AimsThiol/disulphide homeostasis plays a critical role in antioxidant defense, and detoxification in body. Although alteration of thiol/disulfide homeostasis had been shown in patients with diabetes, the thiol/disulfide balance in patients with type 2 diabetes and nephropathy is not yet known. MethodsTwenty-six healthy volunteers (group 1), and 17 normal albuminuric (group 2), 24 middle albuminuric (group 3), 20 severe proteinuric (group 4) patients with type 2 diabetes were included. Proteinuria was tested by measuring microalbumin/creatinine ratio in spot urine. Thiol/disulphide homeostasis concentrations were measured using method developed by Erel et al. ResultsMean blood urea and creatinine levels were found to be significantly higher and GFR level was found to be significantly lower in group 4 than in the other groups. Native thiol levels are significantly lower in groups with diabetes than in healthy group and in groups 3 and 4, compared to group 2. Total thiol level was significantly lower in groups 3 and 4 than group 1 and 2. Disulphide/native thiol and disulfide/total thiol ratios were significantly higher in the groups with diabetes than in group 1 and in the group 4 than in the group 2. ConclusionThe level of native and total thiols were found to be decreased significantly with the grade of nephropathy in patients with type 2 diabetes and the balance had been disrupted in favor of disulphide. We suggest that deteriorated thiol/disulphide balance may be one of the important factors in the development or progression of diabetes induced nephropathy.