Chronic fatigue syndrome is a chronic illness marked by severe fatigue, cognitive difficulties, and pain. It is estimated to affect approximately 1 in 100 people, but many people remain undiagnosed due to its unclear cause and varying symptoms.

Chronic fatigue syndrome is characterized by severe fatigue that does not improve with rest, along with symptoms such as sleep disturbances, difficulty concentrating, pain, dizziness, gastrointestinal discomfort, and postexertional malaise. These symptoms can be unpredictable and may fluctuate in severity over time.

Chronic fatigue syndrome is diagnosed primarily by identifying its characteristic signs and symptoms because there are no definitive tests for the condition. Diagnosis also involves ruling out other potential conditions such as hypothyroidism, anemia, lupus erythematosus, and cancer.

There are no direct medical treatments for chronic fatigue syndrome; instead, treatments focus on managing symptoms. Options include medications for sleep issues, cognitive problems, and pain, although not all symptoms have effective treatments.

Although many supplements show potential for chronic fatigue syndrome, high-quality research is lacking. The most promising supplements include magnesium, L-carnitine, and S-adenosyl methionine; others, like probiotics and NADH, possibly alleviate symptoms but do not improve the condition itself.

Diet may affect chronic fatigue syndrome; people with gastrointestinal discomfort might try to avoid ultraprocessed foods and experiment with eliminating potentially problematic foods like caffeine, alcohol, spicy foods, dairy, and gluten; however, there is limited direct evidence to associate ultraprocessed foods with chronic fatigue syndrome.

People with chronic fatigue syndrome should pace themselves to avoid worsening symptoms and can explore various symptom-oriented treatments, including meditation, light therapy, behavioral changes, physical therapy, massage, acupuncture, and neurofeedback, though effectiveness may vary.

The cause of chronic fatigue syndrome remains a matter of debate, but it is generally considered a neurological condition due to observed changes in cognition, such as slower information processing and reduced working memory. However, chronic fatigue syndrome does not have distinct characteristic signs.