In this retrospective analysis of the real-world health data, we performed a retrospective cohort study to investigate differential infection risks of oral antidiabetics in insulin-treated T2DM patients by designing two comparison pairs: (1) DPP-4 inhibitor + insulin combination versus metformin + insulin combination; (2) SGLT-2 inhibitor + insulin combination versus metformin + insulin combination. Here, DPP4 is linked to type 2 diabetes mellitus.