Glycogen is stored mainly in the liver, but the skeletal muscles and glial cells in the brain also contain a small amount of glycogen. The amount of glycogen stored in the liver is about 10 percent of its mass.
Although the amount of glycogen stored in muscles is only about 1 percent of their mass, muscle tissue contains about twice the amount of glycogen that the liver does because the amount of muscle mass in the body surpasses the mass of the liver.
Glucose, a major source of bodily fuel, is stored in the form of glycogen. Excess glucose can be converted into glycogen, the storage form of glucose in animals. When the body senses a need for more glucose, the hormone glucagon is released and acts on the liver to convert glycogen back to glucose for use.