The major role of vitamin D in humans is to increase the absorption of calcium and phosphatase for the mineralization of the skeleton. The synthesis of vitamin D3 in the skin under influence of UV light decreases with aging due to insufficient sunlight exposure, and a decreased functional capacity of the skin. Deficiency in vitamin D causes secondary hyperparathyroidism, high bone turnover, bone loss, mineralization defects, proximal myopathy, falls and hip and other fractures. The goal of therapy of hypovitaminosis D is to restore normal serum and deposits of 25 (OH) D. The daily supplementation of vitamin D indicated is about 800-1,000 IU/day but may increase up to a maximum dose of 2,000 IU/day in conditions of severe vitamin D deficiency with a concomitant reduced or no sun exposure, reduced dietary intake and reduced calcium absorption.