Can I exercise any time I want?

Ask your health care team about the best time of day for you to exercise. Consider your daily schedule, your meal plan, and your diabetes medications in deciding when to exercise.

If you exercise when your blood glucose is above 300, your level can go even higher. It's best not to exercise until your blood glucose is lower. Also, exercise is not recommended if your fasting blood glucose is above 250 and you have ketones in your urine. For information about preventing or treating low blood glucose, see Can physical activity cause low blood glucose?

source: http://diabetes.niddk.nih.gov/dm/pubs/physical_ez/index.htm