Diabetes mellitus is a group of metabolic diseases characterized by high blood glucose levels resulting from defects in insulin production or insulin action. There are several types of diabetes including type 1, type 2, gestational diabetes, and other rare forms. The long-term complications of diabetes include damage to various organs such as the eyes, kidneys, nerves, and heart. Prediabetes is a condition where blood glucose levels are higher than normal but not high enough to be diagnosed as diabetes. Lifestyle changes such as diet and exercise have been shown to prevent or delay the onset of type 2 diabetes in those with prediabetes.