Glucose is a vital energy source for cells and levels in the blood stream must remain constant. The liver helps maintain blood glucose levels in response to the pancreatic hormones insulin and glucagon.
After a meal, glucose enters the liver and levels of blood glucose rise. This excess glucose is dealt with by glycogenesis in which the liver converts glucose into glycogen for storage. The glucose that is not stored is used to produce energy by a process called glycolysis. This occurs in every cell in the body.
In between meals or during starvation, blood glucose levels fall. The hepatocytes detect this change, and restore glucose levels by either glycogenolysis which converts glycogen back to glucose, or gluconeogenesis in which non-sugars such as amino-acids are converted to glucose.