[Clinical significance of measuring vitamin D metabolites].

For differential diagnosis of rickets/osteomalacia, it is essential to evaluate the level of circulating vitamin D metabolites. Although many other metabolites are present, it is clinically sufficient to assess 25 (OH) D and 1,25 (OH)(2)D. Low "normal" serum 25 (OH) D level does not cause rickets/osteomalacia, but could harm bone health. Such vitamin D insufficiency or inadequacy, can not be recognized unless serum 25 (OH) D is measured. Currently serum 25 (OH) D measurement is not reimbursed with the national health care system in Japan, to which an action should be taken.