What Is Chronic Fatigue? Symptoms And Treatments

December 18, 2023
A tired women drinking coffee and using a computer

Chronic fatigue syndrome (CFS) is a challenging condition for the people who have it and the medical professionals and researchers who are trying to understand it. CFS, also known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), is an illness with an uncertain cause that frequently causes serious disability. According to the Institute of Medicine, approximately 836,000 to 2.5 million Americans live with ME/CFS. Up to 84% to 91% of people who meet the diagnostic criteria are not yet diagnosed.1

Many people find medical conditions without objective findings even more challenging to deal with. A person with this condition can be managing debilitating symptoms that are not visible to others.

Many people with this condition, more commonly women than men, describe it as bone-deep, unrelenting fatigue that does not improve with sleep. The symptoms can worsen with physical or mental activity, which makes working, engaging in family life, and attending to activities of daily living difficult.

What Is Myalgic Encephalomyelitis/Chronic Fatigue?

Chronic fatigue syndrome is a serious, chronic disease that affects many body systems, causing symptom constellations that vary from person to person. Researchers have identified physiologic changes in the nervous, endocrine, and immune systems and changes in energy metabolism but have not yet identified a clear understanding of how these changes cause disease.2,3

There have been many definitions for ME/CFS, and they have evolved over time.2 The Institute of Medicine (National Academy of Sciences) proposed the following diagnostic criteria for ME/CFS:

  • A substantial reduction or impairment in the ability to engage in occupational, educational, social, or personal activities in the same way as pre-illness.
  • Symptoms persist for at least six months.
  • Fatigue that is profound and new-onset, not lifelong, and is not the result of excessive exertion.
  • Fatigue is not relieved by rest.
  • Malaise after exercise.
  • Unrefreshing sleep.
  • Either cognitive impairment or orthostatic intolerance.

ME/CFS is more common in women than in men. It can affect people of any age but is more common in people aged 40 to 60.

A woman with neck pain

Symptoms Of Chronic Fatigue 

People may experience ME/CFS slightly differently, and their symptoms may come and go. However, some symptoms are more consistently found, including the following:

  • New onset, overwhelming fatigue: This level of fatigue keeps you from participating in family, social, and work life. It is unrelenting fatigue that is not relieved by rest or sleep. It is completely normal for people to experience fatigue with illness, lack of sleep, or after strenuous exertion. This is more than that. It is fatigue after minimal physical or mental activity.
  • Unrefreshing sleep: Everyone has difficulty sleeping sometimes. With ME/CFS, people sleep more than normal, but the sleep is unrefreshing. They wake just as tired as when they went to sleep.
  • Cognitive Impairment: Sometimes called “brain fog,” cognitive impairment is changes in memory and difficulty processing information, concentrating, and multitasking. Information processing may slow, making it hard to think, reason, calculate, and multitask. People describe brain fog in different ways, but it usually includes memory impairment, difficulty concentrating, and a change in your ability to think.
  • Orthostatic intolerance: Symptoms commonly worsen when sitting or standing and improve when lying down. Common orthostatic symptoms are feeling lightheaded, weak, or dizzy.
  • Pain: While not a required symptom to meet the definition of MF/CFS, pain is a common symptom, including muscle aches, nerve pain, headaches, numbness, and joint pain.

Chronic Fatigue Syndrome Vs. Natural Energy Loss 

Chronic fatigue syndrome causes an overwhelming sense of fatigue that does not improve with sleep, exercise intolerance, and fatigue with mental effort. Chronic fatigue syndrome typically has an abrupt start. Previously healthy people experience a sudden change in their health.

Natural energy loss is normal fatigue that may be associated with increased exercise, lack of sleep, medication use, aging, weight changes, and chronic disease. Most people with natural energy loss are able to go about their day and meet their family, social and work obligations (though it may be challenging).

Unlike people with MF/CFS, people with natural energy loss can usually come up with solutions to improve their energy and motivation.

Here are some common causes of natural energy loss and ways to reduce fatigue associated with it.

