Osteoporosis

How do I know what kind of calcium supplement to take?

There are many types of calcium supplements on the shelves today.

Calcium carbonate (found in Tums, Sodium-Free Rolaids which also has Magnesium hydroxide, Caltrate 600, Cal-Plus, and many generics) is currently the preferred and least expensive form of calcium supplement.
Citrical, or calcium citrate, may be better absorbed in those who lack gastric acid, but it is also more expensive. Calcium citrate or calcium lactate are probably better choices for people over 65 or people with ulcers.
All are equally effective when taken properly.
Avoid supplements sold as "natural sources" of calcium, such as coral calcium, dolomite, bone meal, or oyster shell, especially if your are pregnant. They can be contaminated with hazardous amounts of toxic heavy metals like arsenic and lead. There is no evidence that these products are more effective.
Take a calcium carbonate supplement (whether Tums or something else) with a meal to make sure the acid level of the stomach is all right.
An adequate vitamin D level is required by the body to absorb calcium. The recommended amount of vitamin D for adults is 400 IU/day. For women over 70, the recommended daily amount is 600 IU.
Do not take a vitamin with iron, or an iron supplement, at the same time as your calcium supplement. The two compete for the same binding site in your body,and will reduce absorption. This same logic applies to taking an iron supplement with a glass of milk, since milk is high in calcium.
Another way to determine which supplement to take is to figure out how much calcium you are getting from your regular diet and then choose a supplement that will raise that level to the recommended daily calcium intake.
You should not take your entire amount of calcium all at once. For instance, you should not take 2 calcium tablets at the same time, or take several Tums with a tall glass of milk. Spread out the doses to improve absorption-probably no more than 500 mg at a time.
If you have a history of kidney stones, you should definitely talk to your doctor before taking a supplement. Taking supplements is not risk-free.
The best advice is to get as much calcium as possible from your diet, supplement as needed, and exercise.

The development of this topic was funded in part by the Ohio Department of Health.

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Last Reviewed: Apr 14, 2006

Margery Gass, MD
Professor, Clinical Obstetrics & Gynecology
Department of Obstetrics & Gynecology
College of Medicine
University of Cincinnati

Thomas A deHoop, MD
Associate Professor of Clinical Obstetrics and Gynecology
Director, Medical Student Education
Department of Obstetrics & Gynecology
College of Medicine
University of Cincinnati

Jane Korsberg, MS, RD, LD
Senior Instructor
Department of Nutrition
School of Medicine
Case Western Reserve University