The course of type 2 diabetes mellitus in COVID-19

Abstract

The coronavirus disease 2019 (COVID-19) pandemic has exposed a profound and bidirectional relationship with type 2 diabetes mellitus (T2DM). This article reviews the course of T2DM in the context of SARS-CoV-2 infection, examining the pathophysiological mechanisms that underpin this dangerous intersection. Patients with T2DM face a significantly elevated risk of severe COVID-19 outcomes, including acute respiratory distress syndrome, hyperinflammatory states, and mortality. The virus exploits the pre-existing metabolic milieu of chronic hyperglycemia, insulin resistance, and low-grade inflammation, creating a permissive environment for viral entry, dysregulated immune responses, and thrombo-inflammatory complications. Furthermore, the course of T2DM itself is often acutely destabilized during infection, manifesting as severe hyperglycemia, diabetic ketoacidosis, and hyperosmolar hyperglycemic state, driven by the stress response, cytokine storm, and direct viral effects on pancreatic beta-cells. Beyond the acute phase, a significant proportion of survivors experience new-onset hyperglycemia, accelerated insulin resistance, or a transition to more intensive glucose-lowering regimens, suggesting a lasting metabolic scar. This article synthesizes current evidence on the acute and chronic interplay between T2DM and COVID-19, emphasizing the need for integrated, multidisciplinary management strategies that address both the infectious and metabolic challenges to improve immediate and long-term patient outcomes.