I am a type one diabetic and have been for almost 23 years now. I am on an insulin pump. I'm sure everyone has different signs for themselves, but i can tell you from my own experience some of them.
Low blood sugar
can't walk straight
High blood sugar
flu like symptoms
possibly throwing ketones in urine
I'm sure that doesn't cover all of the possibilities, but that is how I feel if my blood is out of whack. Hope that helps you some. Any other questions, just ask. If I know, I'll answer