What is Exhaustion?
Fatigue is a normal result of working, mental stress, overstimulation and understimulation, jet lag or active recreation, depression, and also boredom, disease and lack of sleep. It may also have chemical causes, such as poisoning or mineral or vitamin deficiencies. Massive blood loss frequently results in fatigue. Fatigue is different from drowsiness, where a patient feels that sleep is required. Fatigue is a normal response to physical exertion or stress, but can also be a sign of a physical disorder.

Temporary fatigue is likely to be a minor illness like the common cold as one part of the sickness behavior response that happens when the immune system fights an infection.

Prolonged fatigue is defined as fatigue persisting for at least one month. Chronic fatigue is defined as fatigue persisting for at least six consecutive months. Chronic fatigue may be either persistent or relapsing. Chronic fatigue is a non-specific symptom.