It was found that the role of OCT1, which is responsible for changes in Metformin concentration, has significant association with Metformin intolerance through alteration in its function.[29,86] Moreover, a recent study, among patients with T2DM using Metformin, suggested that changes in certain OCT1 genotype functions significantly increases the likelihood of Metformin induced adverse effects. Here, POU2F1 is linked to type 2 diabetes mellitus.