Fight fatigue by finding the cause

Kay Cahill Allison

Former Editor, Harvard Health

Feeling tired? If so, it’s not surprising. Fatigue is one of the most common problems people report to their doctors. The Health and Retirement Study of more than 17 million older people ages 51 and up reported recently that 31% said they feel fatigued.

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

Finding the cause. 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? For example, could you have chronic fatigue syndrome? That is an unusual illness and an uncommon cause of persistent fatigue, says Anthony Komaroff, M.D., professor of medicine at Harvard, world-renowned expert on chronic fatigue syndrome, and medical editor of a new Harvard Special Health Report, Boosting Your Energy. 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 chronic fatigue 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 syndrome.

If you feel unaccountably fatigued, make an appointment to see your doctor, especially 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 try to describe your symptoms in detail to help your doctor 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.

Medical conditions that cause fatigue. Once you’ve described your symptoms, your doctor may want to do some tests to rule out underlying causes listed here. Conditions that cause fatigue include:

  • Anemia
  • Congestive heart failure
  • Diabetes
  • Hypothyroidism
  • Infection
  • Kidney disease
  • Chronic fatigue syndrome
  • Depression and anxiety
  • Fibromyalgia


For more detail about how these conditions are linked to fatigue, read an excerpt from Harvard Medical School’s Special Health Report entitled Boosting Your Energy. This new Special Health Report offers information about the causes of fatigue and how it is linked to illness. No matter what the cause, there are lots of things you can do to try to get your old energy back. To help you do this, the report includes a step-by-step plan for boosting your energy naturally.


  1. Shay

    I believe fatigue is at all time high as an epidemic especially here in the U.S. due to diet and stress. Most folks seem to swallow down 4-hour energy drinks at 2pm. My wife had similar fatigue symptoms but found help simply eating more greens and less trash.


  2. Heather Smith

    This is again a great article,I did not know that fatigue is a symptoms of many diseases, thanks for listing it down, now I know that fatigue is a symptom and not a disease. Keep on posting.

  3. Oliver

    I’m doing some reseach for a new post on how to fall asleep. You’re definitely right, fatigue is a symptom and not a disease. But you CAN fight the symptoms, and I think you’re right again, that finding the cause is the single most important step in overcoming fatigue, just as finding the cause of chronic insomnia should be the first step to overcome sleeplessness.
    Thank you for a great article.

  4. Erik Johnson

    In a bizarre way, due to an unfortunate naming, the words “Chronic Fatigue Syndrome” are an uncannily accurate diagnostic tool. When spoken to someone that experienced the illness-entity which received this term, they are certain to say that the illness is not fatigue. Would someone that suspects they had a stroke allow a doctor to think they were merely sleepy? Anyone who is content to allow their illness to be conceived of as fatigue, has most certainly never experienced the neurological devastation that somehow managed to be named “Chronic Fatigue Syndrome”.

  5. sony

    fatigue can also be caused by the circumstances we are accustomed to lack of sleep or less istarahat, perhaps by prolonging the time of rest or sleep, it will create the conditions we will be slightly reduced fatigue.
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  6. Fatcat

    My chronic fatigue syndrome was absolutely caused by gluten. When I went gluten free my life was completely transformed. I no longer have to take a 3 hour nap every day. I also got rid of my daily headache.

  7. ebony

    I was looking for some Combat The Fat reviews and I got into this! You can even gain weight when you are stressed especially when you think about different problems! Yes, it’s best to learn how to manage stress!

  8. Jael

    Very well said. I really do admire almost all of your works. In relation to this topic, meditating is a good way to forgo the tension of a bad day. It keeps the mind healthy, and a healthy mind helps lead to a healthier body. Some people even use meditation as their primary resource for medical care, using the power of their minds instead of the power of medicine.

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  9. Dr Angela Miller

    Thank you for your informative article. In our practice we exhaust the commonly listed things you’ve clearly denoted then do a more exhaustive search measuring immunoglobulins, viral titer levels, vitamin levels and tests for autoimmunity. Thanks again!

  10. Dr. Judi

    Another very common cause of tiredness is sleep apnea.

  11. Cheryl Gajowski

    Article that is relevant to almost all of us! Also – lack of sleep – from apnea or the aggravating effects of menopause and beyond.

    Walter commented about lack of physical conditioning overall contributing to fatigue, which makes sense – but then you can get into And also, chicken-egg dilemma- which came first?
    Also, a related issue for me (and I’m not unique) – In rededicating myself – at 64 – to become more fit, I have found that adding muscle – a key to getting fit – is seriously difficult. I’d love an article dedicated to the science of strength -and balance – in aging folks. Not a cutesie article about the outliers running marathons at 95, but about what is happening, and whether there are any safe and useful supplements that can help the rest of us.

  12. Mary J Hetrick

    Please consider adding celiac disease to your list of medical conditions that cause fatigue.

  13. Rage

    Fatigue and other problems has many reasons behind there. Stress is the bigger and most common one. Need is to diagnosis your body and with the help of your physician try its natural cure as by Ayurveda and exercises treat it . They don’t make any side effect but a permanent relief for the disease.

  14. Ruth Stewart


    I used to find it very difficult to stay alert and unfatigued without sugar, so I would go from one sugar rush to the next all through the day. It did nothing for my waistline! Now I have completely cut sugar out of my diet which is occasionally hard going, but my energy is steady throughout the day. It is much easier for me since I have fibromyalgia.


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  15. Alfred Tanya

    Excelent review. I have alot of works to do, so i lack of rest. I only sleep for 2 or 3 hours everyday. I always go to my health practitioner near me.
    Is there any solution for my problem?
    Thanx for sharing
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  16. Justin Reilly, esq.

