Depression and other psychological conditions can produce fatigue, so people who report fatigue are routinely screened for these conditions, along with substance use disorders, poor diet, and lack of physical exercise, which paradoxically increases fatigue. Basic medical tests may be performed to rule out common causes of fatigue. These include blood tests to check for infection or anemia, a urinalysis to look for signs of liver disease or diabetes mellitus, and other tests to check for kidney and liver function, such as a comprehensive metabolic panel. Other tests may be chosen depending on the patients social history, such as an HIV test or pregnancy test. Comparison with sleepiness
Fatigue is generally considered a more long-term condition than sleepiness (somnolence). Although sleepiness can be a symptom of a medical condition, it usually results from lack of restful sleep, or a lack of stimulation. Chronic fatigue, on the other hand, is a symptom of a greater medical problem in most cases. It manifests in mental or physical weariness and inability to complete tasks at normal performance. Both are often used interchangeably and even categorized under the description of being tired. Fatigue is often described as an uncomfortable tiredness, whereas sleepiness is comfortable and inviting. Measurement
Fatigue can be quantitatively measured. Devices to measure medical fatigue have been developed by Japanese companies, among them Nintendo (cancelled). Nevertheless, such devices are not in common use outside Japan.
Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve after rest or sleep, or occurs independently of physical or mental exertion, it may be a symptom of a medical condition that may become severe or progressive.Fatigue can be a feature of a mental disorder such as depression; may be associated with conditions of chronic pain such as fibromyalgia; it may also feature in conditions of chronic low-level inflammation, and be a disease-related symptom in many other conditions. Fatigue often has no known cause, and is recognised as being very complex in nature. Fatigability describes a susceptibility to fatigue.Physical fatigue results from muscle fatigue brought about by intense physical activity. Mental fatigue results from prolonged periods of cognitive activity which impairs cognitive ability. Mental fatigue can manifest as sleepiness, lethargy, or directed attention fatigue. Mental fatigue can also impair physical performance. Classification
Physical
Physical fatigue, or muscle fatigue, is the temporary physical inability of muscles to perform optimally. The onset of muscle fatigue during physical activity is gradual, and depends upon an individuals level of physical fitness – other factors include sleep deprivation and overall health. Physical fatigue can be caused by a lack of energy in the muscle, by a decrease of the efficiency of the neuromuscular junction or by a reduction of the drive originating from the central nervous system, and can be reversed by rest.