Type 1 diabetes in the past was often referred to as juvenile or insulin-dependent diabetes. In this type of diabetes, the pancreas is no longer able to produce insulin - the hormone that allows sugar (glucose) to enter body cells. This is the result of destruction of the insulin-producing cells of the pancreas, known as beta cells.
Without enough insulin, glucose builds up in the bloodstream instead of going into the cells. The body is unable to use this glucose for energy despite high levels in the bloodstream. This leads to increased hunger.
In addition, the high levels of glucose in the blood causes increased urination, and thus, excessive thirst. Within several years of presentation, the insulin-producing beta cells of the pancreas are completely destroyed and the body can no longer produce insulin.
Type 1 diabetes can occur at any age. However, half of the patients are diagnosed before the age of 20. The exact cause is unknown. Genetics, viruses, and environmental factors are thought to play a role in causing the autoimmune response that eventually leads to beta cell destruction.