Data on File. There Is a Difference Between Supplements With at least a dozen common calcium preparations and hundreds of different formulations available, choosing a calcium supplement can be confusing.
Most calcium supplements contain calcium carbonate, calcium citrate, or calcium phosphate.
These calcium preparations differ in a number of ways. The manufacturers of calcium carbonate and calcium phosphate supplements recommend their products be taken with meals in order to be used by the body. The combination of these two properties is called bioavailability. The greater the bioavailability of calcium, the better able your body is to use it. Also, calcium carbonate and calcium phosphate supplements need stomach acid to be absorbed.