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 5/17/2018
Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.