Calcium is the most abundant mineral in the human body. Of the two to three pounds of calcium contained in the average body, 99% is located in the bones and teeth. Calcium is needed to form bones and teeth and is also required for blood clotting, transmission of signals in nerve cells, and muscle contraction. NOW Calcium Citrate is a readily digested and absorbed form of Calcium.* The trace minerals and Vitamin D are added because of their essential role in bone metabolism.