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 used for treatment and prevention of low calcium levels and resulting bone conditions including 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 used for premenstrual syndrome (PMS), leg cramps in pregnancy, high blood pressure in pregnancy (pre-eclampsia), and reducing the risk of colon and rectal cancers.
Some people use calcium for complications after intestinal bypass surgery, high blood pressure, high cholesterol, Lyme disease, to reduce high fluoride levels in children, and to reduce high lead levels.
Calcium carbonate is used as an antacid for “heartburn.” Calcium carbonate and calcium acetate are also used for reducing phosphate levels in people with kidney disease.
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?"
Natural Medicines Comprehensive Database 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.
The effectiveness ratings for CALCIUM are as follows:
More evidence is needed to rate the effectiveness of calcium for these uses.
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.
Calcium is LIKELY 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. Some recent research also suggests that doses over the recommended daily requirement of 1000-1300 mg daily for most adults might increase the chance of heart attack. This research is concerning, but it is still too soon to say for certain that calcium is truly the cause 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.
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.
Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.
Calcium can increase how much aluminum your body absorbs when taken with aluminum hydroxide. The increase in aluminum levels might become toxic in people with kidney disease.
Calcium might decrease how much antibiotic your body absorbs. Taking calcium along with some antibiotics known as "quinolones" might decrease their effectiveness. To avoid this interaction, take these drugs at least 2 hours before, or 4 to 6 hours after calcium supplements.
Some quinolone antibiotics that might interact with calcium include ciprofloxacin (Cipro), levofloxacin (Levaquin), ofloxacin (Floxin), moxifloxacin (Avelox), gatifloxacin (Tequin), gemifloxacin (Factive), and others.
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 at least 2 hours before or 4 to 6 hours after taking tetracyclines.
Some tetracyclines include demeclocycline (Declomycin), minocycline (Minocin), and tetracycline (Achromycin, and others).
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, preferably, at a different time of day.
Some bisphosphonates include alendronate (Fosamax), etidronate (Didronel), ibandronate (Boniva), risedronate (Actonel), tiludronate (Skelid), and others.
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.
Interaction Rating = Major Do not take this combination.
Administering intravenous ceftriaxone (Rocephin) 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 (Rocephin).
Calcium can affect your heart. Digoxin (Lanoxin) is used to help your heart beat stronger. Taking calcium along with digoxin (Lanoxin) might increase the effects of digoxin (Lanoxin) and lead to an irregular heartbeat. If you are taking digoxin (Lanoxin), talk to your doctor before taking calcium supplements.
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).
Interaction Rating = Minor Be watchful with this combination.
Talk with your health provider.
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.
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.
Long-term lithium use can increase calcium levels in the blood too much. Taking lithium with calcium supplements might increase this risk even more.
Some medications for high blood pressure can affect calcium in your body. These medications are called calcium channel blockers. Getting calcium injections might decrease the effectiveness of these medications for high blood pressure.
Some medications for high blood pressure include nifedipine (Adalat, Procardia), verapamil (Calan, Isoptin, Verelan), diltiazem (Cardizem), isradipine (DynaCirc), felodipine (Plendil), amlodipine (Norvasc), and others.
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).
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).
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).
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.
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.
Taking prebiotics or probiotics along with calcium might increase the absorption of calcium.
Taking vitamin D along with calcium increases absorption of calcium.
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.
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.
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.
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.
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.
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.
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.
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.
Natural Medicines disclaims any
responsibility related to medical consequences of using any medical
product. Effort is made to ensure that the information contained in this
Natural Medicines monograph is accurate at the time it was published.
However, we cannot guarantee the information is error-free and disclaim
any liability or responsibility for any reliance on it. The information
is also not intended to be a substitute for medical or other
professional advice, and you should not use any product or substances
reference herein without consulting a medical professional. Consumers
and medical professionals who consult this Natural Medicines
monograph are cautioned that any medical or product related decision is
the sole responsibility of the consumer and/or the health care
professional. A legal License Agreement sets limitations on downloading,
storing, or printing content from Natural Medicines. Except for any possible exceptions written into your License Agreement, no reproduction of this monograph or any content from Natural Medicines is permitted without written permission from the publisher. Unlawful to download, store, or distribute content from Natural Medicines or this site.
For the latest comprehensive data on this and every other natural medicine, health professionals should consult the Professional Version of Natural Medicines. It is fully referenced and updated daily.
© Copyright 1995-2015 Therapeutic Research Center, publishers of Natural Medicines, Prescriber's Letter, and Pharmacist's Letter. All rights reserved.
Discover the different ways you can help
1-877 GO KOMEN(1-877-465-6636)