Northside Health Library

Calcium supplements


Who should take calcium supplements?

Calcium is one of the most important minerals for the human body. Calcium helps form and maintain healthy teeth and bones. Proper levels of calcium over a lifetime can help prevent osteoporosis.

Most people get enough calcium in their everyday diet by eating dairy foods and leafy green vegetables. Older women and men may need extra calcium to prevent their bones from becoming thin (osteoporosis).

Your health care provider will tell you if you need to take extra calcium supplements.

Types of calcium supplements

The two main forms of calcium dietary supplements are calcium carbonate and calcium citrate. Calcium phosphate is less common.

  • Calcium carbonate: Over-the-counter antacid products, such as Tums and Rolaids contain calcium carbonate. These sources of calcium carbonate do not cost very much. Each pill or chew provides 200 - 400 mg of calcium.
  • Calcium citrate: This is a more expensive form of the supplement. It is absorbed well on an empty or full stomach. People with low levels of stomach acid (a condition that is more common in people over age 50) absorb calcium citrate more easily than calcium carbonate.

When choosing a calcium supplement:

  • Look for labels that contain the word "purified" or the United States Pharmacopeia (USP) symbol.
  • Watch out for supplements made from unrefined oyster shell, bone meal, or dolomite that don't have the USP symbol. They may have high levels of lead or other toxic metals.

How to take extra calcium

It is important to increase the dose of your calcium supplement slowly. Take just 500 mg a day for a week, and then slowly add more calcium.

Try to spread the extra calcium throughout the day. Do not take more than 500 mg at a time. Taking calcium throughout the day will:

  • Allow more calcium to be absorbed
  • Decrease side effects such as gas, bloating, and constipation

The total amount of calcium adults need every day from food or calcium supplements:

  • 19 - 50 years: 1,000 mg/day
  • 51 - 70 years:
    • Men - 1,000 mg/day
    • Women - 1,200 mg/day
  • 71 years and over - 1,200 mg/day

Vitamin D is needed to help the body absorb calcium. When choosing calcium supplements, look for ones that also contain vitamin D.

Side effects and safety

Do not take more than the recommended amount of calcium without your doctor's approval.

Drinking more fluids and eating high-fiber foods may solve some of the side effects of taking extra calcium. If these simple measures do not help, try another form of calcium.

Always tell your health care provider and pharmacist if you are taking extra calcium. Calcium supplements may change the way your body absorbs medicines and antibiotics such as tetracycline, as well as iron pills you may be taking. Taking higher amounts of calcium over a long period of time raises the risk of kidney stones in some people.


Calcium Supplements: What to Look for: NIH Osteoporosis and Related Bone Diseases National Resource Center. Reviewed January 2011. Accessed February 22, 2011.

Sarubin Fragaakis A, Thomson C. The Health Professional's Guide to Popular Dietary Supplements. 3rd ed. Chicago, Il: American Dietetic Association;2007.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. National Academy Press, Washington, DC, 2010.

Review Date: 2/14/2011
Reviewed By: David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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