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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-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 is also taken as a supplement.

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, weak and brittle bones (osteoporosis), softening of bones in children, often due to vitamin D deficiency (rickets), and softening of the bones (osteomalacia). Calcium is sometimes taken by mouth to reduce high levels of the parathyroid hormone in people with an overactive parathyroid (hyperparathyroidism) and for symptoms of premenstrual syndrome (PMS), along with many other conditions.

Calcium carbonate is taken by mouth as an antacid for indigestion (dyspepsia). Calcium carbonate and calcium acetate are also taken by mouth to reduce phosphate levels in people with kidney failure.

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
  • Dyspepsia.  Oral calcium carbonate is approved by the US Food and Drug Administration (FDA) as an antacid.
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  • Hyperkalemia.  Intravenous calcium gluconate is approved by the US Food and Drug Administration (FDA) for preventing hyperkalemia-induced cardiac abnormalities.
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  • Hypocalcemia.  Oral calcium treats and prevents hypocalcemia. Intravenous calcium is used to treat severe hypocalcemia.
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  • Kidney failure.  Oral calcium carbonate or calcium acetate is used as a phosphate binder during kidney failure.
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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.

When taken by mouth: Calcium is LIKELY SAFE for most people when taken by mouth and in recommended amounts (about 1000-1200 mg daily). Calcium can cause some minor side effects such as belching or gas. But calcium is POSSIBLY UNSAFE when taken by mouth in doses above the daily tolerable upper intake level (UL). The UL is 2000 mg for adults ages 19-50 years and 2000 mg for adults over 50 years. Taking more than this amount of calcium daily can increase the chance of having serious side effects, such as 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, but not all research agrees.

When given by IV: Calcium is LIKELY SAFE for most people when given intravenously (by IV) and appropriately.

Special Precautions & Warnings:

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. Calcium is POSSIBLY UNSAFE when taken during pregnancy by mouth in doses above the daily tolerable upper intake level (UL). The UL is 3000 mg under 18 years of age and 2500 mg for over 18 years of age. Higher doses might increase the risk of seizures in the infant. Be sure to consider total calcium intake from both dietary and supplemental sources of calcium. This includes over-the-counter antacids. Try not to take more than 1000-1200 mg of calcium from supplements per day unless prescribed by your doctor. Some women may be prescribed calcium to prevent high blood pressure during pregnancy.

Children: Calcium is LIKELY SAFE for most children when taken by mouth in recommended amounts. The recommended amount varies based on age as follows: Age 1-3 years, 700 mg daily; 4-8 years, 1000 mg daily; 9-18 years, 1300 mg daily. But calcium is POSSIBLY UNSAFE when taken by mouth in higher doses. Taking more than the recommended amount of calcium daily can increase the chance of having serious side effects. Children should be advised to continue consuming adequate amounts of calcium to meet daily requirements, but not excessive amounts of calcium.

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.

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.

Antibiotics (Quinolone antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

Calcium might decrease how much antibiotic your body absorbs. Taking calcium along with some antibiotics might decrease the effectiveness of some antibiotics. To avoid this interaction, take calcium supplements at least 1 hour after antibiotics.

Some of these antibiotics that might interact with calcium include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), and trovafloxacin (Trovan).

Antibiotics (Tetracycline antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

Calcium can attach to some antibiotics called tetracyclines in the stomach. This decreases the amount of tetracyclines that can be absorbed. Taking calcium with tetracyclines might decrease the effectiveness of tetracyclines. To avoid this interaction take calcium 2 hours before or 4 hours after taking tetracyclines.

Some tetracyclines include demeclocycline (Declomycin), minocycline (Minocin), and tetracycline (Achromycin, and others).

Bisphosphonates

Interaction Rating=Moderate Be cautious with this combination.

Calcium can decrease how much bisphosphate your body absorbs. Taking calcium along with bisphosphates can decrease the effectiveness of bisphosphate. To avoid this interaction, take bisphosphonate at least 30 minutes before calcium or later in the day.

Some bisphosphonates include alendronate (Fosamax), etidronate (Didronel), risedronate (Actonel), tiludronate (Skelid), and others.

Calcipotriene (Dovonex)

Interaction Rating=Moderate Be cautious with this combination.

Calcipotriene (Dovonex) is a drug that is similar to vitamin D. Vitamin D helps your body absorb calcium. Taking calcium supplements along with calcipotriene (Dovonex) might cause the body to have too much calcium.

Calcium channel blockers

Interaction Rating=Minor Be watchful with this combination.

