Fatigue

Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a <a href="/facts/Signs_and_symptoms/BzP6MrTN">symptom</a> of any of various <a href="/facts/Disease/55eeQlGL">diseases</a>; it is not a disease in itself.
Fatigue (in the medical sense) is sometimes associated with medical conditions including <a href="/facts/Autoimmune_disease/sojBeQ7t">autoimmune disease</a>, <a href="/facts/Organ_failure/h5YCohyQ">organ failure</a>, <a href="/facts/Chronic_pain/o4rGTd95">chronic pain</a> conditions, <a href="/facts/Mood_disorder/Y0Mjq3QR">mood disorders</a>, <a href="/facts/Heart_disease/HD420nMv">heart disease</a>, <a href="/facts/Infectious_disease/182XrncP">infectious diseases</a>, and post-infectious-disease states. However, fatigue is complex and in up to a third of primary care cases no medical or psychiatric diagnosis is found.
Fatigue (in the general usage sense of normal tiredness) often follows prolonged physical or mental activity. Physical fatigue results from <a href="/facts/Muscle_fatigue/Qj71QeEW">muscle fatigue</a> brought about by intense <a href="/facts/Physical_activity/16Cmj4Kd">physical activity</a>. Mental fatigue results from prolonged periods of <a href="/facts/Cognition/ga0tSBul">cognitive</a> activity which impairs cognitive ability, can manifest as <a href="/facts/Sleepiness/mIlFhyf0">sleepiness</a>, <a href="/facts/Lethargy/wJFlYuB7">lethargy</a>, or <a href="/facts/Directed_attention_fatigue/urGlctSB">directed attention fatigue</a>, and can also impair physical performance.

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Fatigue