Diabetes mellitus is a chronic disease that can cause devastating systemic complications. Currently, almost 29 million Americans have diabetes, and more than 25% do not know they have the disease. Another 86 million have pre-diabetes. Individuals with diabetes may present with a variety of oral manifestations. Treatment of patients with diabetes requires careful attention to ensure that oral health is maintained and precautions are taken to avoid medical emergencies. This course provides an update on diabetes mellitus, including types of diabetes, etiology, diagnostic studies, treatment, and guidelines for providing oral health care. As oral health care providers, dental professionals have an opportunity to assist individuals with diabetes to manage the oral manifestations of the disease as well as to maintain glycemic control.