Look for the amount of "elemental" calcium contained in the product. Elemental calcium is the amount of calcium, given in milligrams (mg) per tablet, that can be absorbed and used by your body. For example, the information on a product label may say that the product contains 500 mg of calcium per tablet and that only 300 mg per tablet is elemental calcium. This means that your body will only be able to absorb and use 300 mg of calcium per tablet.
I never knew that about calcium. What happens to the rest, is it not absorbed, not used by the body? Then why isn't the whole dose just the elemental calcium????