Fatigue is a medical symptom that can be caused by a variety of reasons. It is regarded as a symptom, and not as a medical sign, because it is experienced by the patient as opposed to being noticed by others. There are two types of fatigue: physical fatigue and mental fatigue. Physical fatigue refers to the incapacity of the muscles to use force that can be usually exerted by the person. Mental fatigue on the other hand refers to a diminished level of concentration with accompanying somnolence.

Following the two types of fatigue, the major causes of it are musculoskeletal and psychological. Some of the common activities and experiences that induces fatigue are overworking, mental stress, overstimulation and understimulation, jet lag, active recreation, depression, boredom, some diseases, and lack of sleep. Fatigue can also be caused by chemicals vitamin and mineral deficiencies and poisoning. Fatigue can also be caused by massive blood loss.

While fatigue can be a body response to physical exertion and stress, it can also be a symptom of an underlying medical condition. Temporary fatigue is a normal body behavior after the immune system fights an infection. Chronic fatigue, something that is experienced for at least 6 months, on the other hand is usually an indication of a serious disease.

Some of the conditions that have chronic fatigue as a symptom include autoimmune diseases, blood disorders, cancer, depression, eating disorders, endocrine diseases, fibromyalgia, heart disease, infectious diseases, leukemia, neurological disorders, pain-causing conditions like arthritis, pregnancy, sleep disorders, uremia, and hepatic failure. Some medications can also cause fatigue such as lithium salts, ciprofloxacin, beta blockers, chemotherapy, and radiotheraphy. Also, a rare condition called chronic fatigue syndrome can also cause chronic fatigue. It is currently unknown what causes this condition and therefore it can only be diagnosed after ruling out the other possible conditions. This is somewhat difficult as chronic fatigue syndrome shares many symptoms with other conditions, namely fibromyalgia, autoimmune diseases, and depression.

It is therefore important for those who experience prolonged fatigue to seriously consider consulting a professional about their condition as it may cause serious implications in one’s health.