Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link
Some Common Causes and Features of Prolonged or Chronic Fatigue

Some Common Causes and Features of Prolonged or Chronic Fatigue


Common Features*


Blood disorders or cancers

Decreased exercise tolerance with shortness of breath during activity greater than expected for the activity

Sometimes paleness


Widespread lymph node swelling, weight loss, and night sweats

With multiple myeloma, low back or other bone pain, often severe at night



Sometimes jaundice, loss of appetite, and fluid in the abdomen

Blood tests to determine how well the liver is functioning and to identify the hepatitis virus

Sometimes liver biopsy


Sometimes cough and respiratory symptoms

Sometimes loss of taste and smell

Blood test for SARS-CoV-2

Enlarged spleen and lymph nodes, fever, and night sweats

Sometimes blood tests for antibodies to cytomegalovirus

Fever and night sweats

Sometimes joint pains

Usually in people who have heart murmurs or inject drugs intravenously

Cultures of blood samples and echocardiography

Fever, night sweats, and frequent infections

Sometimes difficulty breathing, cough, diarrhea, and/or rash

HIV blood test

Recent sore throat and lymph node swelling

Mononucleosis blood test

Fever, night sweats, and weight loss

Sometimes cough, difficulty breathing, and coughing up blood

Tests based on which type of infection seems likely

Other disorders and causes

Shortness of breath, difficulty breathing when lying down that is relieved when upright (orthopnea), and/or swelling

Blood tests of kidney function

Fever, night sweats, weight loss, joint pain, rash, and/or other organ involvement (for example, effects on the heart or lungs)

Blood tests for abnormal antibodies


A history of lack of exercise or being bedbound or hospitalized

Only a doctor's examination

Excessive thirst, excessive urination, increased appetite, and unexplained weight gain or loss

Measurement of sugar (glucose) level in the blood after the person fasts overnight and sometimes glucose tolerance testing

Drugs: Antidepressants, older antihistamines, antihypertensives, diuretics that cause low potassium levels in the blood, muscle relaxants, recreational drugs, and sedatives

History of taking a drug known to cause fatigue

Only a doctor's examination

Headache, pain in the jaw when chewing, pain when combing hair, loss of vision, and/or muscle pains in a person over 50

ESR and temporal artery biopsy

Anxiety, sadness, loss of appetite, and unexplained sleep disturbance

With somatization disorder, an excessive preoccupation with physical symptoms

Only a doctor's examination

Fatigue worse with exposure to heat

Past symptoms of nervous system malfunction (such as numbness, loss of coordination, and weakness), particularly if people had more than one episode of symptoms

Brain and/or spinal cord MRI


Cessation of menstrual periods, breast tenderness, morning sickness, and abdominal swelling

Pregnancy test

Sleep laboratory testing (polysomnography)

Inability to tolerate cold, weight gain, constipation, and coarse skin

Blood tests of thyroid function

Weight loss

Sometimes loss of appetite, foul-smelling stool, abdominal pain, or a combination

A doctor's examination

Sometimes other tests

Disorders of unknown cause

Sore throat, sleep that is not refreshing, difficulty with concentration or short-term memory, muscle aches, joint pain, headaches, and/or tender lymph nodes in the neck or under the arms

Only a doctor's examination

Long-standing and widespread muscle and bone pain in areas outside the joints, trigger points, lower abdominal pain, gas, bloating, constipation or diarrhea, migraines, and anxiety

Only a doctor's examination

* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

CBC = complete blood count; ESR = erythrocyte sedimentation rate; HIV = human immunodeficiency virus; MRI = magnetic resonance imaging.