Fatigue: Causes

By McBratney, Susan PhD

What causes fatigue?

Fatigue can be caused by a wide variety of diseases, disorders or conditions, such as anemia, low blood pressure (hypotension), chronic fatigue syndrome, and Addison's disease. Although fatigue can be due to relatively mild and temporary conditions, such as jet lag, fatigue can also be caused by serious or life-threatening conditions, such as organ failure or cancer.

Fatigue that lasts for more than six months, is not alleviated by rest, and is not due to a known mental or physical illness is defined as chronic fatigue syndrome (CFS). The cause of CFS is not known at this time.

Common causes of fatigue

Fatigue can be due to common conditions including:

  • Allergies that cause hay fever or asthma

  • Anemia

  • Chronic pain

  • Dehydration

  • Depression

  • Endocrine abnormality (thyroid, adrenal gland, etc.)
  • Fever

  • Hyperthyroidism (overactive thyroid gland) or hypothyroidism (underactive thyroid gland)

  • Jet lag

  • Perimenopause (the period of time close to menopause) and menopause

  • Pregnancy

  • Sleep problems such as obstructive sleep apnea and insomnia

Other causes of fatigue

Fatigue can be due to a variety of other diseases, disorders and conditions including:

  • Addison’s disease (deceased production of hormones by the adrenal glands)

  • Cancer

  • Chronic fatigue syndrome

  • Chronic obstructive pulmonary disease (COPD, includes emphysema and chronic bronchitis)

  • Congestive heart failure

  • Diabetes (chronic disease that affects your body’s ability to use sugar for energy)

  • Fibromyalgia (syndrome associated with long-term, body-wide pain points)

  • Infectious diseases, such as HIV/AIDS, influenza and infectious mononucleosis

  • Liver or kidney disease

  • Myasthenia gravis (autoimmune neuromuscular disorder that causes muscle weakness)

  • Rheumatoid arthritis and osteoarthritis

  • Systemic lupus erythematosus or other connective tissue disorders

  • Toxic environmental exposure

Medications that can cause fatigue

Always tell your doctor about any medications or supplements you are taking, including prescription and over-the-counter medications and herbal or alternative supplements. The following medications may be a possible cause of fatigue:

  • Antidepressants

  • Antihistamines

  • High blood pressure medications or diuretics

  • Sleeping medications, tranquilizers, sedatives, and anti-anxiety medications

  • Steroids

Questions for diagnosing the cause of fatigue

To diagnose the underlying cause of fatigue, your doctor or licensed health care practitioner will ask you several questions related to your symptoms. You can best help your health care practitioner in diagnosing the underlying cause of fatigue by providing complete answers to these questions:

  • Describe the fatigue. Is it constant or intermittent? Is it mild, moderate or severe? Does it occur with or after certain activities or events, such as stress, exercise, or just before the menstrual period?

  • How long have you had fatigue?

  • What other symptoms do you have with fatigue?

What are the potential complications of fatigue?

Complications associated with fatigue can be progressive. It is important to visit your health care provider promptly when you experience unexplained fatigue. Once the underlying cause is diagnosed, following the treatment plan you and your health care provider design specifically for you can help reduce potential complications including:

  • Decreased overall quality of life
  • Depression

  • Inability to perform daily tasks and disability

  • Malnutrition from loss of appetite associated with fatigue

  • Poor quality of life


  1. Fatigue. Medline Plus, a service of the National Library of Medicine National Institutes of Health.  http://www.nlm.nih.gov/medlineplus/ency/article/003088.htm.
  2. Chronic fatigue syndrome (CFS). Centers for Disease Control and Prevention. http://www.cdc.gov/cfs/general/index.html.
  3. Tierney LM Jr., Saint S, Whooley MA (Eds.) Current Essentials of Medicine (4th ed.). New York: McGraw-Hill, 2011.
  4. Ricci JA, Chee E, Lorandeau AL, Berger J. Fatigue in the U.S. workforce: prevalence and implications for lost productive work time. J Occup Environ Med 2007; 49:1.

What is fatigue?

Fatigue is a feeling or sensation of tiredness, weariness, exhaustion, weakness or low energy that occurs during or after routine activities. Fatigue can also be a feeling of inadequate energy to begin such activities. Fatigue is a symptom of a wide variety of mild to serious diseases, disorders and conditions including infection, inflammation, trauma, malignancy, chronic diseases, autoimm... Read more about fatigueintroduction


What other symptoms might occur with fatigue?

Fatigue may occur with other symptoms that vary depending on the underlying disease, disorder or condition. For example, fatigue caused by hypothyroidism may be associated with dry, brittle hair, hair loss, unusual weight gain, and possibly goiter (neck swelling due to enlargement of the thyroid gland). Fatigue associated with Read more about fatiguesymptoms

Medical Reviewer: William C. Lloyd III, MD, FACS Last Annual Review Date: Aug 9, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

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