According to Diabetes Education Online, the liver acts as a reservoir by storing excess blood glucose until it is needed by the body. Hormones like insulin and glucagon signal the liver to begin storing blood sugar or releasing it, depending on the body's needs. In this way, the liver regulates how much glucose is in the bloodstream at any given time.
Before glucose can be stored in the cells of the liver, it has to be turned into glycogen. Insulin, a hormone secreted by the pancreas, aids in this process. Stored within the liver, these glycogen energy packages are turned back into glucose by the liver when energy is needed.
The body relies on the liver to produce energy in the form of glucose during fasts or periods where there is no food intake. For most people, this occurs on a regular basis, such as during the night or between meals. The liver starts creating glucose by transforming stored glycogen. When there is no glycogen present, the liver begins to harvest amino acids and fat to turn into glucose. When blood sugar levels are within normal range, the liver takes a break and waits for sugar levels to become high or low before stepping in again.