glucose /glo̅o̅″kōs/ [Gk, glykys, sweet] , a simple sugar found in certain foods, especially fruits, and a major source of energy present in the blood and animal body fluids. Glucose, when ingested or produced by the digestive hydrolysis of double sugars and starches, is absorbed into the blood from the intestines by a facilitated transport mechanism using carrier proteins. Excess glucose in circulation is normally polymerized within the liver and muscles as glycogen, which is hydrolyzed to glucose and liberated as needed. The determination of blood glucose levels is an important diagnostic test in diabetes and other disorders. Prepared glucose is a syrupy sweetening agent. Pharmaceutic preparations of glucose are widely used in the treatment of many disorders. Normal adult blood glucose levels range from 70 to 115 mg/dL (4 to 6 mmol/L), with generally higher levels after 50 years of age. See also dextrose, glycogen.