    Prof. Komaroff is a true stud!

    One of the few doctors or researchers willing to tell the truth about ME/CFIDS- that it is a debilitating neuro-immune disease. With more honest doctors like him the persecution of people with ME would end.

    I encourage Harvard to publish more on this common disease about which misinformation is the norm. According to CDC only 10% of ME patients are diagnosed. More education and coverage of ME would greatly improve public health. Thank you!

    • Janice Adams

      I have CFS (M.E) if anybody can help and offer some sound advice on what I can do to find the cause of my condition then please get in touch, I know excercise helps and pacing my life which can be boring because I use my energy to go to work sort the family then there is nothing left so have to go to the gym to get a slight recharge.

      Vitamins helathy diet all help however none of this gives me the root cause and I would like to understand my condition and how to get better soon. thanks to anybody who can help or know what is the best action.

  17. Cars Dublin

    I feel fatigue when I know I’m not eating correctly, sometimes it can be too many carbs but then sometimes if I’ve cut out my carbs I feel really tired too. I have made a conscious effort to balance all my food groups out to try and combat fatigue. I know my problems can also stem from lack of iron in my diet also.

  18. dean reinke

    In my case I have extreme fatigue as a result of a massive stroke. 3 years later during a physical I had a resting hearty rate of 54 at age 53 which puts me into the athlete category, my doctor asked me what cardiovascular exercises I was doing. None for the past three years. Fatigue is incredibly common in survivors with no explanations. I did find one idea, in normal use your brain uses 20% of your energy and while thinking hard can use quite a bit more energy. So every patient is on their own to find solutions.

  19. Nev Smith

    I have suffered from fatigue and was recommended CoQ10 by a pharmacist here in the UK and it certainly has worked for me, this is not some advert for them just sharing something that has worked for me.
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  20. KNW

    I’m a little disappointed that you did not note that fatigue is also a common symptom of several mental health diseases, such as depression.

  21. KokoArena

    Thank you for this wonderful post, so my first step to solving my fatigue problem is knowing the cause…there are really a lot of discussions online focusing on health but i think you guys are doing a good job here…

  22. Eric

    Thank you for your great work. You have yourself a follower all the way from Sweden 🙂

    Eric from Gothenburg, Sweden

  23. Patricia

    Thank you for another great article. I have had an overactive thyroid, and my father suffered from congestive heart failure. While I know I certainly need to get more sleep, I find that if I don’t drink tons of coffee, I am unable to stay awake. Even with drinking coffee, I struggle with fatigue everyday.

    In any event, I appreciate the article.

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  24. Jan Wiley

    Thank you, Dr. Komaroff, Editor Allison, and colleagues!

    ME/CFS since 1998

  25. ken hoover

    Why has no one done the research to correlate the link between fatigue and lack of physical conditioning? Strength, body composition, cardiovascular capacity, body composition, by the way in the case of higher numbers for women, this may reflect continued calorie restriction (dieting) and the subsequent loss of metabolic ability due to lean tissue loss that is known to result from calorie restriction, especially if we are “guessing” at numbers for calorie targets. I believe this is what is causing the numbers of obese, overweight, “Metabolic Disordered” to continue to rise. A failure to call it what it is. Lack of self discipline, self control and an understanding of how to create a hormonal environment that will allow for these conditions to improve. Increasing RMR and VO2 capacity would eliminate 90+% of “fatigue”.
    Is there really no widespread awareness that most of what people refer to as fatigue is simply less ability to perform work than work to perform. Why can we not remember that “it most likely is what it most likely is?

    • Walter

      This problem here is primarily one of nosology, accompanied by long-standing prejudice towards certain populations.

      If “Chronic Fatigue Syndrome” had been given a proper name, perhaps researchers would have been more interested in discovering the cause(s).

      For those who think that Chronic Fatigue is a symptom of poor conditioning and sedentary lifestyle, it would be helpful to study teenage athletes who come down with mono. They sleep. They’re fatigued. For some it takes months to recover. Their fatigue is not caused by poor conditioning or low VO2. Their fatigue is caused by the compound and cumulative damage caused by the Epstein-Barr virus. This virus penetrates the cell membrane, reproduces, and ultimately explodes out of the cell, killing it. If you’ve got this party going on in a few million cells for months on end, it will probably make you feel very bad. And fatigued.

      A substantial percentage of individuals diagnosed with “Chronic Fatigue” were previously healthy, well-conditioned adults. The onset varies but research suggests a small handful of viruses. In my case, the onset was mono. But I wasn’t a teenager. I was fifty-two. I lived on a boat, I swam every day, I was a free diver with enormous oxygen capacity. One night for about 15 minutes, I got the chills. A few weeks later I felt like I had an everyday virus. After a month I gave in and saw the doctor. I had mono. I never recovered.

      The “fatigue” part of this illness is not due to poor conditioning. It is due to the same biological processes which cause fatigue in anyone who has the flu, or mono, or any other number of systemic infections. Cell damage and destruction, along with taxation and disregulation of the immune system.

      I agree that there is most likely a growing population of obese individuals who are easily fatigued due to poor diet and conditioning. That kind of fatigue I imagine, is most likely “what it is.”

      Naming diseases and conditions is a rather subjective art. Some day, “Chronic Fatigue” will be renamed. Dr. Jose Montoya of Stanford has suggested “VICD” for viral-induced CNS dysfunction. Perhaps this is because Epstein-Barr and its cousins like to live in neural matter and CSF.

      I’m not a researcher or scientist. So I’m open to correction on any of my points.

      In the meantime, thank you Ms. Allison for your article!



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