Chronic Fatigue Syndrome, also known as Myalgic Encephalomyelitis (CFS/ME), is a debilitating condition characterized by extreme, persistent fatigue that interferes with daily functioning and isn’t relieved by sleep. Additional symptoms often include cognitive dysfunction ("brain fog"), unrefreshing sleep, muscle pain, and post-exertional malaise (PEM), where even light activity can trigger days of worsening symptoms. Functional medicine investigates root causes such as mitochondrial dysfunction, viral reactivation (e.g. EBV), mold exposure, gut dysbiosis, and nutrient deficiencies. The goal is to restore energy production and reduce immune and inflammatory burdens using a personalized, step-by-step approach.