The causes of low energy can fill a medical textbook. Almost every chronic illness is associated with low energy. There are some easily fixable causes such as anemia and low thyroid. Severe fatigue not related to a diagnosable illness may be an illness in itself called Chronic Fatigue Syndrome in the U.S. or Myalgic Encephalomylitis in England, Canada and Australia. There may be deficiencies of vitamins, minerals and amino acids which can be assessed through blood and urine tests. Correcting these deficiences can improve energy for many people. There may be impairments of the immune system from viruses, bacteria or toxic metals or chemicals which can be evaluated and treated. The course of recovery is highly individual and is based on many environmental and genetic factors. The CDC has recently established the validity of Chronic Fatigue as a specific illness through extensive genetic studies.