The association of diabetes mellitus and tuberculosis is a public health problem due to the spread of these two epidemics. Literature data confirm that 80-90% of patients develop tuberculosis on the background of pre-existent diabetes. Basing on the clinical situation and the pharmacodynamic features of oral antidiabetics, patients with type 2 diabetes are recommended to switch to insulin-containing medicines. Current data on the pharmacological effects of metformin support the benefit of the medicine in the course of diabetes mellitus and tuberculosis. A retrospective study was performed on 48 case histories of patients, aged between 19 and 80 years, suffering from infiltrative pulmonary tuberculosis and type 2 diabetes mellitus. The prescribed antidiabetic treatment, the frequency of metformin use and the reasoning of the oral antidiabetic administration in these cases were analyzed. According to the case histories studied, the patients with undercompensated or decompensated type 2 diabetes were treated with insulin-containing medicines, based on the advice of the endocrinologist. The antidiabetic treatment included: combination of short- and medium-acting insulins - 21 cases, medium-acting insulins - 11 cases, combination of metformin and insulin - 7 cases and 9 patients with type 2 diabetes used metformin. The potential beneficial effects of metformin in patients with diabetes mellitus and tuberculosis can be determined by the following: production of reactive oxygen species inhibiting the growth of mycobacteria; blocking the o phosphorylation system of Mycobacterium tuberculosis; suppression of energy production required for bacterial growth by directly inhibiting the mitochondrial-1 complex of electron transport; inhibition of the mycobacterial folic acid cycle; reducing mycobacterial virulence by blocking mitochondrial glycerophosphate dehydrogenase and inhibiting gluconeogenesis modification of the intestinal microbiota by mediating the immune response and reducing insulin resistance; inducing the formation of the phagolysosome complex and releasing mediators from neutrophils to attract phagocytes to the site of infection; inhibiting the synthesis and increasing the efflux of cholesterol from macrophages affecting the entry mycobacteria into macrophages. Thus, the need of metformin administration in diabetic patients with tuberculosis i strengthened by the metabolic, immunological and antibacterial effects of this drug.