This study investigated the possible role of glutathione (GSH) in diabetic complications and its biochemical safety in experimental diabetic rats. Serum biochemical parameters and the histology of the pancreas were investigated. Seven rats were separated as controls. To create the diabetes in rats, 45 mg/kg single-dose streptozotocin (STZ) was administered i.p. The treatment was continued for 1 month. STZ was administered to the diabetes + GSH group, then reduced GSH, dissolved in isotonic salt solution (200 mg/kg), was applied i.p. two times a week. The GSH group received i.p. GSH. Serum biochemical parameters were determined by autoanalyzer. Immunohistochemical procedures were used to determine the percentage of the insulin-immunoreactive β-cell area in the islets of Langerhans. The biochemical parameters changed to different degrees or did not change. Pancreatic cells of the control and GSH groups were healthy, but in the diabetic and GSH-treated diabetic groups we found damage in different numbers. The results from these analyses show that GSH supplementation can exert beneficial effects on pancreatic cells in STZ-induced diabetic rats and can safely be used for therapy in and protection from diabetes and complications of diabetes.