Calcium

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 taken by mouth for treatment and prevention of low calcium levels and resulting bone conditions 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 also taken by mouth to prevent falls and to prevent high levels of the parathyroid hormone (hyperparathyroidism). It is also taken by mouth for premenstrual syndrome (PMS), leg cramps and depression in pregnancy, high blood pressure in pregnancy (pre-eclampsia), and to improve bone development in the baby. Calcium is used to reduce the risk of cancer, stroke, and cardiovascular disease, to increase survival following a heart attack, to help retain teeth in the elderly, and to help with weight loss.

Some people take calcium by mouth to prevent diarrhea and seizures due to sudden decreases in calcium levels. It is also taken by mouth to prevent for complications after intestinal bypass surgery, high blood pressure, high cholesterol, diabetes, metabolic syndrome, Lyme disease, to reduce high fluoride levels in children, and to reduce high lead levels. Calcium is used to prevent vitamin B12 deficiency associated with the medication metformin. It is also used to increase survival in people who have had a heart attack.

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 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, muscle cramps following spider bites, and during CPR (cardiopulmonary resuscitation). Calcium gluconate and gluceptate may be injected as a shot if calcium cannot be given by IV. 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?"

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.
High levels of potassium in the blood (hyperkalemia).
Low levels of calcium in the blood (hypocalcemia).
Kidney failure.
Weakened bones (osteoporosis)
Parathyroid gland disorder (hyperparathyroidism).
Osteoporosis.
Reducing symptoms of premenstrual syndrome (PMS).
Fluoride poisoning.
High cholesterol.
High blood pressure.
High blood pressure during pregnancy (pre-eclampsia).
Tooth loss.
Weight loss.

Adults

By Mouth:

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/day.

For high cholesterol: 1200 mg daily, alone or in combination with vitamin D, has been used in conjunction with a low-fat or calorie-restricted diet.

For preventing high blood pressure during pregnancy (pre-eclampsia): 1-2 grams elemental calcium daily as calcium carbonate.

For preventing colorectal cancer and recurrent colorectal benign tumors (adenomas): Calcium 1200-1600 mg/day.

For high cholesterol: 1200 mg daily with or without vitamin D 400 IU daily has been used in conjunction with a low-fat or calorie-restricted diet.

For high blood pressure: Up to 0.4-2 grams daily for up to 4 years.

For preventing high blood pressure during pregnancy (pre-eclampsia): 1-2 grams elemental calcium daily as calcium carbonate.

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/day usually in combination with a calorie-restricted diet has been used. In some cases calcium is taken in combination with 400 IU of vitamin D.

Children

By Mouth:

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.

Calcium is SAFE for most people when taken by mouth or when given intravenously (by IV) and appropriately. Calcium can cause some minor side effects such as belching or gas.

Calcium is POSSIBLY UNSAFE for both adults and children when taken by mouth in high doses. Avoid taking too much calcium.

The Institute of Medicine 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; 1-8 years, 2500 mg; 9-18 years, 3000 mg; 19-50 years, 2500 mg; 51+ years, 2000 mg. Higher doses increase the chance of having serious side effects, such as blood levels of calcium that are too high and milk-alkali syndrome, a condition that can lead to renal stones, kidney failure and death.

There is also concern that supplemental calcium can increase the risk of heart attack. Some research shows that taking calcium, often in amounts over the recommended daily intake level of 1000-1300 mg per day, is linked with an increased risk of heart attack in older people.

But other research suggests there is no connection between calcium supplementation and heart attack risk. It may be that some groups have an increased risk while others do not.

Continue consuming adequate amounts of calcium to meet daily requirements, but avoid excessive amounts of calcium. Be sure to consider total calcium intake from both dietary and supplemental sources and try not to exceed 1000-1200 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. Also, if calcium supplements need to be taken along with dietary calcium, consider taking ones that provide calcium along with vitamin D.

Pregnancy and breast-feeding: Calcium is LIKELY SAFE when taken by mouth in recommended amounts during pregnancy and breast-feeding. There is not enough information available on the safety of using calcium intravenously (by IV) during pregnancy and breastfeeding.

Low acid levels in the stomach (achlorhydria). People with low levels of gastric acid absorb less calcium if calcium is taken on an empty stomach. However, low acid levels in the stomach do not appear to reduce calcium absorption if calcium is taken with food. Advise people with achlorhydria to take calcium supplements with meals.

High levels of phosphate in the blood (hyperphosphatemia) or low levels of phosphate in the blood (hypophosphatemia): Calcium and phosphate have to be in balance in the body. Taking too much calcium can throw this balance off and cause harm. Don't take extra calcium without your health provider's supervision.

Under-active thyroid (hypothyroidism): Calcium can interfere with thyroid hormone replacement treatment. Separate calcium and thyroid medications by at least 4 hours.

Too much calcium in the blood (as in parathyroid gland disorders and sarcoidosis): Calcium should be avoided if you have one of these conditions.

Poor kidney function: Calcium supplementation can increase the risk of having too much calcium in the blood in people with poor kidney function.

Smoking: People who smoke absorb less calcium from the stomach.

Stroke: Early research suggests that older women who have had a stroke, taking calcium supplements for 5 or more years might increase the chance of developing dementia. More research is needed to determine if calcium supplements should be avoided for those who have had a stroke.