Type 1 diabetes is the type of diabetes mellitus where the immune system destroys the insulin-producing beta cells of the pancreas, leaving the body able to make little or no insulin. Without insulin, glucose cannot enter cells and accumulates in the blood. It typically appears in childhood or young adulthood, though adult onset occurs, and its cause is autoimmune rather than lifestyle. Management is lifelong: injected or pumped insulin matched to carbohydrate intake, blood glucose monitoring, and attention to diet, exercise, and illness. It is distinct from the far more common type 2 diabetes. With modern insulins and monitoring technology, people with type 1 diabetes live full, healthy lives.