Reviewed on 11/14/2022

What Should I Know About Fatigue?

Picture of Common Causes of Chronic Fatique Syndrome
Picture of Common Causes of Chronic Fatique Syndrome

What Is the Definition of Fatigue?

Fatigue is generally defined as a feeling of lack of energy and motivation that can be physical, mental, or both. Fatigue is not the same as drowsiness, but the desire to sleep may accompany the fatigue. Apathy is a feeling of indifference that may accompany fatigue or exist independently. In addition, individuals often describe fatigue using a variety of terms including weary, tired, exhausted, malaise, listless, lack of energy, and feeling run down.

How Common Is Fatigue?

Fatigue is common. About 20% of Americans claim to have fatigue intense enough to interfere with living a normal life. A physical cause has been estimated to be responsible for 20% to 60% of the time, while emotional or mental causes comprise the other 40% to 80% of cases of fatigue. Unfortunately, fatigue can occur in normal individuals who experience intense physical or mental activity (or both).

However, in contrast to fatigue that occurs with some diseases and syndromes, normal fatigue in healthy individuals is quickly relieved in a few hours to about a day when the physical or mental activity is reduced. Also, people occasionally experience fatigue after eating (sometimes termed postprandial depression), which can be a normal response to food, especially after large meals and this may last about 30 minutes to several hours.

In addition to the many terms attributed to "fatigue," there are further problems with the terminology used to describe fatigue. There are several "fatigue syndromes" that occasionally appear in the medical literature. For example, Epstein-Barr chronic fatigue syndrome, post-viral infection fatigue syndrome, and adrenal fatigue syndrome are among the most commonly seen. However, many physicians do not recognize these as syndromes because the criteria used to define them as syndromes are too diffuse and many consider the associated fatigue (sometimes chronic fatigue) as either a symptom or complication of the underlying associated diseases. However, there is a well-defined chronic fatigue syndrome recognized by specific criteria. Basically, two sets of criteria need to be met to establish a diagnosis of chronic fatigue syndrome:

  1. Have severe chronic fatigue for at least 6 months or longer with other known medical conditions (whose manifestation includes fatigue) excluded by clinical diagnosis; and
  2. Concurrently have four or more of the following symptoms:

Consequently, people and their healthcare professionals need to spend some time together to clearly determine whether or not the problem or symptom is truly fatigue, and if it is, any associated symptoms that may accompany the fatigue should be explored.

What Are the Signs and Symptoms Associated With Fatigue?

Fatigue is a symptom that usually has some underlying cause. Fatigue may be described by people in different ways, and may include some combination (both mental and physical) of:

  • Weakness
  • Lack of energy
  • Constantly feeling tired or exhausted
  • Lack of motivation
  • Difficulty concentrating
  • Difficulty starting and completing tasks

Other symptoms such as fainting or loss of consciousness (syncope), near-syncope, rapid heartbeat (palpitations), dizziness, or vertigo may also be described as part of the fatigue experienced by the affected individual. The presence of these symptoms may actually help lead a healthcare practitioner to discover the underlying cause(s) of the fatigue.

When Should You Call a Doctor for Fatigue?

Generally, people need to seek medical care if they experience any of these symptoms. Fatigue that:

  • Comes on suddenly (not due to normal short-term physical or mental stress)
  • Is not relieved by adequate rest, adequate sleep, or removal of stressful factors
  • Becomes chronic or extreme
  • Is accompanied by unexplained symptoms
  • Is associated with fainting or nearly fainting

If a person experiences any of the following with or without associated fatigue, they should go to the emergency department:

Additional symptoms that are often associated with fatigue and require urgent medical treatment include:

What Causes Fatigue?

The potential causes of fatigue are numerous. The majority of diseases often list fatigue or malaise as possible associated symptoms. This is complicated by the fact that fatigue can occur in normal healthy individuals as a normal response to physical and mental exertion.

However, normal fatigue may begin to become abnormal if it becomes chronic, extreme, or prolonged fatigue; usually, this occurs when a person experiences chronic or prolonged physical or mental exertion. For example, unusually hard physical or mental exertion for one day can result in normal fatigue that may last about a day or sometimes more, depending on the exertion level, while daily unusually hard physical or mental exertion may result in prolonged fatigue (usually greater than 24 to 48 hours). This latter situation may develop into abnormal fatigue.

The causes of fatigue can be classified under several broad disease entities or lifestyle problems that have fatigue as an associated symptom. Some common causes of fatigue that are not meant to be comprehensive include:

What Exams, Procedures, and Tests Diagnose the Cause of Fatigue?

Medical History

For the evaluation of fatigue, the health care practitioner will take a complete history of the patient's fatigue, along with questions in regard to associated symptoms. The healthcare practitioner may inquire about the following activities and symptoms to determine the probable cause of the fatigue:

  • Does the level of fatigue remain constant throughout the day?
  • Does the fatigue get worse as the day goes on, or does the fatigue begin at the start of the day?
  • Is there a pattern of fatigue (time of day or time of year like the holidays)?
  • Does the fatigue occur at regular cycles?
  • How is the person's emotional state?
  • Does the person feel unhappiness or disappointment in life?
  • How much sleep is the person getting?
  • During what hours does the person sleep?
  • Does the person wake up feeling refreshed or fatigued?
  • How many times does the person awake during sleep?
  • Are they able to fall back asleep?
  • Does the person get regular exercise? Any exercise?
  • Has the person had any new stressors in their life? Change in relationships, jobs, school, or living arrangements?
  • What is the person's diet?
  • Is there a high intake of coffee, sugar, or excessive amounts of food?

