This study was designed to check whether insulin supplementation is crucial for inducing diabetic nephropathy (DNP) in Wistar rats. Diabetes was induced by a single intraperitoneal injection of streptozotocin. The urinary biochemical parameters such as albumin, creatinine and urea nitrogen were monitored every two weeks. The histological changes in the kidney were observed at the end of both fifth and seventh month. Immunohistochemical analyses of VEGF, ERK-1 and NF-κB expression were performed to demonstrate mesangial expansion and glomerulosclerosis, which are the defining histological features of nephropathy. A significant change in the urinary biochemistry was observed in diabetic animals at the end of four months, but the aforementioned quantitative changes were delayed in diabetic animals treated with insulin. At the end of seven months, the diabetic animals showed prominent histological changes such as glomerular basement membrane thickening, nodular glomerulosclerosis and mesangial expansion. However, these changes were not observed in diabetic animals treated with insulin even at the end of the study. From the results, it can be concluded that there is no need of insulin supplementation for inducing DNP, when the animals are induced with an optimal dose of 45 mg/kg body weight of streptozotocin.