Muscles use insulin during exercise and then glucose to be pulled from the bloodstream to use for energy lowering the amount of glucose circulating in the blood stream. Here are a couple articles that can help you decide how best to prepare for exercise to be sure you don't fall into a situation where your glucose levels falls to an unsafe level during exercise.
Exercising with Type 2 Diabetes
Manage Glucose, Lose Weight, and Reduce Complications www.sparkpeople.com/resource/fitness_artic
Carbohydrate Adjustments for Exercisers with Diabetes
What to Look for Before You Exercise www.sparkpeople.com/resource/fitness_artic
Hope that helps.