Calcium requires adequate vitamin D in order to be absorbed by the body. In the United States, many food sources of calcium such as milk are fortified with vitamin D.
Review Date 1/21/2020
Updated by: Gordon A. Starkebaum, MD, MACR, ABIM Board Certified in Rheumatology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.