[Vitamin D insufficiency/deficiency:its clinical significance and treatment]

Vitamin D insufficiency/deficiency, a medical condition in which vitamin D store is decreased, is the most frequent cause of decreased action of vitamin D. Severer form vitamin D deficiency can cause hypocalcemia and rickets/osteomalacia. Milder form vitamin D insufficiency also harms bone health via secondary hyperparathyroidism, the increase in fracture risk, and poor responses to anti-osteoporotic medications. Diagnosis can only be made by measuring serum 25(OH)D, which is not currently covered by the Japanese health insurance policy. In Japan, the guideline for the diagnosis vitamin D insufficiency/deficiency is in the process of drafting. According to the current provisional guideline draft that was made in public, vitamin D deficiency would be defined by serum 25(OH)D level less than 20 ng/mL whereas vitamin D insufficiency would refer to the state in which serum 25(OH)D level is between 20 and 30 ng/mL.