Calcium bioavailability from calcium carbonate and calcium citrate

J Clin Endocrinol Metab. 1985 Aug;61(2):391-3. doi: 10.1210/jcem-61-2-391.


Fourteen normal subjects took 1000 mg calcium orally as calcium citrate or calcium carbonate. The amount of calcium absorbed was estimated from the rise in urinary calcium. The urinary calcium following calcium citrate load significantly higher (by 20-66%), whether expressed as the total amount or as the increment above basal (fasting) excretion. Thus, calcium citrate provides a more optimum calcium bioavailability than calcium carbonate.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Administration, Oral
  • Adult
  • Biological Availability
  • Calcium / blood*
  • Calcium Carbonate / administration & dosage*
  • Calcium Carbonate / metabolism
  • Citrates / administration & dosage*
  • Citrates / metabolism
  • Citric Acid
  • Female
  • Humans
  • Intestinal Absorption
  • Male
  • Solubility


  • Citrates
  • Citric Acid
  • Calcium Carbonate
  • Calcium