Infectious epidemic of COVID-19 caused by the new coronavirus is characterized by severe course in patients with diabetes mellitus, which presents another noninfectious pandemic accelerating for last decades. Today, according to the International Diabetic Federation data, there are 463 million patients with diabetes mellitus in the world. The burden of the COVID-19 epidemic is largely explained by a frequent combination of these two pathologies. From the previous flu epidemics and already available data of the current epidemic, diabetes mellitus and obesity are considered to be the predictors of more severe course of COVID-19 and mortality. On the other hand, SARS-CoV-2 can aggravate diabetes mellitus, via direct damage of pancreatic beta cells and the liver injury, resulting in higher insulin resistance. We discuss the mechanisms underlying the relation between coronavirus infection and diabetes mellitus and consequences of their mutual influence. Also the article reviews potential strategies of personalized therapy in COVID-19. Timely control and maintenance of individualized target glycemic level is the cornerstone of successful prevention of COVID-19 complications. Disease severity defines strategy of treatment and the choice of antihyperglycemic therapy. © 2020 All-Russian Public Organization Antihypertensive League. All rights reserved.