When your body undergoes stress (such as adapting to fat burning or exercise) cortisol is released and/or adrenaline. This is to keep your blood sugar from going too low as it stimulates stored glucose release from the liver. Being a type 1 diabetic you do not produce the insulin needed to quickly drive the level of glucose back down. This is one of the truly sucky things about trying to emulate a pancreas with a needle. I am not a doctor though so take it for what it's worth.