In this cohort study of 382 574 adults with type 2 diabetes aged 58 to 66 years, rates of initiation of glucagonlike peptide-1 receptor agonists, sodium-glucose cotransporter-2 inhibitors, and dipeptidyl peptidase-4 inhibitors were lower among Medicare Advantage enrollees than among commercial health insurance plan enrollees. Here, SLC5A2 is linked to type 2 diabetes mellitus.