DPP4 and diabetes mellitus: The American Diabetes Association (ADA) guidelines include medications such as metformin, sodium–glucose cotransporter-2 inhibitors (SGLT2 i), glucagon-like peptide receptor agonists (GLP-1 RAs), dipeptidyl peptidase-4 inhibitors (DPP-4 i), thiazolidinediones, and sulfonylureas [2].