Finding the Cause of Fatigue, from Harvard Medical School’s Boosting Your Energy Special Health Report

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Fatigue is a common problem with many possible causes. Medical treatment or lifestyle changes can help alleviate fatigue once the cause is identified.

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Feeling tired? Fatigue is one of the most common problems people report to their doctors, according to Boosting Your Energy, a newly revised Special Health Report from Harvard Medical School. As many as 14% of men and 20% of women say they feel “frequently fatigued.”

Fatigue is a symptom, not a disease, and different people experience it in different ways. The fatigue you feel at the end of a long day or after a time zone change might feel similar to the fatigue resulting from an illness. But the difference is that fatigue from stress or lack of sleep usually subsides after a good night’s rest, while disease-related fatigue is more persistent and may be debilitating even after restful sleep.    

How do you know if your low-energy is caused by an underlying illness or is the result of stress, poor diet, or lack of sleep? Do you wonder if you have chronic fatigue syndrome?
Anthony Komaroff, M.D., Harvard’s world-renowned expert on chronic fatigue syndrome points out that it is an unusual illness, and an uncommon cause of persistent fatigue. Despite the high prevalence of fatigue, only about 4 to 8 of every 1,000 adults in the United States suffer from chronic fatigue syndrome which is about twice as common in women as in men. The causes of this syndrome are still unknown, and there is no accurate diagnostic test. However, scientists have found abnormalities in the brain and peripheral nervous system, in the immune system and in energy metabolism in people with this diagnosis.

It’s important to see your doctor if you feel so weary that you can’t do your regular activities as well or as often as you once did. Fatigue is a symptom of many illnesses, so describing your symptoms in detail can help narrow down the possible causes. How, exactly, does the fatigue feel to you? Do you have trouble concentrating? Does your body tire more quickly? Answers to these questions indicate how severe your fatigue is and whether it mainly involves muscle fatigue, brain fatigue, or both.

Once you’ve described your symptoms, your doctor may want to do some tests to rule out underlying causes. Conditions that include fatigue as a primary symptom include:

  • Anemia
  • Congestive heart failure
  • Diabetes
  • Hypothyroidism
  • Infection
  • Kidney disease
  • Chronic fatigue syndrome

If these conditions are ruled out, it’s good to know that there are lifestyle changes you can make that will help relieve fatigue from a variety of causes. The Harvard Special Health Report, Boosting Your Energy includes a step-by-step plan for boosting your energy naturally. Certain kinds of exercise have been shown to relieve fatigue. Sleep habits, diet, stress relief techniques, and other methods to alleviate fatigue are described in this report.

Also in this report:

  •     Aging and energy
  •     Finding the cause of fatigue
  •     When to see a doctor
  •     A 7-step plan to jump-start your natural energy

The Boosting Your Energy Special Health Report is available for $18 from Harvard Health Publications, the publishing division of Harvard Medical School. Order it online at or by calling 877–649–9457 (toll-free).

Media: Contact Raquel Schott at for a complimentary copy of the Special Health Report, or to receive our press releases directly.


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