Type 1 diabetes is a rare autoimmune disease in which the body’s immune system attacks and destroys cells in the pancreas that make insulin. Without insulin, your body loses its capacity to control blood sugar. Type 2 diabetes is more common than Type 1 diabetes. With Type 2 diabetes, the body may still make insulin, but it loses its ability to use it. For different reasons, Type 1 and Type 2 diabetes both lead to high blood glucose.