What happens if a child does not take care of their juvinal diabetes?

Sickness and death. Untreated juvenile diabetes will cause death. Partially treated (or poorly treated) diabetes will lead to long term complications like blindness, kidney failure, heart disease, strokes, amputations, and early death.
DKA. If a child doesn't take care of his diabetis, he will go into dka, which is acute diabetic crisis due to high blood sugar. It produces acid in the blood and causes vomiting and abdominal pain.