What Is the Best Calcium Supplement?

Ask the experts

I've heard that not all calcium supplements are the same. Which over-the-counter vitamins or minerals help build bones? Which brands or types are better than others?

Doctor's response

You heard right, not all calcium supplements are the same. The supplements will differ by the kinds of calcium that they contain, the amount that they contain, and any thing else that is added to them (other minerals or vitamins). Along with that, there are other factors that will affect how much of the calcium you will actually absorb, including medications that you are taking, your age, your vitamin D levels, the amount of calcium that you are taking and if you are pregnant. If you have any concerns over any of these, it would be best to speak with your physician before taking anything.

The most common forms of calcium in supplements are calcium carbonate and calcium citrate. The differences between the two are:

    Calcium carbonate
    • Less expensive
    • Don't need to take as many pills to get your calcium requirements
    • If you have low acid in your stomach (achlorhydria), you will have trouble with absorbing this
    • May be constipating
    Calcium citrate
    • More expensive
    • You will need to take more pills to meet your calcium requirements
    • This does not need acid to be absorbed, so it works well for anyone with achlorhydria

When choosing your supplement, you will need to check out the label to see how much elemental calcium is in it. This is the actual amount of calcium that your body absorbs. You will not want to take in more than 500 mg of calcium at one time, including that from food and supplements. The Recommended Adequate Intake for calcium is based on your age:

  • 0 to 6 months - 210 mg
  • 7 to 12 months - 270 mg
  • 1 to 3 years - 500 mg
  • 4 to 8 years - 800 mg
  • 9 to 13 years - 1300 mg
  • 14 to 18 years - 1300 mg
  • 19 to 50 years - 1000 mg
  • 51+ years - 1200 mg

There is not one brand that I recommend. You can look for the voluntary USP (United States Pharmacopeia) symbol. This means that the product is free of lead and meets the standards of quality of elemental calcium and how well it dissolves. There are products without this symbol that may also meet these standards. One test that you can do to see how well the tablet dissolves is to place it in clear vinegar, stir occasionally and see how it dissolves in 30 minutes. The reason that this is important is that it will need to dissolve in you in order to be absorbed, so seeing that it dissolves completely in the vinegar means that it will do the same in you.

While it is important to get an adequate amount of calcium in your diet, you do not want to go overboard and take excessive amounts. Many people follow the thought that if something is good for you then more is better, but that is not always the case with vitamins and minerals. In fact, excessive amounts of some vitamins and minerals can end up damaging your health. For this reason, Tolerable Upper Limit (UL) levels have been established to let people know the number that you do not want to go beyond when taking supplements. The UL for calcium for children over 1 and adults is currently set at 2500 mg/day. Going beyond that can interfere with your body's ability to absorb other minerals (iron, phosphorus, zinc, and magnesium), it can impair how your kidneys function, it can elevate your blood levels of calcium (hypercalcemia), and it could end up interfering with other medication that you are taking. Sticking with the Recommended Adequate Intake levels is your safest bet—no bones about it.

Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


"Regulation of calcium and phosphate balance"