The paper gives quick-look data on the new area in the diagnosis and treatment of diabetes mellitus (DM) - personalized medicine. It describes difficulties in the diagnosis of DM, its heterogeneity in children and adults, which may be identified by molecular genetic, immunological, hormonal, and metabolic studies. Data on the possibilities of predicting the individual, familial, and population risks of types 1 and 2 DM are presented. Prospects for choosing the most effective and safest glucose-lowering therapy on the basis of a pharmacogenetic analysis of the susceptibility of patients to specific drugs are outlined.