TCF7L2 gene is polymorphic, and a number of loci have been identified, such as the rs10749127, rs10787475, rs11196224, rs12775879, rs17130188, rs290481, rs290487, rs290489, rs3750804, rs4918792, rs6585194, rs7085532, rs7094463, rs7919409, and rs966227, rs7903146, rs11196205 and rs12255372 polymorphisms, etc. Among these single nucleotide polymorphisms (SNPs), the TCF7L2 rs7903146 polymorphism are widely studied for the potential relationship with T2DM susceptibility. This evidence concerns the gene TCF7L2 and type 2 diabetes mellitus.