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Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

Steven Doerr, MD

Steven Doerr, MD

Steven Doerr, MD, is a U.S. board-certified Emergency Medicine Physician. Dr. Doerr received his undergraduate degree in Spanish from the University of Colorado at Boulder. He graduated with his Medical Degree from the University Of Colorado Health Sciences Center in Denver, Colorado in 1998 and completed his residency training in Emergency Medicine from Denver Health Medical Center in Denver, Colorado in 2002, where he also served as Chief Resident.

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The potential causes of fatigue are numerous. The majority of diseases known to man often list fatigue or malaise as possible associated symptoms. This is complicated by the fact that fatigue can occur in normal healthy individuals as a normal response to physical and mental exertion. However, normal fatigue may begin to become abnormal if it becomes chronic, extreme or prolonged fatigue; usually this occurs when a person experiences chronic or prolonged physical or mental exertion. For example, unusually hard physical or mental exertion for one day can result in normal fatigue that may last about a day or sometimes more, depending on the exertion level, while daily unusually hard physical or mental exertion may result in prolonged fatigue (usually greater than 24 to 48 hours). This latter situation may develop into abnormal fatigue.

The causes of fatigue can be classified under several broad disease entities or lifestyle problems that have fatigue as an associated symptom. The following table categorizes numerous causes of fatigue. This table is not meant to be all inclusive.

The following table summarizes some common causes of fatigue but is not meant to be comprehensive:

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