Objective; of the this study was to investigate the effect of sitagliptin on blood glucose ,oxidative stress and total antioxidant status (TAS) in people with type 2 diabetes mellitus. Design: Case-control study Selection; The patients were selected from main diabetic clinics in al-Wafaa’ Diabetic Clinic and from private clinics in Mosul city during the period from 1st of November 2020 to the 30 t h April 2021. Methods; It was conducted randomly 60 patients (32 males , 28 females ) of Non-insulin diabetes mellitus , who were already on routine anti-diabetic therapy ,those separated into 2groups. First Group : included 30 patients( 17 males,13 females) of T2DM treated with oral metformin alone Second group : included 30 patients( 15 males ,15 females) of T2DM treated with combination of Sitagliptin + metformin for at least 3 months , measured fasting plasma glucose, glycosylated hemoglobin another 30 healthy subjects , age ,sex matched with the patients, were considered as a control groups . Malondialdehyde (MDA) and Total antioxidant status (TAS) were measured in all groups Results; of this study, serum MDA levels were found high and TAS concentrations was lower in diabetic patients of both groups than the healthy control, the combination of sitagliptin + metformin caused significant reduction( P-value > 0.05) in the level of glycosylated hemoglobin ( HBA1c ) and malondialdehyde (MDA) in comparison with group that received metformin monotherapy ,as well as ,non-significant change in fasting blood group( FBG) and total antioxidant status (TAS )in both groups As a conclusion of the present study sitagliptin can attenuated MDA in patient with NIDDM and greater reduction in serum level of HBA1c than the use of metformin monotherapy.