Type 1 diabetes is an autoimmune disease in which the immune system mistakenly attacks the insulin-producing beta cells in the pancreas. Without these beta cells, the body cannot maintain proper blood glucose levels in response to daily activities such as eating or exercise. With fewer insulin producing cells blood glucose increases, causing hunger, thirst, and unexplained weight loss. By the time these symptoms develop, 80-90% of a person's beta cells have already been destroyed. However, this also means that between 10-20% of these cells remain that continue to produce insulin.