High blood sugar means having too much sugar, also called glucose, in the blood. High blood sugar is also called hyperglycemia. The body’s cells need blood sugar. A normal blood sugar level is 70 to 100. A blood sugar level above 140 is too high. You may not feel any signs of high blood sugar but damage may be happening to your body. Over time, high blood sugar can damage the eyes, kidneys, blood vessels, heart, nerves and feet.