A blood glucose level of 339 mg/dL or above attained from either the Fasting Plasma (FPG) or Random Glucose Tests generally indicates extreme hyperglycemia. Hyperglycemia is a condition that occurs when the body doesn't have enough insulin. Consistent blood sugar levels of 339 mg/dL or higher indicate a high risk for diabetes. You should consult with your physician immediately, and make sure to check your urine for ketones before exercising.
Learn more about hyperglycemia and diabetes.