Diabetes is a chronic and life-threatening disease caused by the body's inability to produce or properly use insulin, a key hormone that the body uses to manage glucose, which fuels the cells in the body. Insulin regulates the uptake of sugar from the blood into the cells. When glucose builds up in the blood instead of going into cells, it can cause the cells to become starved for energy and, over time, damage the eyes, kidneys, nerves or heart. Although not all of the causes of diabetes are known, genetics and lifestyle factors such as obesity and lack of exercise appear to play important roles. According to the American Diabetes Association (ADA), about 25 million people in the United States have diabetes. In addition, it is estimated that there are 54 million people in the United States who have pre-diabetes, a condition where blood glucose levels are higher than normal but not yet high enough to be diagnosed as diabetes.