Background. As it is established that diabetes mellitus causes metabolic disturbances of all types (first of all because of carbohydrate metabolism), affection of blood vessels, nerves, different organs and tissues. However, the influence of DM on the level of microelements is still not investigated enough. Despite the sufficient variety of medicaments, compensation of diabetes mellitus is achieved in less than 30% of patients. For this reason, the search of new ways of treatment which are aimed at the improvement of carbohydrate metabolism is an urgent issue. Objective. The research was aimed to reveal the deficiency of 25-hydroxyvitamin D3 [25(OH)D3] and its correlation with carbohydrate metabolism. Methods. Thirty five patients with diabetes mellitus Type 2 aged 55-74 with illness duration 2-4 years were examined. The control group included 35 healthy people of the same age and sex. Levels of 25-hydroxyvitamin D3 [25(OH)D3] were tested by means of radioimmunoassay. The level of glycated haemoglobin was tested by means of liquid chromatography. Results. Correlation of the level of vitamin D with the degree of diabetes mellitus Type 2 compensation has been detected. Conclusions. A clear tendency to the improvement of diabetes mellitus Type 2 compensation after medication correction with vitamin D was evidenced.