This present study aims to evaluate the distribution of Native American (NATAM), European (EUR), and African (AFR) ancestry in Ecuadorian T2DM patients and its correlation with 19 variants of the seven genes (CYP2C8, CYP2C9, CYP2C19, SLC22A1, SLC22A2, SLC22A3, and ABCB1) that encode the relevant enzymes and transporters implicated in the pharmacogenetics of antidiabetic drugs. This evidence concerns the gene SLC22A3 and type 2 diabetes mellitus.