Diabetes mellitus is a group of physiological dysfunctions characterised by increased blood glucose level resulting directly from insulin resistance or impaired insulin secretion leading to micro and macrovascular complications. The oral complications of diabetes mellitus includes increased incidence of dental caries, dry mouth, burning mouth syndrome and periodontitis. Assessment of blood glucose levels is essential prior to any specialised procedure to avert any further oral and systemic complications. Screening of diabetes mellitus condition has become a necessity in developing countries and study of this nature will have enormous public health impact. The aim of this study is to assess the prevalence of diabetes mellitus in patients visiting different outpatient departments of private dental college hospital, Chennai. All the cases referred from the month of June 2019 to March 2020 for random blood sugar tests were chosen for the study. Data was collected from the dental hospital record system. Result data was tabulated in excel and imported to SPSS for correlation and association. P<0.05 was considered to be the level of statistical significance in this study. Within the limits of the present study, diabetes mellitus prevalence in random blood sugar tested patients is 33.3 % with a higher male incidence and more prevalent among the age group of 41 to 60 years. Knowledge about the prevalence of diabetes mellitus in the patients visiting dental hospital will be helpful to the clinician to prevent any further complications before any specialised procedure.