absorption. It's best to take calcium with food in doses of 500 mg or less.

The Institute of Medicine publishes a recommended daily allowance (RDA) for calcium which is an estimate of the intake level necessary to meet the requirements of nearly all healthy individuals in the population. The current RDA was set in 2010. The RDA varies based on age as follows: Age 1-3 years, 700 mg; 4-8 years, 1000 mg; 9-18 years, 1300 mg; 19-50 years, 1000 mg; Men 51-70 years, 1000 mg; Women 51-70 years, 1200 mg; 70+ years, 1200 mg; Pregnant or Lactating (under 19 years), 1300 mg; Pregnant or Lactating (19-50 years), 1000 mg.

The Institute of Medicine also sets the daily tolerable upper intake level (UL) for calcium based on age as follows: Age 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-3 years, 2500 mg; 9-18 years, 3000 mg; 19-50 years, 2500 mg; 51+ years, 2000 mg. Doses above these levels should be avoided.

Doses over the recommended daily intake level of 1000-1300 mg/day for most adults have been associated with an increased risk of heart attack. Until more is known, continue consuming adequate amounts of calcium to meet daily requirements, but not excessive amounts of calcium. Be sure to consider total calcium intake from both dietary and supplemental sources and try not to exceed 1000-1300 mg of calcium per day. To figure out dietary calcium, count 300 mg/day from non-dairy foods plus 300 mg/cup of milk or fortified orange juice.

Calcium Supplements Frequently Asked Questions

What is the best form of calcium to take?

Calcium carbonate and calcium citrate are the optimal forms of supplement. Calcium carbonate should be taken with meals because it requires stomach acid to dissolve and absorb. Calcium carbonate has the most calcium per pill (40 percent), therefore fewer pills are needed.

Can calcium supplements be harmful?

“The truth is, the research is inconclusive. But there is a growing body of evidence that suggests no health benefit, or even worse, that calcium supplements may be harmful.” Multiple studies have found that there's little to no benefit to taking calcium supplements for the prevention of hip fractures.

Can I take calcium tablet daily?

In general, it's best to take calcium supplements with food. For better absorption, don't take more than 500 milligrams at one time. Split up larger doses over the course of the day. For the body to make use of calcium properly, you also need to get enough vitamin D and magnesium.

When should you take calcium supplements?

To maximize your absorption of calcium, take no more than 500 mg at a time. You might take one 500 mg supplement in the morning and another at night. If you take a supplement that also contains vitamin D, it will help your body absorb calcium more efficiently.

What are the side effects of taking calcium with vitamin D?

  • an irregular heartbeat
  • nausea, vomiting, or decreased appetite
  • dry mouth
  • constipation
  • weakness
  • headache
  • a metallic taste
  • muscle or bone pain

What are the side effects of calcium tablets?

Side effects.

At normal doses, calcium supplements may cause bloating, gas, and constipation. Very high doses of calcium can cause kidney stones.

Who should not take calcium supplements?

33 For healthy children, there has been no recommendation for routine calcium supplementation. In clinical practice, children with a high risk of osteoporosis (eg, celiac disease, inflammatory bowel disease, or congenital bone disorder) or low calcium intake may benefit from calcium supplementation.

How much calcium should a 60 year old woman take daily?

The National Osteoporosis Foundation recommends that women aged 50 or younger and men 70 or younger should get 1,000 milligrams (mg) of calcium per day. Men and women older than that should get 1,200 mg daily.

What is the safest calcium supplement to take?

Calcium citrate supplements are absorbed more easily than calcium carbonate. They can be taken on an empty stomach and are more readily absorbed by people who take acid-reducing heartburn medications. But because calcium citrate is only 21% calcium, you may need to take more tablets to get your daily requirement.

What are the symptoms of lack of calcium?

  • confusion or memory loss.
  • muscle
  • numbness and tingling in the hands, feet, and face.
  • muscle
  • weak and brittle nails.
  • easy fracturing of the bones.

Does calcium tablets increase weight?

Data suggest that a diet deficient in calcium is associated with higher body weight and that augmenting calcium intake may reduce weight and fat gain or enhance loss. Calcium supplementation did not significantly affect amount of weight or fat lost by women counseled to follow a moderately restricted diet for 25 wk.

What are the symptoms of calcium deficiency in adults?

Signs and Symptoms of Calcium Deficiency

  • Tingling Fingers.
  • Muscle
  • Poor appetite.
  • Weak or brittle fingernails.
  • Difficulty swallowing.

Does taking calcium at night help you sleep?

William Sears, M.D. writes: "Calcium helps the brain use the amino acid tryptophan to manufacture the sleep-inducing substance melatonin. This explains why dairy products, which contain both tryptophan and calcium, are one of the top sleep-inducing foods."

Can you take vitamin D and calcium together?

While your body needs vitamin D to absorb calcium, you do not need to take vitamin D at the same time as a calcium supplement.

What is the best form of calcium to take for osteoporosis?

The two most commonly used calcium products are calcium carbonate and calcium citrate. Calcium carbonate supplements dissolve better in an acid environment, so they should be taken with a meal. Calcium citrate supplements can be taken any time because they do not need acid to dissolve.

Why you shouldn't take calcium supplements?

On the other hand, recent studies have linked calcium supplements with an increased risk of colon polyps (small growths in the large intestine that can become cancerous) and kidney stones, which are hard masses usually formed in the kidneys from an accumulation of calcium and other substances.

When should you take calcium tablets morning or night?

To maximize your absorption of calcium, take no more than 500 mg at a time. You might take one 500 mg supplement in the morning and another at night. If you take a supplement that also contains vitamin D, it will help your body absorb calcium more efficiently.

Is taking calcium bad for the heart?

After analyzing 10 years of medical tests on more than 2,700 people in a federally funded heart disease study, researchers at Johns Hopkins Medicine and elsewhere conclude that taking calcium in the form of supplements may raise the risk of plaque buildup in arteries and heart damage, although a diet high in calcium

What is the best calcium supplement for seniors?

The Right Calcium Supplement for Senior Citizens

  • Calcium This form of calciumis considered easy to absorb.
  • Calcium Rolaids and TUMS both contain calciumcarbonate.
  • Calciumwith Vitamin D.
  • The Best Calcium Supplementfor You.
  • CalciumQuality, Purity and Potency.
  • Calcium
  • Calciumand Other Medications.

How do you increase calcium in old age?

Calcium Intake for Adults over Age 55

  • Dairy products, such as cheese, milk and yogurt.
  • Dark green leafy vegetables, such as broccoli and kale.
  • Fish with edible soft bones, such as sardines and canned salmon.
  • Calcium-fortified foods and beverages, such as soy products, cereal and fruit juices, and milk substitutes.

Clinical Studies