Diabetes Mellitus (DM) is a condition in which a person has a high blood sugar level over a prolonged period. DM arises as a result of complete or relative insufficiency of insulin secretion and/or insulin action. There are three main forms of diabetes, type 1 (insulindependent DM), type 2 (non-insulin-dependent DM) and gestational DM. The incidence of Diabetes Mellitus (DM) has substantially increased worldwide. It is estimated that around 382 million people were affected with diabetes in 2013, and the number is expected to rise to 592 million by 2035. All major types of DM are characterized by hyperglycemia, dyslipidemia, abnormal protein metabolism and oxidative stress. People with DM have an increased risk of developing micro vascular and macrovascular complications later in life. This review focuses on the types of DM and its relative prevalence across the different countries of world. The present review not only updates our knowledge about the DM and its associated secondary complications, but also provides statistics of diabetes prevalence around the world.