Associated symptoms (not all-inclusive as answers may trigger other questions) may include fever, pain, nausea, vomiting, diarrhea, blood in urine or stool, shortness of breath, chest pain, constipation, muscle cramps or aches, easy bruising, cough, changes in thirst or urination, inability to sleep lying flat, inability to walk up more than one flight of stairs, changes in appetite, loss or gain of weight, menstrual irregularities, swollen legs, and/or mass in the breast.

Physical Exam

After obtaining a medical history, a physical exam will be performed, focusing on the patient's vital signs (weight, blood pressure, heart rate, temperature, and breathing rate). The doctor will observe the patient's general appearance, listen to the heart, lungs, and abdomen, and may perform a pelvic and rectal exam. The doctor may order some of the following tests depending on the suspected underlying cause of the fatigue.

  • Blood tests provide information about infections, anemia, other blood abnormalities, or problems with nutrition.
  • Urinalysis provides information that might point to diabetes, liver disease, or infection.
  • Chem-7 looks at 7 common substances circulating in the blood. It consists of electrolytes (sodium, potassium, chloride, and bicarbonate), waste products of metabolism cleared by normally functioning kidneys (BUN and creatinine), and the source of energy for the body's cells (glucose).
  • Thyroid function tests examine the function of the thyroid gland (thyroid levels too high or too low).
  • Pregnancy tests check for pregnancy.
  • Sedimentation rate test checks for chronic diseases or inflammatory conditions.
  • HIV test check for HIV infection.
  • Chest X-ray explores the possibility of infections or tumors.
  • Electrocardiogram (EKG) is an electrical recording that looks at the function of the heart.
  • CT scan of the head is a 3-dimensional X-ray of the brain to look for stroke, tumors, or other abnormalities.

The definitive diagnosis depends on discovering the underlying cause of the fatigue; this is determined by evaluating the history, the physical exam, and the appropriate test results.

What is the Treatment for Fatigue?

The treatment for fatigue depends upon the cause. Some treatments for conditions that cause fatigue include medications, antibiotics, vitamins, and exercise.

Medical treatment of fatigue depends on the treatment of its underlying cause(s). Fortunately, many causes of fatigue may be treated with medications, for example:

  • Iron supplements for anemia
  • Machines to help with sleep apnea
  • Medications to control blood sugar
  • Medications to regulate thyroid function
  • Antibiotics to treat infection
  • Vitamins
  • Recommendations for dietary changes
  • A sensible exercise program

Again, treatment of the underlying cause(s) is the key to the treatment of the symptom of fatigue.

What Is the Prognosis for Fatigue? Can It Be Cured?

Generally, the prognosis for fatigue is good, because many of the causes are relatively easy to treat. However, the prognosis decreases if the person has difficulty in complying with treatments or has underlying conditions (for example, advanced diabetes or COPD) that are severe and slowly progress.

How Can You Prevent Fatigue?

Fatigue prevention (both physical and mental) is possible in many people. Prevention of the underlying cause in almost every situation will prevent the symptom of fatigue:

  • Manage stress and practice relaxation techniques.
  • Get exercise, but begin slowly and check with your healthcare practitioner before beginning any exercise program. Find a good time to exercise and develop a habit of exercise.
  • Check your medications with a health care practitioner or pharmacist to see if some medications could be responsible for fatigue.
  • Improve your diet and eat a good breakfast (whole grain cereal, fruit, milk). Add more fruits and vegetables.
  • Stop any excessive caffeine consumption.
  • Stop smoking.
  • Have sex with your spouse or partner.
  • Get enough sleep and have a good and consistent sleep routine (sleep hygiene). Go to bed at the same time every night.
  • Avoid coffee, tea, or caffeinated drinks after 6 pm.
  • Do not drink alcohol after dinner, and decrease the total amount of alcohol consumed. (Alcohol interferes with sleep patterns.)
  • People with underlying medical conditions (for example, diabetes, COPD, and anxiety) can reduce symptoms of their disease, including fatigue, by working with their healthcare practitioners to optimize the treatment of the underlying problems.
Women with Chronic Fatigue Syndrome

What Is Chronic Fatigue Syndrome (CFS)?

Chronic fatigue syndrome (also called CFS) is a disorder without a known cause, although CFS may be related to a previous infection. CFS is a state of chronic fatigue that exists without other explanation for six months or more and is accompanied by cognitive difficulties (problems with short-term memory or concentration). You may have CFS if you meet the following criteria:

  • if you have severe chronic fatigue for six months or longer and all other known conditions that could cause fatigue have been excluded by your health-care provider, or
  • if you simultaneously have four or more of the following symptoms: significant problems with short-term memory or concentration, sore throat, tender lymph nodes, muscle pain, pain in several joints without swelling or redness, headaches that are different in pattern or severity from previous headaches, feeling tired and unrefreshed even after sleeping, and extreme tiredness lasting more than 24 hours after you exercise or exert yourself.
Reviewed on 11/14/2022
Centers for Disease Control and Prevention. Chronic Fatigue Syndrome (CFS).

Davis, MP, Walsh, D. Mechanisms of fatigue. J. Support. Oncol., 8:164-174, 2010>