Abstract : Diabetes is one of the most important comorbidities linked to the severity of infection caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2). The prevalence of diabetic patients hospitalized in intensive care units for COVID-19 is two-to-threefold higher than that observed in non-diabetic patients and a risk of progressing to critical or fatal disease is increased by a factor of 3 to 4 in patients with diabetes. Multiple mechanisms link diabetes as a risk factor of severe COVID-19, including both diabetes-related (such as hyperglycaemia) and diabetes-associated (such as immune dysfunction, obesity and hypertension) components. Optimising glycaemic control to reduce the risk of severe COVID-19 appears important but challenging and the best choice of antidiabetic treatment remains to be established, even if an early introduction of insulin in type 2 diabetes patients with COVID-19 is encouraged upon admission to the hospital. Future investigations are necessary to improve both the management and the prognosis in these very high risk patients.