Objectives: This present study was to evaluate and compare the adenosine deaminase activity in diabetic and non diabetic subjects. Methods: Detail history, clinical examination and relevant laboratory investigations were performed to all subjects. The level of serum adenosine deaminase (ADA) was determined by using Erba Mannheim Chem 5X Semiautoanalyser based on Photometry. Lipid profile (total cholesterol, triglyceride and HDL–Cholesterol) were also done using AU 5800 Autoanalyser. VLDL–Cholesterol and LDL Cholesterol were calculated using Friedwald’s formula. Results: Data was analyzed by using latest version of IBM SPSS soft ware. Paired samples T Test was performed. Mean, standard deviation and paired samples correlations were observed. P value was taken less than or equal to 0.05 (p≤0.05) for significant differences. Conclusions: Adenosine deaminase activity is significantly increased in diabetic patients when compared to non diabetic subjects. FBS, BMI, TG, VLDL and HDL of diabetic cases are significantly greater with respect to non diabetic subjects. Hence, Increased serum activity of adenosine deaminase activity is a good diagnostic marker of patients with type 2 diabetes mellitus and it might be a marker for insulin therapy indication.