Diabetes mellitus is a prevalent disease that affects millions of people worldwide and has paralleled the growing population of overweight and obese individuals. Early detection of prediabetes and diabetes, as well as lifestyle interventions including diet and exercise, are the overarching objectives in preventing and managing diabetes. For individuals who do not achieve glycemic control with lifestyle modification, there are newer medication classes that assist with weight loss, more physiologic insulins with convenient delivery systems, and old standbys like metformin and thiazolidinediones. Glycemic control along with blood pressure and cholesterol management reduce microvascular and macrovascular disease including cardiovascular events. Mounting evidence demonstrates that diabetes is a risk factor for periodontitis and possibly oral premalignancies and oral cancer. The systemic inflammatory response generated by inflamed periodontal tissue may in turn exacerbate diabetes, worsen cardiovascular outcomes, and increase mortality. Thus, oral medical and surgical physicians are vital in treating oral pathology, recognizing new cases of diabetes, and counseling people with diabetes to promote oral health. This article presents updates in the diagnosis, risk factors, prevention, management, and peri-oral complications of diabetes to assist oral health professionals in providing optimal care to patients with diabetes.