Background.Hyperglycemia is leading to serious chronic and acute complications in diabetes mellitus which are shortening and altering the patient’s life. Objective. The main purpose of the study is to investigate the correlation between HbA1c values and diabetic complications. Material and methods.The study enrolled 2120 diabetic patients, 1174 women (55.4%) and 946 men (44.6%), mean age 58.3 ± 12.3 years, living in Timisoara. Results.We observed the lowest incidence of chronic complications of diabetes mellitus for the group having HbA1c values lower than 6%. Chronic complications are increasing with the HbA1c value, with a significant threshold at 7 % (p<0.0001). Conclusions.Optimizing glycemic control is the key to prevent or delay the occurrence of severe chronic complications of diabetes mellitus, complications which can be significantly reduced by achieving the ADA recommended HbA1c target (<7%).