These SNPs fall within genes with a clear relation to drug transport (SLC22A1 and SLC22A2), metabolism (CYP2C9), activity (PPARG and ABCC8), genes that have a direct role in diabetes onset or progression (KCNJ11, IRS1 and TCF7L2) or that have been frequently associated by GWAS to T2D and drug response (CAPN10), despite the fact that the exact mechanisms are still unclear. This evidence concerns the gene TCF7L2 and diabetes mellitus.