Hyperglycemia refers to high levels of sugar, or glucose, in the blood. It occurs when the body does not produce or use enough insulin, which is a hormone that absorbs glucose into cells for use as energy. High blood sugar is a leading indicator of diabetes.  Hyperglycemia means high (hyper) glucose (gly) in the blood (emia). ... Hyperglycemia is a defining characteristic of diabetes—when the blood glucose level is too high because the body isn't properly using or doesn't make the hormone insulin. Eating too many processed foods may cause your blood sugar to rise.