Background-More research was needed to determine whether metformin use could impact the risk of oral cancer. Methods: During 2015-2025, patients with type 2 diabetes mellitus who had recently started taking metformin (n = 288198, “ever users of metformin”) or other antidiabetic medications (n = 16263, “never users of metformin”) were monitored for oral cancer for at least six months until December 31, 2011.Cox regression adjusted for propensity score (PS) or integrated with the inverse probabili