Diabetes occurs when the glucose, or sugar, in the blood is poorly controlled and consistently high.
Type 1 occurs when the body does not produce enough of the hormone that allows cells to absorb and use glucose. This hormone is called insulin.
While a person can prevent type 2 by avoiding a sugar-rich diet and inactive lifestyle, preventing type 1 is not possible. The immune system attacks clusters of cells in the pancreas that would normally produce insulin, called islets, stopping or slowing insulin production.
Without enough insulin, glucose cannot enter the cells and remains in the bloodstream.
A person with type 1 diabetes will need to take insulin for the rest of their life. Not doing so can result in ever-increasing blood sugar levels and dangerous complications.
Type 1 diabetes can occur at any age, although it is more common in children and young adults.