Your blood sugar level is an essential measure for your health. You have to learn how to monitor it and to make it part of your daily routine. Your doctor or a diabetes educator can help you with this.
An appropriate diet and some physical activity can help you lower your blood glucose level.
But there are special cases as well. If you have a high level of blood sugar you may check for ketones in your urine. If you have ketones you should not exercise. This may cause the opposite effect.
If you think you have hyperglycemia contact your doctor.
More info on hyperglycemia can be found here.