Our previous studies suggested that the polymorphisms in SLC22A2 (808G→T) and SLC47A1 (rs2289669G→A) could both enhance the long‐term glucose‐lowering effect of metformin via influencing its pharmacokinetics in Chinese type 2 diabetes patients 9, 10. The gene discussed is SLC22A2; the disease is type 2 diabetes mellitus.