What Is Fatigue?

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Fatigue is often described as a lack of energy and motivation—both physical and emotional. It is different than sleepiness or drowsiness, which describe the need for sleep. Fatigue is also a response to physical and mental activities. Normally, fatigue can be resolved with rest or reducing activity. Fatigue is a common complaint related to health issues. Notably, it is a symptom and not a specific disease or health condition. Many illnesses cause fatigue, and the symptoms can be physical, psychological, or a combination of both.

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According to a 2019 report in the journal Biological Research for Nursing, fatigue can be defined as an “overwhelming, debilitating, and sustained” exhaustion that makes it harder to carry out activities and function. Family practice physicians report that at least 20% of their patients report fatigue and up to 35% of adolescents report fatigue that occurs at least four days a week.

Men and women will describe fatigue differently. For example, men may say they are feeling tired, whereas women may report their fatigue as a feeling of anxiety or depression. People may also describe fatigue using a variety of terms, including feeling exhausted, weary, listless, or rundown.

People with fatigue experience one or more of three primary complaints. These vary person-to-person. They are:

  • Lack of motivation or the ability to start activities
  • Getting tired easily
  • Experiencing mental fatigue or problems with concentration or memory

Often, fatigue is a symptom with a gradual onset, meaning it comes on slowly and gets worse with time. Most people who experience fatigue may not be aware early on how much energy they are losing. They can only determine this when they try to compare their ability to perform tasks from one time frame to another.

Further, they may think fatigue is a common symptom—due to aging, being busy or overworked, not getting enough sleep, or a combination of all of these—and ignore the symptom. 

Don't ignore fatigue or delay seeking out medical care to determine the source of your fatigue. Your healthcare provider can help you pinpoint the cause and improve your quality of life.

Common Symptoms

Even though fatigue is a symptom of some underlying condition, it can still cause a combination of mental and physical symptoms, including:

  • Weakness
  • Lack of energy
  • Constant tiredness or exhaustion
  • Lack of motivation
  • Difficulty with concentration
  • Difficulty starting and completing tasks

Additional Symptoms

Fatigue is generally not a lone symptom. With it usually come other symptoms that can help your healthcare provider to determine the cause or causes of your fatigue.

Additional symptoms that may accompany fatigue include:

  • Headache
  • Dizziness
  • Sore, achy muscles
  • Muscle weakness
  • Slowed reflexes and response
  • Impaired judgment and decision-making
  • Moodiness, including irritability
  • Appetite loss
  • Impaired hand-to-eye coordination (the ability to do activities that require the use of both the hands, such as writing or driving)
  • Reduced immune system function
  • Attention difficulties and poor concentration
  • Memory problems
  • Blurry vision

Chronic Fatigue Syndrome

Fatigue is considered chronic when the feelings of exhaustion or lack of energy have lasted six or more months. Regardless of the cause, chronic fatigue will impact a person’s day-to-day functioning and quality of life.

A diagnosis of chronic fatigue syndrome (CFS) is made if a person has experienced chronic and ongoing fatigue for six months or more with no known cause, that is not improved with sleep or rest and that gets worse with physical or mental activity.

Symptoms of CFS can affect different parts of the body and may include unrefreshing sleep, weakness of muscles or joints, problems with memory and concentration, and headaches. Symptoms can be mild, moderate, or severe, and may come and go or last for weeks or months at a time. They can come on gradually or suddenly.


There are numerous potential causes of fatigue. For the majority of medical illness, fatigue is a possible symptom.

Normal fatigue—that is, fatigue that occurs from mental or physical exertion—is not unusual. However, normal fatigue can become abnormal if it becomes chronic (long-lasting) or severe.

Causes of chronic and severe fatigue can be anything from medical to lifestyle-related to stress (both work stress and emotional concerns).


Medical causes of fatigue may cause unrelenting exhaustion with additional symptoms. There are a number of diseases that trigger fatigue. If you find yourself experiencing long periods of fatigue, talk to your healthcare provider to determine the root cause.

The medical causes of fatigue can be classified under broad disease categories. Some of these disease categories are:

  • Metabolic / endocrine: Conditions such as, anemia, diabetes, hormonal imbalances, or liver or kidney disease
  • Infections: Influenza, tuberculosis, or malaria
  • Cardiac (heart) and pulmonary (lungs): Congestive heart failure, chronic obstructive pulmonary disease (COPD), arrhythmias, and asthma
  • Mental health: Depression and anxiety
  • Sleep problems: Sleep apnea, insomnia, and restless leg syndrome
  • Vitamin deficiencies: Vitamin D deficiency, vitamin B12 deficiency, or iron deficiency
  • Other conditions: Cancers and rheumatic/autoimmune diseases
  • Medications you are taking to treat other health conditions may also cause fatigue. This can include anti-depressants and anti-anxiety medications, sedative medication, some blood pressure medications, chemotherapy, radiation therapy, and steroids.


Lifestyle causes tend to be related to sleep disturbances, diet, lack of regular exercise, the use of alcohol or drugs, or other factors.

Sleep disturbances: If you are not getting enough sleep, too much sleep, or waking up during the night, you may experience daytime fatigue.

