Objective: This study aimed to investigate the correlation between serum copeptin and glomerular filtration rate (GFR) in type 2 diabetes mellitus (T2DM) patients and to investigate the role of serum copeptin in the diagnosis of early DN in T2DM patients. Methods: 120 T2DM inpatients were recruited and divided into 2 groups according to 24-h urine albumin excretion (UAE): normal UAE group (UAE