Alternative names: Exhaustion, unrelenting exhaustion, lingering tiredness, constant lack of energy, excess fatigue, ongoing fatigue, weariness, lethargy, listlessness, feeling run down
Fatigue can be described as a lack of energy and motivation – either physical, mental, or both. It is a term used to describe an overall feeling of tiredness and/or a lack of energy.
It is quite normal to feel tired sometimes, but unexplained, persistent, relapsing exhaustion indicates an underlying problem.
The onset of fatigue is often very gradual, so much so that we may not be aware of it until we compare our ability to function with how we used to function several months or years ago. We may assume that it is simply a natural consequence of aging, and ignore it for this reason.
Fatigue is an extremely common symptom. It is not a disease in itself.
There are hundreds of possible causes of fatigue, falling into these broad categories:
In about one-third of patients the cause of fatigue is never found.
Fatigue (either mental, physical, or both) is a symptom that may be difficult for a patient to describe. Words such as lethargic, exhausted and tired are often used. The characteristics of excess fatigue include:
Fatigue is usually due to something 'obvious', although at first the connection may not seem obvious. Examples of 'obvious' causes include lack of exercise, lack of sleep, jet lag, drug side-effects, or depression. Once these have been ruled out, other possible causes – of which there are hundreds, both benign and serious – should be considered.
Treatment depends on the underlying cause. Because diagnosis can take some time, there are things that can be done in the meantime to relieve the fatigue to some extent.
One study found that all those subjected to carb-free diet complained of fatigue after just two days. "This complaint was characterized by a feeling of physical lack of energy... The subjects all felt that they did not have sufficient energy to continue normal activity after the third day. This fatigue promptly disappeared after the addition of carbohydrate to the diet." [Arch Internal med 112(1963): p.333]
Being just 5% dehydrated can lead to fatigue due to decreased blood volume and a reduced supply of oxygen and nutrients to the brain and muscles.
A British study of 71 healthy volunteers aged 21 to 76 found that a daily 30 minute program of yogic stretching and breathing exercises had an invigorating effect on mental and physical energy and mood.
Fatigue can be one of the most debilitating symptoms experienced by people with HIV disease, as well as one of the most under-reported and under-recognized aspects. The rate of fatigue increases as the disease progresses and women are more likely to experience fatigue than men. HIV-positive men with CD4 cell counts below 500 cells/ml experienced more fatigue than men with CD4 cell counts above 500. However, studies so far have not found a consistent correlation between viral load and fatigue. The fatigue may be due to anemia, depression, the HIV virus, secondary infections, hormone deficiency (testosterone, adrenal exhaustion), malnutrition, poor sleep quality or quantity, inactivity, or drug side-effects.
Depression robs the brain of some of the chemicals needed for optimal function. Serotonin, for example, helps regulate the internal body clock. Depression can lead to decreased energy levels and daytime tiredness, as well as difficulty falling asleep at night. It can also cause us to wake up earlier in the morning than we had planned.
As nephrotic syndrome progresses, the patient feels increasingly weak and fatigued.
In individuals with sleep apnea, the brain detects that they are not getting rid of enough CO₂, so it wakes up briefly in an alarmed state. This happens repeatedly during the night, without the subject noticing, and results in an inability to achieve or maintain the deep stages of sleep. This can lead to unexplained daytime sleepiness and nonrestorative sleep. Patients often complain of waking up feeling like they had not slept at all, and often feel worse after taking a nap than before napping.
People who have less body weight to carry around generally have much more energy for activities.
Your body is a highly complex, interconnected system. Instead of guessing at what might be wrong, let us help you discover what is really going on inside your body based on the many clues it is giving.
Our multiple symptom checker provides in-depth health analysis by The Analyst™ with full explanations, recommendations and (optionally) doctors available for case review and answering your specific questions.