There are two main types of fatigue: physical and mental.
A person with physical fatigue may find it physically hard to do the things they usually do, such as climbing the stairs. Symptoms include muscle weakness, and diagnosis may involve completing a strength test.
With mental fatigue, a person may find it harder to concentrate on things and stay focused. They may feel sleepy or have difficulty staying awake while working.
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) include weakness, lack of energy, constantly tired or exhausted, lack of motivation, difficulty concentrating, and/or 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 health care practitioner to discover the underlying cause(s) of the fatigue.