  • Aging: Lack of exercise, poor diet, changes in body composition, chronic disease, and medication use can all cause an increase in fatigue with age. Many people, including researchers, are seeing aging as a chronic disease. This may seem counterintuitive since we all age, but when aging becomes considered a disease, the amount of research on age management will increase exponentially. We are already seeing new research in possible ways to slow aging.
  • Excessive exercise or exertion: Strenuous exercise can cause fatigue. Rest days are important to allow your body time to repair damaged muscle tissue, metabolize waste and restore energy stores.
  • Medications: Several medications cause fatigue as a side effect. Antihistamines are a good example. Next-generation antihistamines do not cause quite the fatigue that the older-generation ones did, but many people still need to choose between fatigue from allergies and fatigue from medications.
  • Chronic disease: MF/CFS is not the only chronic disease that causes fatigue. Several of the autoimmune, cardiovascular, neurologic, and respiratory disorders do as well.
A tired older woman using a computer

When To Talk To Your Doctor About Chronic Fatigue

Many people who meet the definition of MF/CFS remain undiagnosed. While MF/CFS does not have a specific diagnostic lab test or biomarker, the constellation of symptoms provides evidence of the condition. MF/CFS symptoms overlap with many other conditions. See your doctor to rule out some of these more easily diagnosed conditions and for guidance on how to best manage your MF/CFS symptoms.

Since MF/CFS is currently diagnosed based on having symptoms consistent with the condition for at least six months, it is important to keep track of your symptoms. A symptom diary can help your doctor make a diagnosis and rule out other conditions.

Possible Comorbidities Of Chronic Fatigue 

Researchers have identified abnormalities in the nervous, endocrine, and immune systems associated with ME/CFS. Several other conditions share similar physiologic abnormalities and may overlap or be comorbid with ME/CFS.


Fibromyalgia is a chronic condition characterized by chronic widespread muscle pain with tender points. It may also cause sleep disturbances, joint stiffness, mood disorders, cognitive impairment, and digestive symptoms. Like ME/CFS, the causes of fibromyalgia are not understood, and the condition can be difficult to diagnose.4

Myofascial Pain Syndrome 

Myofascial pain syndrome is also characterized by trigger points, but the pain is more localized. The condition affects muscles and the connective tissue that surrounds them. The trigger points that cause pain in myofascial pain syndrome originate in the fascia, a thin layer of connective tissue that wraps muscle.

Myofascial pain syndrome is most commonly diagnosed in middle-aged women and affects the head and neck muscles. Unlike fibromyalgia, the pain does not occur throughout the body, but like fibromyalgia, the underlying cause is not fully understood, making it difficult to diagnose and treat.

Irritable Bowel Syndrome

Irritable bowel syndrome is a functional gastrointestinal disorder. It causes abdominal pain, cramping, bloating, constipation, and diarrhea. Like these other conditions, the underlying physiology of irritable bowel syndrome is not well understood. It is a chronic condition for which there is no highly effective treatment.

Treatment Options For Chronic Fatigue

ME/CFS and its comorbid conditions are poorly understood, have no accepted diagnostic test, and are not easily treated. According to the American Myalgic Encephalomyelitis and Chronic Fatigue Syndrome Society, these are the best treatment/management options:

  • Avoid allergens and chemicals
  • Medications available:
    • Sleep: over the counter and prescription sleep aids
    • Pain: over-the-counter and prescription pain medications that may decrease nerve sensitivity
    • Orthostatic symptoms: Electrolyte solutions and prescription medications that may reduce dizziness and lightheadedness with position changes
    • Cognitive dysfunction: piracetam and stimulants to reduce cognitive dysfunction
    • Antimicrobials: infections may trigger symptoms
  • Supplements:
    • Antioxidants such as glutathione, alpha lipoic acid, vitamins E and C
    • Essential fatty acids: Omega-3, fish oil, and flaxseed oil
  • Others: pacing, exercise, stress reduction, acupuncture, and biofeedback

If you have ME/CFS and try some of these treatment/management options, go slow and try them one at a time. Keep a record of how you feel and any changes in your symptoms.

What Is Chronic Fatigue? Symptoms And Treatments
Author: Leann Poston, M.D.
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  • Prins JB, van der Meer JW, Bleijenberg G. Chronic fatigue syndrome. Lancet. 2006 Jan 28;367(9507):346-55. doi: 10.1016/S0140-6736(06)68073-2. PMID: 16443043.
  • Gluckman, S. (2022). Clinical features and diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome.
  • Rowe PC, Underhill RA, Friedman KJ, et al. Myalgic encephalomyelitis/chronic fatigue syndrome diagnosis and management in young people: A primer. Front Pediatr. 2017;5:121. doi:10.3389/fped.2017.00121
  • Bellato E, Marini E, Castoldi F, et al. Fibromyalgia syndrome: Etiology, pathogenesis, diagnosis, and treatment. Pain Res Treat. 2012;426130. doi:10.1155/2012/426130
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