BACKGROUND: The novel coronavirus disease (COVID-19), declared a global pandemic by the World Health Organization (WHO) on March 11, 2020, has constituted one of the most serious health challenges of the century, globally. The causative organism was initially named the 2019 novel coronavirus (2019 nCoV) but has subsequently been renamed Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The pandemic has so far infected several million and killed about a million people worldwide. Diabetes mellitus (DM) is one of the leading causes of morbidity worldwide. OBJECTIVES: To examine the critical role diabetes plays in the pathogenesis and prognosis of COVID-19 and to assess the emerging therapies available to fight the pandemic. METHODS: Authors conducted a systematic review of literature to examine the role of diabetes as a comorbidity in the pathogenesis and prognosis of COVID-19. RESULTS: Both experimental and observational data from early 2020 suggested that most people with COVID-19 have comorbidities, the most dominant of which are diabetes, cardiovascular disease, and hypertension. Empirical evidence indicates that diabetic patients infected with the COVID-19 disease had the worst outcomes concerning morbidity and mortality. CONCLUSION: A combination of underlying chronic conditions such as hypertension, obesity, and cardiovascular diseases together with altered ACE receptor expression, immune dysregulation via cytokine storm, alveolar and endothelial dysfunction, increased systemic coagulation may put individuals with diabetes at risk for COVID-19 severity. More studies are needed to elucidate how glucose-lowering drugs may modulate the host immune response in diabetic individuals, especially following the administration of potential COVID-19 vaccines.