Background:Diabetes mellitus continues to be an important clinical problem throughout the world In 2014, 8.5% of adults aged 18 years and older had diabetes. In 2015, diabetes was the direct cause of 1.6 million deaths. Objectives:To investigate the role of retinol binding protein (RBP) in the early stage of diabetic nephropathy, in patients with type 2 diabetes mellitus (T2DM). Methods: This cross-sectional observational study recruited patients with longstanding T2DM and healthy control subjects. Patients with T2DM were further stratified based on their urine albumin–creatinine ratio (UACR). Urinary concentrations of RBP were determined using an enzyme-linked immunosorbent assay.