Worldwide, more than 350 million people have diabetes, and this number is increasing rapidly. Diabetes is characterized by dangerous amounts of sugar (glucose) in the blood. Blood sugar levels are normally controlled by insulin, a hormone produced by the pancreas. In people with type 2 diabetes (the most common form of diabetes), blood sugar control fails because the fat and muscle cells that usually respond to insulin by removing excess sugar from the blood become less responsive to insulin. Type 2 diabetes can be controlled with diet and exercise and with antidiabetic pills, each of which works in a different way to maintain a healthy blood sugar level. Metformin, for example, stops the liver making glucose and increases the body's response to insulin, whereas sulfonylureas help the pancreas make more insulin. The long-term complications of diabetes, which include an increased risk of cardiovascular problems such as heart disease and stroke, reduce the life expectancy of people with diabetes by about ten years compared to people without diabetes.