How much calcium can the body absorb at one time?

Absorption is highest at doses of 500 mg or less.^[1] In 37 healthy adults, the body absorbed 36% of a 300 mg dose and 28% of a 1,000 mg dose, both taken with a light breakfast.^[2] That is about 108 mg and 280 mg.

A larger share is absorbed from less calcium in general: about 45% when intake is 200 mg a day and 15% when it is above 2,000 mg a day.^[1] Common supplements contain 500 or 600 mg of calcium per dose.^[1] Smaller doses taken more often can also ease stomach problems.^[1]