Minerals
Calcium Carbonate
The most concentrated and least expensive form, and also a common antacid. It needs stomach acid to absorb, so it should be taken with food, and it is more likely than citrate to cause gas or constipation.
Best for
Budget supplementation and antacid use
Absorption
Moderate
Tolerability
Take with food; can cause bloating
Typical timing
Citrate any time; carbonate with food. Split doses above 500 mg.
How to take Calcium Carbonate
A typical dose of Calcium: 500–1,000 mg per day from supplements, only to fill dietary gaps. Best timing: Citrate any time; carbonate with food. Split doses above 500 mg.. The form you choose mainly affects absorption and how easily it sits with your stomach, not the overall dose.