Callistemon 'I don't know a lot about T1 diabetes but have a couple of friends with that condition and they carry sweets with them in case they need them.'
It's because Type 1 diabetics inject insulin. In a non-diabetic body, the pancreas produces just the right amount of insulin for the food eaten/to maintain the level of glucose in the blood. When you inject insulin, it's a fixed amount, calculated by you, and there are all sorts of things that can make your blood glucose levels too low (not enough carb in a meal, exercise, stress, alcohol, etc. etc.). If you go too low you risk going into a coma and death, so a quick snack of sweet food can avert this.