Given the diversity of populations and the limited pharmacogenetics studies in Mexico, along with variable outcomes, this study aims to determine the genotype and allele frequencies of seven SLC22A1 genetic variants that had been reported in Hispanic and Caucasian populations (rs622342, rs628031, rs72552763, rs12208357, rs34130495, rs34059508, and rs2282143) and to assess their association with glycemic control in individuals with T2DM undergoing metformin monotherapy in Northern Mexico. The gene discussed is SLC22A1; the disease is type 2 diabetes mellitus.