Two of the most common signs of high blood sugar are constant thirst and the need to urinate frequently. When you have high blood sugar, your kidneys have to work harder to filter your blood.herefore, it is important to keep your blood sugar in a healthy range through good diet and exercise. If you have one or more of the following symptoms, it may be time to schedule an appointment with your doctor to have your blood sugar checked. 7 Signs of High Blood Sugar.