Background: This study was conducted to determine the frequency and clinical features of patients who were diagnosed incidentally as having diabetes mellitus (DM) in the emergency department. Aim: Our aim was to investigate the frequency of DM in patients whose high blood glucose levels were detected, and to examine the subsequent treatment these patients. Methods: The participants were selected from among patients who had a glucose level of ≥200 mg/dL and admitted to emergency department with symptoms of hyperglycemia in the past 1 year. Age, sex, presence of chronic disease, and the laboratory blood parameter results of the patients were recorded. We divided the patients into three groups as those who had never been admitted to clinics for treatment, those who were admitted and given treatment, and not given treatment. Results: According to their sexes, 73 (52.1%) were male and 67 (47.9%) were female. It was determined that 86 of the 140 patients included in the study were admitted to clinics for treatment. It was determined that no medication was given to 50 of these patients, but treatment was initiated in 36. Patients with glucose level ≥300 mg/dL were found to be receiving more treatment significantly (p=0.031). Conclusions: In this study, diabetic patients whose blood sugar is between 200-300 mg/dL should be sent to the DM related clinic immediately when diagnosed in the emergency department.