The liver both stores and produces glucose

The liver acts as the body’s glucose (or fuel) reservoir, and helps to keep your circulating blood glucose levels and other body fuels steady and constant. The liver both stores and manufactures glucose depending upon the body’s need. The need to store or release glucose is primarily signaled by the hormones insulin and glucagon. During a meal, your liver will store glucose, as glycogen for a later time when your body needs it. The high levels of insulin and suppressed levels of glucagon during a meal promote the storage of glucose as glycogen.

The liver makes glucose when you need it

When you’re not eating – especially overnight or between meals, the body has to make its own glucose. The liver supplies glucose by turning glycogen into glucose in a process called glycogenolysis. The liver also can manufacture necessary glucose by harvesting amino acids, waste products and fat byproducts. This process is called gluconeogenesis. The liver also makes another fuel, ketones, when glucose is in short supply. When your body’s glycogen storage is running low, the body starts to conserve the glucose supplies for the organs that always require glucose. These include: the brain, red blood cells and parts of the kidney. To supplement the limited glucose supply, the liver makes alternative fuels called ketones from fats. This process is called ketogenesis. The hormone signal for ketogenesis to begin is a low level of insulin. Ketones are burned as fuel by muscle and other body organs. And the glucose is saved for the organs that need it. 

It is important for individuals with Diabetes to understand these concepts, because some of the high morning blood glucoses commonly seen in Diabetes are a result of excessive gluconeogenesis overnight. Too much ketone formation is a less common problem, but can be dangerous, and needs emergency medical attention.