How can I take calcium supplements effectively?

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Calcium won’t just protect your bones, it’s also an important way to keep your muscles strong. Pair 600 mg calcium with 400 mg magnesium to help with absorption. Additionally, be sure to take it two hours after eating or taking your multivitamin, as calcium can block the body from absorbing other nutrients.

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If you take calcium supplements, take them with vitamin D (they're often combined in one pill) to help absorption -- and with a little magnesium to reduce the constipation sometimes caused by calcium. Don't pair calcium with iron or fiber supplements, which can interfere with your body's ability to absorb the bone-building mineral.
Your body can most effectively absorb calcium if you take it in doses of 500 milligrams (mg) or less a few times during the day. Also, you may absorb more calcium from a chewable or liquid supplement than from a pill, because a pill may not dissolve easily in the stomach.

Calcium carbonate, a form of calcium often found in over-the-counter chewable antacid pills, is best taken with low-iron meals, such as breakfast. Calcium citrate, another form available in supplements, can be taken on either an empty or full stomach.

Talk with your pharmacist or doctor about your other prescription and over-the-counter medicines to make sure they are not reducing the effectiveness of your calcium supplement. You may need to adjust your medicines or supplements to make sure you’re getting enough calcium. And taking a vitamin D supplement can help increase the absorption of calcium.
Dr. Vonda Wright, MD
Orthopedic Surgery
Calcium supplements come in two varieties -- calcium carbonate, and calcium citrate. Bones don't care which kind you take, just as long as you do. They must be taken differently, however. Calcium carbonate should be taken with meals because they need stomach acid to absorb. Calcium citrate doesn't need to be taken with food. In general, you absorb more calcium when these supplements are taken with food and when no more than 500 mg are taken at one time. Most of these supplements also come in formulas that include a dose of vitamin D. If you get the combination form, you'll get both nutrients in one pill.
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If you choose to take a calcium supplement, opt for calcium citrate, which has been found to dissolve easier than calcium carbonate or calcium phosphate and can be taken with or without food. It also produces no gas or constipation. For the best absorption, take calcium supplements as follows:
  • Space them throughout the day; avoid ingesting more than 500 mg at once.
  • Take them with food, whether a meal or snack, but not with high-fat foods. A large amount of fat can block calcium’s release into the body.
  • Do not take them with foods high in fiber, such as whole grain cereals or bulk-forming laxatives, which also interfere with absorption.  
  • Do not take them with iron. Calcium can bind with iron, limiting the amount of either nutrient the body receives, so if you take iron supplements as well as calcium supplements, take them at different times of day.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.