In our nationwide observational cohort study, based on the large register database, there was statistical evidence that the use of metformin, DPP-4 inhibitors, SGLT2 inhibitors, and arGLP-1 in people with T2DM before COVID-19 infection is associated with a lower fatality rate compared to those who did not use these drugs before COVID-19. Here, DPP4 is linked to type 2 diabetes mellitus.