Various calcium supplements are available for patients who have an indication for calcium suppletion.
American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids.
The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate absorption.
No convincing scientific evidence supporting the advice to prescribe calcium citrate instead of calcium carbonate to patients who also take antacids is available, and therefore deserves further investigation.
On the contrary, the fact that calcium carbonate does not need acid in order to be absorbed, has also not been proven.
In clinical practise, it appears important that calcium is taken with meals in order to improve its absorption.
Conflict of interest: G. Huls and his institution of employment received a fee from Celgene for lecturing at MDS Colloquium, Vienna, 2011. Financial support for this article: none declared.