You can often lower your blood glucose level by exercising. However, if your blood glucose is above 240 mg/dl, check your urine for ketones. If you have ketones, do not exercise.
Exercising when ketones are present may make your blood glucose level go even higher. You'll need to work with your doctor to find the safest way for you to lower your blood glucose level.
Cutting down on the amount of food you eat might also help. Work with your dietitian to make changes in your meal plan. If exercise and changes in your diet don't work, your doctor may change the amount of your medication or insulin or possibly the timing of when you take it.