Gliclazide-d4 is intended for use as an internal standard for the quantification of gliclazide by GC- or LC-MS. Gliclazide is a sulfonylurea and an inhibitor of pancreatic β-cell ATP-sensitive potassium (KATP) channels. It is selective for pancreatic β-cell over cardiac and arterial smooth muscle cell KATP channels. Gliclazide (5 μM) increases insulin-induced glucose uptake and glucose transporter 4 (GLUT4) translocation to the plasma membrane in a differentiated 3T3L1 adipocyte model of insulin resistance induced by hydrogen peroxide. Gliclazide (5 and 10 μg/ml) reduces LDL oxidation by human aortic smooth muscle cells (HASMCs), decreasing TBARS content and 8-isoprostane levels. It also decreases oxidized LDL-induced HASMC proliferation and monocyte adhesion when used at concentrations ranging from 1 to 10 μg/ml. Gliclazide (5 mg/kg) reduces serum glucose levels and increases glucose uptake by isolated rat hindquarters in a model of diabetes induced by streptozotocin (STZ).