Evaluating Calcium Supplements
When evaluating a calcium supplement, one of the key issues to consider is the level of
elemental calcium, rather than the amount of calcium salt. It is the level of elemental calcium that determines how many tablets will be needed to achieve your RDI.
The following table sets out the level of elemental calcium contained in some popular calcium salts.
7 It can be seen from the table that calcium carbonate, as contained in Caltrate contains the most elemental calcium per 1000mg, making it the most concentrated form of calcium available.
| Calcium Salt |
Elemental Calcium per 1000mg |
| Calcium carbonate |
400mg |
| Calcium citrate (tetrahydrate) |
211mg |
| Calcium lactate (pentahydrate) |
130mg |
| Calcium gluconate (monohydrate) |
89mg |
The calcium carbonate dissolves readily under the acid conditions present in the stomach after a meal.
8,9 Therefore, when taking a supplement containing calcium carbonate, it should be taken after a meal.