Chronic fatigue syndrome (CFS) is a complicated disorder with an unknown cause.  CFS is characterized by persistent fatigue that does not improve with rest and that cannot be explained by any identifiable medical condition.

CFS is also known as myalgic encephalomyelitis (ME) and systemic exertion intolerance disease (SEID).  It is sometimes abbreviated ME/CFS.

CFS patients typically have low levels of Coenzyme Q10 in their blood and tissues.  Some studies have shown that CoQ10 supplementation improves the symptoms of CFS.