Coronavirus disease 2019 (COVID-19) is caused by infection with severe acute respiratory syndrome corona virus 2. High age, hypertension, diabetes, and obesity are risk factors for severe COVID-19 with increased mortality. In this review, we discuss potential mechanisms by which diabetes and obesity modulate the host viral interactions and host-immune response. Glucose levels should be monitored rigorously, and patient-tailored aggressive treatment of hyperglycaemia is recommended, often with the use of insulin. Persons with diabetes and obesity are susceptible to severe outcomes from COVID-19.