Glycogen testing is a medical procedure used to measure the levels of glycogen stored in the body, particularly in the liver and muscles. Glycogen is a form of carbohydrate that serves as a key energy source during physical activity. This testing can help diagnose conditions related to glycogen metabolism, such as glycogen storage diseases. The process typically involves a biopsy, where a small sample of tissue is taken from the liver or muscle. The sample is then analyzed in a laboratory to determine glycogen content and structure. Results can provide valuable insights into metabolic health and guide treatment options.