A compilation of comprehensive information has been presented in this book regarding the pathophysiology of diabetes mellitus. Diabetes mellitus is a complex, progressive disease, which bring along with it, a number of complications. It is a metabolic disease of the endocrine system and is considered one of the most general diseases across the globe. This disease is a universal metabolic epidemic and it is predicted that the number of people affected by this disorder will increase from the present 150 million to around 230 million by 2025. Hyperglycemia is a characteristic aspect of diabetes mellitus and chronic hyperglycemia could result in long-term problems in the eyes, blood vessels, heart and nerves. This book discusses the pathophysiology and selected problems in diabetes mellitus.