The article presents the modern ideas about post-COVID syndrome, indicates various types and classifications of post-COVID syndrome, provides epidemiological data, including the patients with type 2 diabetes, also the definition of post-COVID syndrome is given. The group of patients defined as patients with post-COVID syndrome is very heterogeneous. Post-COVID syndrome is more common in the elderly, with comorbid pathology, severe disease. The pathophysiology of this syndrome in patients with type 2 diabetes mellitus is analyzed, and risk factors are indicated. The main biomarkers of disorders were determined: monocytes and their coefficients, acute phase proteins, some biochemical indicators, including analysis of genetic associations with the severity of post-COVID disorders (interferon gamma gene, methylenetetrahydrofolate reductase gene, ACE2 inhibitor). Genotyping of a sample of 26 single nucleotide polymorphisms in genes implicated in viral entry, immune response, and inflammation were significantly associated not only with the risk of long-term COVID-19 symptoms, but also with the cumulative incidence of post-COVID syndrome. Elevated levels of interleukin 6, C-reactive protein and tumor necrosis factor alpha may serve as potential diagnostic biomarkers in long-term COVID biomarkers of blood vascular transformation have great potential for diagnosis, and angiogenesis modulators may have therapeutic efficacy It has been shown that the vast majority of patients, in particular those suffering from type 2 diabetes, develop post-COVID-19 syndrome, and taking into account pre-existing diseases, post-COVID syndrome is not so harmless. By identifying common biomarkers and genetic associations, it is possible to identify the common molecular mechanism of post-COVID syndrome COVID-19 and diabetes mellitus. The novelty of disease association studies in the context of COVID-19 provides new insights into the management of rapidly evolving long-term COVID and post-COVID syndromes that have significant global implications.