Sitagliptin is an oral dipeptidyl peptidase-4 (DPP-4) inhibitor that enhances active incretin hormone levels (GLP-1 and GIP), thereby increasing glucose-dependent insulin secretion and suppressing glucagon release. It offers a low risk of hypoglycaemia and is weight-neutral. Indicated for the treatment of type 2 diabetes mellitus in adults as monotherapy when diet and exercise are inadequate and metformin is unsuitable, or as add-on combination therapy with metformin, sulphonylureas, thiazolidinediones, or insulin.