Do you know the cause for type 1 diabetes
There is no known cause for Type 1 Diabetes. It is possible that genetics play a part (for instance, if it runs in your family you will have a higher % chance of getting it) however there is no known reason.
The beta cells of the pancreas are unable to produce insulin causing the blood to be saturated with sugar/glucose. Outside insulin must be injected for the body to store excess glucose as glycogen.