Gliclazide and selegiline have different mechanisms of action, there is no such thing as which one is better, you should choose the right drug according to your condition. 1. Gliclazide is a sulfonylurea hypoglycemic drug, which can stimulate the pancreatic β-cells to secrete insulin, and is suitable for type 2 diabetes mellitus with pancreatic islet secretion function, with the adverse reaction of hypoglycemia, and is prohibited in patients with hepatic and renal insufficiency, as well as in patients with allergy to sulfonylureas. 2. Sitagliptin is a DPP-4 inhibitor, which reduces the inactivation of GLP-1 in the body by inhibiting DPP-4, increases the level of GLP-1 in the body, and promotes the secretion of insulin, the adverse reactions include allergy, renal function impairment, etc. It is prohibited for those who are allergic to it. Gliclazide and selegiline should be rationally applied under the guidance of a doctor according to the condition.