[Vitamin D supplementation for chronic kidney disease according to the guideline issued by DOQI].

Supplementation of vitamin D in food is available in Japan, therefore, vitamin D deficiency is not likely to occur in our country. But, in the case of nephrotic syndrome and strict dietary protein restriction, low serum 25(OH)D level might develop in chronic kidney disease (CKD)patients. Guideline issued by National Kidney Foundation as DOQI recommend the use of vitamin D2 (ergocalciferol) when serum 25(OH)D level in CKD patients become less than 30 ng/mL. In addition, for the CKD patients with stage 5, the use of active vitamin D3 is recommended because a conversion to 1,25(OH)2D3, which is the most potent vitamin D, might be impossible in these patients. However, vitamin D2 product as a supplementary medicine is not available in Japan unfortunately. In this context, I try to explain the background of the recommendation of vitamin D2 for CKD patients.