Purpose: to evaluate changes in metabolic parameters of patients with diabetes mellitus type 2 (DMT2) under the influence of vitamin D treatment. Object and research methods. A total of 164 DMT2 patients with D deficiency aged 19–75 y.o. were included in the prospective study. Patients were divided into 2 groups: 82 patients of the research group received treatment with vitamin D at a dose of 10,000 IU for 3 months, and 82 patients of the control group did not receive vitamin D. All patients were used oral hypoglycemic agents, the doses of which were not changed. The assessment of vitamin D availability was carried out using the «25-hydroxycalciferol» test, which was performed by chemiluminescent immunoassay. Determination of glycated hemoglobin was carried out using the method of high-performance liquid chromatography, determination of total cholesterol was carried out by the colorimetric method. Results. Under the influence of treatment with vitamin D at a dose of 10,000 IU, there was a significant increase in the level of 25-hydroxyvitamin D in the blood of patients of the research group, compared to patients of the control group, a significant positive dynamics of glycated hemoglobin and a tendency to improving of blood cholesterol level. Conclusion. Correction of D-deficiency in patients with DMT2 has an additional positive effect on the normalization of carbohydrate metabolism, contributes to the improvement of fat metabolism.