Vitamin D is indispensable for the maintenance of bone and
mineral health. Inadequate
vitamin D action increases the risk for various musculoskeletal/
mineral events including fracture, fall,
secondary hyperparathyroidism, diminished response to antiresorptives,
rickets/
osteomalacia, and
hypocalcemia. Its most common cause in recent years is
vitamin D deficiency/insufficiency, clinically defined by low serum
25-hydroxyvitamin D [25(
OH)D] level. Guidelines for
vitamin D insufficiency/deficiency defined by serum 25(
OH)D concentrations have been published all over the world. In Japan, however, the information on the associations between serum 25(
OH)D and bone and
mineral disorders has not been widely shared among healthcare providers, partly because its measurement had not been reimbursed with national medical insurance policy until August 2016. We have set out to collect and analyze Japanese data on the relationship between serum 25(
OH)D concentration and bone and
mineral events. Integrating these domestic data and published guidelines worldwide, here we present the following assessment criteria for
vitamin D sufficiency/insufficiency/deficiency using serum 25(
OH)D level in Japan. 1) Serum 25(
OH)D level equal to or above 30 ng/mL is considered to be
vitamin D sufficient. 2) Serum 25(
OH)D level less than 30 ng/mL but not less than 20 ng/mL is considered to be
vitamin D insufficient. 3) Serum 25(
OH)D level less than 20 ng/mL is considered to be
vitamin D deficient. We believe that these criteria will be clinically helpful in the assessment of serum 25(
OH)D concentrations and further expect that they will form a basis for the future development of guidelines for the management of
vitamin D deficiency/insufficiency.