Diet: If you are eating a lot of high-carb, high-fat, or quick-fix foods, sugary foods and drinks, or caffeinated drinks, you are not providing your body enough fuel or nutrients to function at its best. Moreover, these foods may cause you to experience energy boosts that quickly wear off, leading to a "crash" and worsening fatigue.

Alcohol and drugs: Alcohol is a depressant that will slow down the nervous system and disturb sleep. Cigarettes and caffeine will stimulate the nervous system and cause you trouble with falling asleep and staying asleep.

Lack of regular activity: Physical activity is known for improving your health and well-being, reducing stress, and improving your energy levels. It will also help you sleep better and reduce daytime fatigue.

Individual factors: Personal or family illness or injury, having too many commitments, and financial problems can cause a person to feel fatigued.


Stress causes can be related to a stressful work environment, toxic relationships, or mental health problems, such as depression and anxiety.

Workplace-related fatigue: People who work night shifts may experience daytime fatigue. This is because the human body is designed to sleep at night, and a person who works the night shift confuses the body’s circadian clock. Poor workplace practices, such as irregular working hours, physical labor, long hours, noisy workplaces, fixed concentration, and repetitive tasks also contribute to fatigue. Burnout and other workplace stressors, such as a heavy workload, conflict with bosses or coworkers, workplace bullying, or threats to job security can all be contributors to fatigue.

Mental health: Depression, anxiety, and grief can all lead to fatigue. These conditions exhaust the body physically and emotionally and cause severe fatigue to set in.


Fatigue presents with a range of symptoms and is often caused by a number of different factors working in combination. That makes finding a diagnosis more difficult. Therefore, your healthcare provider will try to determine what is causing fatigue using a number of tests, including the following.

Medical history: Your healthcare provider will ask about recent stressful (good and bad) events in your life, such as the birth of a child, surgery, work stress and family problems, or other symptoms you have experienced in addition to fatigue.

Physical exam: A physical exam will help your practitioner check for signs of disease. Your medical professional may also ask about your current diet and lifestyle.

Testing: Tests can include blood work, urine screens, X-rays, and other imaging. Your healthcare provider will want to rule out physical causes.

When to See a Healthcare Provider

You should see your healthcare provider if your fatigue:

  • Has come on suddenly and is not the result of normal short-term physical or mental stress   
  • Is not relieved with rest, sleep, or removal of stressors
  • Has become severe or chronic
  • Is accompanied by other unexplained symptoms
  • Associated with weakness, fainting, or near fainting
  • Is accompanied with unexplained weight loss, masses or lumps anywhere on the body, fever (greater than 101 degrees Fahrenheit), abnormal vaginal bleeding, and/or unexplained pain anywhere in the body

Signs of a Medical Emergency

Go to your local hospital emergency department if you experience the following symptoms, with or without fatigue:

  • Fainting
  • Chest pain
  • Shortness of breath
  • Bleeding (e.g., vomiting blood or rectal bleeding)
  • Severe abdominal, pelvic, or back pain
  • Severe headache
  • Irregular or fast heart rate


Treatment for fatigue depends on the causes. Some treatments for conditions that cause fatigue include medications, vitamins, diet, exercise, and avoiding unhealthy habits such as smoking, using drugs, or drinking alcohol in excess.

Fortunately, many of the causes of fatigue are treatable. For example, anemia can be treated with iron supplements, sleep apnea can be treated with medicine and CPAP machines, medications can maintain blood sugar and blood pressure, antibiotics can treat infections, and vitamins can regulate vitamin deficiencies.

There are also a number of things you can to lessen fatigue caused by daily activity and boost energy levels and overall health. These include:

  • Staying hydrated
  • Eating healthy foods
  • Exercising regularly
  • Getting enough sleep
  • Avoiding known stressors
  • Avoiding over-demanding work and social schedules
  • Practicing relaxation activities, such as yoga

Lifestyle changes are helpful in easing fatigue, but it is also important to follow your healthcare provider’s treatment plan for any diagnosed medical condition. Left untreated, fatigue can negatively affect your physical and mental health.

A Word From Verywell 

The prognosis for fatigue is generally good, because many of the causes are easy to treat. However, the prognosis varies based on the cause, underlying conditions, and your overall health.

While you can manage fatigue, you probably cannot prevent its many causes. Therefore, it is important to recognize when fatigue is a problem in order to seek appropriate medical care and a prompt diagnosis.

Sometimes, fatigue is a gradual symptom and is difficult to figure out. If family and friends bring to your attention gradual declines in your ability to be as active as you used to be, don't dismiss this information; bring it to your healthcare provider's attention. Self-awareness of gradual decline in health is sometimes missed because people make small accommodations to compensate, and therefore may miss developing problems. 

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Matura LA, Malone S, Jamie-Lara R, et al. A Systematic Review of Biological Mechanisms of Fatigue in Chronic Illness. Biol Res Nurs. 2018 Jul;20(4): 410–421. doi:10.1177/1099800418764326

  2. Rothenthal TC, Majeroni BA, Pretorius R, et al. Fatigue: An Overview. Am Fam Physician; 78(10):1173-1179.

  3. Office of Women’s Health. Chronic Fatigue Syndrome

Additional Reading

By Lana Barhum
Lana Barhum has been a freelance medical writer since 2009. She shares advice on living well with chronic disease.