In addition, some calcium supplements are combined with vitamins and other minerals. For instance, some calcium supplements may also contain vitamin D or magnesium. Check the ingredient list to see which form of calcium your calcium supplement is and what other nutrients it may contain. This information is important if you have any health or dietary concerns.

Choosing calcium supplements

To determine which calcium supplement may be best for you, consider these factors:

Amount of calcium
Elemental calcium is key because it's the actual amount of calcium in the supplement. It's what your body absorbs for bone growth and other health benefits. The Supplement Facts label on calcium supplements is helpful in determining how much calcium is in one serving. As an example, calcium carbonate is 40 percent elemental calcium, so 1,250 milligrams (mg) of calcium carbonate contains 500 mg of elemental calcium. Be sure to note the serving size (number of tablets) when determining how much calcium is in one serving.

Calcium supplements cause few, if any, side effects. But side effects can sometimes occur, including gas, constipation and bloating. In general, calcium carbonate is the most constipating. You may need to try a few different brands or types of calcium supplements to find one that you tolerate the best.

What prescriptions you take
Calcium supplements can interact with many different prescription medications, including blood pressure medications, synthetic thyroid hormones, bisphosphonates, antibiotics and calcium channel blockers. Ask your doctor or pharmacist about possible interactions and which type of calcium supplement would work for you.

Quality and cost
Manufacturers are responsible for ensuring that supplements are safe and claims are truthful. Some companies may have their products independently tested by the U.S. Pharmacopeia(USP) or Consumer Labs (CL). Supplements that bear the USP or CL abbreviation meet voluntary industry standards for quality, purity, potency, and tablet disintegration or dissolution. Different types of calcium supplements have different costs. Comparison shop if cost is a factor for you.

Supplement form
Calcium supplements are available in a variety of forms, including tablets, capsules, chews, liquids and powders. If you have trouble swallowing pills, you may want a chewable or liquid calcium supplement.

Your body must be able to absorb the calcium for it to be effective. All varieties of calcium supplements are better absorbed when taken in small doses (500 mg or less) at mealtimes. Calcium citrate is absorbed equally well when taken with or without food and is a form recommended for individuals with low stomach acid (more common in individuals 50 and older, or if taking stomach acid blockers), inflammatory bowel disease or absorption disorders.

Do calcium supplements have risks?

Calcium supplements aren't for everyone. For instance, if you have a health condition that causes excess calcium in your bloodstream (hypercalcemia), you should avoid calcium supplements. If you aren't sure if calcium supplements are appropriate for your situation, talk to your doctor.

It's not definitive, but there may be a link between calcium supplements and heart disease. It's thought that the calcium in supplements could make its way into fatty plaques in your arteries — a condition called atherosclerosis — causing those plaques to harden and increasing your risk of heart attack. More research is needed before doctors know the effect calcium supplements may have on heart attack risk.

There is similar controversy about calcium and prostate cancer. Some studies have shown that high calcium intake from dairy products and supplements may increase risk whereas another more recent study showed no increased risk of prostate cancer associated with total calcium, dietary calcium or supplemental calcium intakes.

As with any health issue, it's important to talk to your doctor to determine what's right for you.

More isn't always better: Too much calcium has risks

Dietary calcium is generally safe, but more isn't necessarily better, and excessive calcium doesn't provide extra bone protection. In fact, if the calcium in your diet and from supplements exceeds the tolerable upper limit, you could increase your risk of health problems, such as:

  • Kidney stones
  • Prostate cancer
  • Constipation
  • Calcium buildup in your blood vessels
  • Impaired absorption of iron and zinc

If you take calcium supplements and eat calcium-fortified foods, you may be getting more calcium than you realize. Check food and supplement labels to monitor how much calcium you're getting a day and whether you're achieving the RDA but not exceeding the recommended upper limit.