The objectives of the review was to summarize the comorbidities of patients with COVID-19 and to find out potential factors associated with severe disease, and to describe the treatment summary of Diabetes mellitus in COVID-19 along with describing the severity by comparing the ICU admission and mortality. For reporting systematic review and results, the study had followed PRISMA guidelines which searched pub med, Google scholars to find relevant articles using keywords “COVID-19”, “SARS-CoV2” and Diabetes mellitus. Articles were selected between the period of 3 years (from 2019 to 2021). Extracted data were entered into Microsoft excel and were restrained which includes study designs (e.g., date of conduct, sample size), patient characteristics, study methodology (e.g., eligibility criteria, method of randomization, and blinding), intervention and main results. Characteristics of each patient data was collected on excel sheet and interpreted on various end points and outcomes. Among 13 studies, 5297 patients had Diabetes mellitus as major comorbidity of which male (57.1%) and female were 42.9%. The prevalence of comorbidities varies from (1-12.6%) for smokers, (8 to 41.6%) for HTN, (7.4 to 70.8%) for DM, (1.6 to 23.0%) for CVD, (0.7 to 2.9%) for CKD, (0.5 to 4.6%) for CLD. By comparing the ICU admission patients of COVID-19 with DM without DM, it shows that Covid-19 patients with Diabetes mellitus had more risk of ICU admission (36.8%). In prevalence of survivors versus non-survivors in COVID-19 patients with Diabetes, the survivor rate (62.2%) is higher than non-survivors (13.4%) which illustrate that COVID-19 with Diabetes have less mortality rate. Initial studies found that the male patients had Diabetes mellitus as major comorbidity in COVID-19 when compared to females. The studies of prevalence of comorbidities in COVID-19 shows high prevalence of Diabetes makes it as a major comorbidity in patients with COVID-19. And by comparing the ICU admission patients of COVID-19 with Diabetes and without Diabetes, studies show that COVID-19 associated Diabetes patients have more risk of ICU admission. Then comparing the prevalence of survivors versus non-survivors shows that the COVID-19 patients with Diabetes also have less mortality rate.