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-sensitivepotassium (KATP) channels. It is selective for pancreatic β-cell over cardiac and arterial smooth muscle cell KATPchannels. 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).