Sleep deprivation is an important risk factor of the metabolic disorder. According to the systematic review published in the Circulation there are a lot of data from epidemiological, clinical and experimental researches which confirm this fact. The goal of our research was to assess the level of glycohemoglibin after the normalization of sleep duration. 24 patients with diabetes mellitus type2 (19 females and 7 males, average age 58.7 ±1.3 yer) were included in the research. Diabetes mellitus type 2 duration was 9.5 years. Criteria excluded were myocardial infarction, stroke, sleep apnea, oncological diseases and depression. To exclude depression we used the questionnaires: Center for Epidemiological Studies Depression Scale and The Hospital Anxiety And Depression Scale. To exclude sleep apnea we used questionnaire STOP-Bang score. The sleep duration was assessed by the patients self-reports. Glycohemoglibin was determined by Immunoinhibition Method Cobas 6000, Roche Diagnostics. The sleep duration was corrected by cognitive behavioral therapy. For statistic assess of the results we used the method Wilcoxon F. Results: At the beginning of the treatment the level of glyhemoglobin was 7.8% and the sleep duration was 6.4 hours.The included patients were treated by cognitive behavioral therapy for 6 months without changing other kinds of therapy. The sleep duration significantly(P=-0.35) enlarged until 7.5±0.2 hours and the level of glyhemoglobin was lowered by 0.4% significantly (P=0.47). The improving of sleep duration can successfully reduce the level of glyhemoglobin in diabetes mellitus type 2 without any intervention at glycemia and could contribute to the prevention of diabetes complications.