Mendelian randomization studies are useful for the identification of causal relationships between associated factors, and in the present study we found that a representative SNP in UGT1A1 is not associated with diabetic vascular complications or the well-established risk factors for vascular disease, suggesting that bilirubin might not play an important role in the development of DR and DKD. Here, UGT1A1 is linked to diabetic kidney disease.