fatigue

Fatigue is a subjective sense of tiredness, exhaustion, or lack of energy that is not relieved by rest and that reduces a person’s ability to perform usual activities. It is distinct from sleepiness, which results from inadequate or poor-quality sleep, and from generalized weakness due to illness. Fatigue can be acute, lasting hours to days, or chronic, lasting weeks to months.

Fatigue can be physical, mental, or both. Physical fatigue presents as reduced strength and endurance, slower movement, and leg heaviness. Mental fatigue involves difficulties with concentration, memory, and decision-making. Chronic fatigue may be part of a specific medical condition or a syndrome when no cause is found after evaluation.

Common causes include medical illnesses such as infections, anemia, thyroid disorders, diabetes, kidney or liver disease, and heart failure. Sleep disorders (insomnia, sleep apnea), mental health conditions (depression, anxiety), medications, and lifestyle factors (stress, poor sleep hygiene, sedentary behavior, poor nutrition, alcohol use) are frequent contributors. Rarely, persistent fatigue may be part of chronic fatigue syndrome, a prolonged and disabling fatigue lasting at least six months with accompanying symptoms.

Diagnosis relies on history, physical examination, and targeted tests to identify reversible conditions. Blood tests commonly involve complete blood count, ferritin, thyroid-stimulating hormone, glucose, and kidney and liver function; additional tests may be guided by symptoms. Evaluation for sleep disorders, mood disorders, and medication effects is also important.

Management focuses on treating any underlying condition and implementing nonpharmacologic strategies: good sleep hygiene, regular physical activity, balanced nutrition, hydration, stress management, and energy-conservation techniques. Pharmacologic treatment is used for specific causes (e.g., anemia, thyroid disease). Prognosis varies; fatigue may improve with treatment of underlying conditions, though some cases persist, particularly in chronic fatigue syndrome. Seek medical assessment for persistent or worsening fatigue, especially with weight loss, fever, chest pain, or cognitive changes.