Combining the information currently available regarding the pathophysiology of SARS-CoV-2 infection, the negative implications in the body of sustained hyperglycemia related or not to DM, as well as the beneficial effect of glycemic control in COVID-19 patients, indicate the importance of ACE2 in lung protection and its participation in the correct functioning of other tissues, and the deleterious effects of the absence of ACE2. The gene discussed is ACE2; the disease is diabetes mellitus.