OBJECTIVES: To analyze the clinical and economic impact of adequate control of glycosylated hemoglobin (HbA1c) over the chronic complications of Type-2 Diabetes mellitus. METHODS: A Monte Carlo simulation was performed termed Diabetes Mellitus Model (DMM), previously validated, and published. The influence parameter of DMM was (HbA1c) simulated for each patient. A temporary horizon of five years was set. The design compared two hypothetical groups of 1000 patients each, with identical parameters. Group one included patients not responding to conventional treatment with insulin, who initiated with a serum level of 9.1% of HbA1c the first year and remained at this value during the four following years. This HbA1c value corresponds to the average level seen in the Mexican population when initially treated (first level of attention). Group two included patients responding to intensive treatment with insulin, who initiated with 9.1% HbA1c and reached an average value of 7.5% HbA1c. The cost of complications was calculated through the estimation of the direct cost. RESULTS: There were 209.69 events in group one, and 160.44 events in group two, a difference of 43.65. There were 7.01 more hypoglycemic events in the group two. Group one had 17.01 more cases of clinical neuropathy, with an estimated cost of €1715.51 per/event. For diabetic foot syndrome there were 2.31 more in group one with a cost of €5180.35 annually. The model projected more cases of microalbuminuria, who without adequate treatment would progress to advanced renal disease, and 1.61 more events of advanced renal disease with an annual cost of €22,273.35. CONCLUSION: The model results justify prevention measures in the first level of attention emphasizing in the strict metabolic control to reduce the start of the micro-vascular damage of target organs; reducing the demand of hospitalization, labor incapacities and use of high-specialty medications which represent the highest costs of the health system.