During the past decade, major advances have reported the importance of the vitamin D on the bone metabolism, and recent studies have suggested the potential non skeletal effects of the vitamin D. Adequate vitamin D contributes to reduce the risk of non vertebral fractures, improves the neuromuscular function and reduces the risk of falls when serum 25OHD level are greater than 30ng/mL (75nmol/L). A possible role of vitamin D has been implicated in the reduction of mortality, of the non-skin cancers, of the risk of infections, of inflammatory diseases, of cardiovascular diseases and maybe osteoarthritis. However the current level of evidence for associations is weaker than for skeletal effects. Serum 25OHD level is influenced by several factors (cutaneous vitamin D production, fat mass, dietary sources, UV-B exposure, latitude, season...), and the measurement of the serum 25OHD level is the only way to determine the vitamin D status. It is recommended to measure the serum 25OHD level in patients with osteoporosis or at risk of osteoporosis, and to correct the deficiency.