Calcium when given intravenously may decrease the effects of calcium channel blockers. It is used in the management of calcium channel blocker overdose. Intravenous calcium gluconate has been used before intravenous verapamil (Isoptin) to prevent or reduce the hypotensive effects without affecting the antiarrhythmic effects (6124). But there is no evidence that dietary or supplemental calcium when taken orally interacts with calcium channel blockers (12939,12947). The calcium channel blockers include nifedipine (Adalat, Procardia), verapamil (Calan, Isoptin, Verelan), diltiazem (Cardizem), isradipine (DynaCirc), felodipine (Plendil), amlodipine (Norvasc), and others.

Ceftriaxone (Rocephin)

Interaction Rating=Major Do not take this combination.

Administering intravenous ceftriaxone and calcium can result in life-threatening damage to the lungs and kidneys. Calcium should not be administered intravenously within 48 hours of intravenous ceftriaxone.

Digoxin (Lanoxin)

Interaction Rating=Moderate Be cautious with this combination.

Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin (12940). However, one retrospective analysis of clinical data suggests that intravenous calcium does not increase the risk of dysrhythmias or mortality in patients receiving digoxin (38960). To be cautious, avoid administering intravenous calcium to patients taking digoxin.

Diltiazem (Cardizem, Dilacor, Tiazac)

Interaction Rating=Moderate Be cautious with this combination.

Calcium can affect your heart. Diltiazem (Cardizem, Dilacor, Tiazac) can also affect your heart. Taking large amounts of calcium along with diltiazem (Cardizem, Dilacor, Tiazac) might decrease the effectiveness of diltiazem (Cardizem, Dilacor, Tiazac).

Estrogens

Interaction Rating=Minor Be watchful with this combination.

Estrogen helps your body absorb calcium. Taking estrogen pills along with large amounts of calcium might increase calcium in the body too much.

Estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.

LITHIUM

Interaction Rating=Moderate Be cautious with this combination.

Clinical evidence suggests that long-term use of lithium may cause hypercalcemia in 10% to 60% of patients (38953). Theoretically, concomitant use of lithium and calcium supplements may further increase this risk.

Levothyroxine

Interaction Rating=Moderate Be cautious with this combination.

Levothyroxine is used for low thyroid function. Calcium can decrease how much levothyroxine your body absorbs. Taking calcium along with levothyroxine might decrease the effectiveness of levothyroxine. Levothyroxine and calcium should be taken at least 4 hours apart.

Some brands that contain levothyroxine include Armour Thyroid, Eltroxin, Estre, Euthyrox, Levo-T, Levothroid, Levoxyl, Synthroid, Unithroid, and others.

Sotalol (Betapace)

Interaction Rating=Moderate Be cautious with this combination.

Taking calcium with sotalol (Betapace) can decrease how much sotalol (Betapace) your body absorbs. Taking calcium along with sotalol (Betapace) might decrease the effectiveness of sotalol (Betapace). To avoid this interaction, take calcium at least 2 hours before or 4 hours after taking sotalol (Betapace).

Verapamil (Calan, Covera, Isoptin, Verelan)

Interaction Rating=Moderate Be cautious with this combination.

Calcium can affect your heart. Verapamil (Calan, Covera, Isoptin, Verelan) can also affect your heart. Do not take large amounts of calcium if you are taking verapamil (Calan, Covera, Isoptin, Verelan).

Water pills (Thiazide diuretics)

Interaction Rating=Moderate Be cautious with this combination.

Some "water pills" increase the amount of calcium in your body. Taking large amounts of calcium with some "water pills" might cause there to be too much calcium in the body. This could cause serious side effects, including kidney problems.

Some of these "water pills" include chlorothiazide (Diuril), hydrochlorothiazide (HydroDIURIL, Esidrix), indapamide (Lozol), metolazone (Zaroxolyn), and chlorthalidone (Hygroton).

Iron: Calcium supplements can decrease the absorption of dietary iron. In people who have enough iron stored in their bodies, taking calcium does not cause a problem over the long term. However, people at high risk for iron deficiency should take calcium supplements at bedtime, instead of with meals, to avoid reducing dietary iron absorption.
Lycopene: Taking calcium together with lycopene may decrease the amount of lycopene that is absorbed from the gut. To avoid this interaction, people should take calcium supplements at bedtime instead of with meals.
Magnesium: Calcium supplements can decrease the absorption of dietary magnesium, but only at very high doses (2600 mg per day). However, in people who have enough magnesium stored in their bodies, taking calcium does not cause a problem over the long term. People at high risk for magnesium deficiency, however, should take calcium supplements at bedtime, instead of with meals, to avoid reducing dietary magnesium absorption.
Vitamin D: Taking vitamin D along with calcium increases absorption of calcium. This might increase the risk of calcium levels becoming too high in some people.
Zinc: Calcium supplements can decrease the absorption of dietary zinc. In people who have enough zinc stored in their bodies, taking calcium does not cause a problem over the long term.

