VDR and type 2 diabetes mellitus: Therefore, we conducted a cross-sectional study of patients with type 2 diabetes to elucidate 1) which is a stronger factor in the association with eGFR levels and CKD stages, 25OHD or 1,25OHD, and 2) if there is any interaction between 25OHD/1,25OHD and VDR polymorphisms, in association with CKD stages, after adjusting for other confounders.