Caffeine-containing foods: High caffeine intake from foods and beverages causes the body to remove calcium. Taking more than 300 mg of caffeine per day (three to four cups of coffee, or six 12-oz. cola drinks) is linked to increased bone loss and breaks in elderly women, especially when calcium intake is low. Be sure to get the amount of calcium from food and supplements that is recommended for your age and gender.
Fiber-containing foods: Dietary fiber from certain sources can interfere with calcium absorption. These sources include wheat bran, spinach, rhubarb, and others. It's best not to eat fibrous foods within two hours of taking calcium supplements.
Iron-containing foods: Calcium supplements may decrease the absorption of dietary iron. However, in people who have enough iron stored in their body, taking calcium does not cause a problem over the long term. People who are at high risk for iron deficiency should take calcium supplements at bedtime, instead of with meals, to avoid reducing the absorption of iron.
Magnesium-containing foods: Calcium supplements may decrease the absorption of dietary magnesium. However, in people who have enough magnesium stored in their body, taking calcium does not cause a problem over the long term. People who are at high risk for magnesium deficiency should take calcium supplements at bedtime, instead of with meals, to avoid reducing the absorption of magnesium.
Protein-containing foods: Eating high-protein diets, particularly from animal sources, might increase how much calcium is excreted in the urine. Eating a low-protein diet might reduce how much calcium is absorbed in the stomach.
Salt-containing foods: Eating foods that contain a lot of sodium causes the body to remove calcium. A calcium intake of 1000 mg/day is needed to prevent bone loss in postmenopausal women ingesting 2000 mg sodium chloride daily. About 1500 mg/day calcium is needed if sodium chloride intake is 3000 mg/day.
Zinc-containing foods: Calcium supplements may decrease the absorption of dietary zinc. However, in people who have enough zinc stored in their body, taking calcium does not cause a problem over the long term. People who are at high risk for zinc deficiency should take calcium supplements at bedtime, instead of with meals, to avoid reducing the absorption of zinc.

The following doses have been studied in scientific research:

BY MOUTH:

  • For preventing low levels of calcium in the blood (hypocalcemia): 1-2 grams elemental calcium daily is typically used. Sometimes it is taken with 800 IU of vitamin D.
  • For indigestion (dyspepsia): 0.5-1.5 grams of calcium carbonate is used as needed.
  • To reduce phosphates in adults with kidney 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 bone loss in people taking drugs called corticosteroids: Divided daily doses of 0.5-1 gram of elemental calcium daily.
  • For reducing parathyroid hormone levels in people with an overactive parathyroid (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 weak and brittle bones (osteoporosis): Most experts recommend taking 1000-1200 mg of calcium daily to prevent osteoporosis and broken bones.
  • For increasing bone strength in the unborn baby: 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 colon cancer, rectal cancer: Up to 2 grams daily.
  • For preventing a pregnancy complication marked by high blood pressure and protein in the urine (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 (tooth retention): 500 mg of calcium along with 700 IU of vitamin D daily for 3 years.
INTRAVENOUS (BY IV):
  • For low levels of calcium in the blood (hypocalcemia): 100-200 mg of calcium is given as a bolus dose
  • For high levels of potassium in the blood (hyperkalemia): 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.
CHILDREN

BY MOUTH
  • For high blood pressure: 1.5 grams per day for 8 weeks has been used in adolescents.
INTRAVENOUS
  • For levels of potassium in the blood (hyperkalemia): 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.

Acétate de Calcium, Aspartate de Calcium, Bone Meal, Calcio, Calcium Acetate, Calcium Aspartate, Calcium Carbonate, Calcium Chelate, Calcium Chloride, Calcium Citrate, Calcium Citrate Malate, Calcium D-Gluconate, Calcium Disuccinate, Calcium Gluconate, Calcium Glycerophosphate, Calcium Hydrogen Phosphate, Calcium Hydroxyapatite, Calcium Lactate, Calcium Lactogluconate, Calcium Orotate, Calcium Phosphate, Calcium Sulfate, Carbonate de Calcium, Chélate de Calcium, Chlorure de Calcium, Citrate de Calcium, Citrate Malate de Calcium, Coquilles d'Huîtres Moulues, Coquilles d'œuf, Dicalcium Phosphate, Di-Calcium Phosphate, Dolomite, Egg Shell Calcium, Gluconate de Calcium, Glycérophosphate de Calcium, Heated Oyster Shell-Seaweed Calcium, Hydroxyapatite, Lactate de Calcium, Lactogluconate de Calcium, MCHA, MCHC, Microcrystalline Hydroxyapatite, Orotate de Calcium, Ossein Hydroxyapatite, Oyster Shell, Oyster Shell Calcium, Phosphate de Calcium, Phosphate de Calcium Hydrogène, Phosphate de di-Calcium, Phosphate Tricalcium, Poudre d'os, Sulfate de Calcium, Tricalcium Phosphate.

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