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.
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.
Fatigue is generally defined as a feeling of lack of energy and motivation
that can be physical, mental or both. Fatigue is not the same as drowsiness, but
the desire to sleep may accompany fatigue. Apathy is a feeling of indifference
that may accompany fatigue or exist independently. In addition, individuals
often describe fatigue using a variety of terms including weary, tired,
exhausted, malaise, listless, lack of energy and feeling run down.
Fatigue is common. About 20% of Americans claim to have fatigue intense
enough to interfere with living a normal life. A physical cause has been
estimated to be responsible 20% to 60% of the time, while emotional or mental causes
comprise the other 40% to 80% of cases of fatigue. Unfortunately, fatigue can also occur in
normal individuals that experience intense physical or mental activity (or
However, in contrast to fatigue that occurs with some diseases and
syndromes, normal fatigue in healthy individuals is quickly relieved in a few
hours to about a day when the physical or mental activity is reduced. Also,
people occasionally experience fatigue after eating (sometimes termed
postprandial depression) which can be a normal response to food, especially
after large meals and this may last about 30 minutes to several hours.
In addition to the many terms attributed to "fatigue", there are further
problems with the terminology used to describe fatigue. There are several
"fatigue syndromes" that occasionally appear in the medical literature. For
example, Epstein-Barr chronic fatigue syndrome, post viral infection fatigue
syndrome, and adrenal fatigue syndrome are among the most commonly seen. However,
many physicians do not recognize these as syndromes because the criteria used to
define them as syndromes are too diffuse and many consider the associated
fatigue (sometimes chronic fatigue) as either a symptom or complication of the
underlying associated diseases. However, there is a well-defined
syndrome recognized by specific criteria. Basically, two
sets of criteria need to be met to establish a diagnosis of chronic fatigue
1. Have severe chronic fatigue for at least six months or longer with other
known medical conditions (whose manifestation includes fatigue) excluded by
clinical diagnosis; and
2. Concurrently have four or more of the following symptoms:
Consequently, people and their health care practitioners need to spend some time
together to clearly determine whether or not the problem or symptom is truly
fatigue, and if it is, any associated symptoms that may accompany the fatigue
should be explored.
There are numerous potential causes of fatigue as a major complaint. They range from those that cause poor blood supply to the body's tissues to illnesses that affect metabolism, from infections and inflammatory diseases to those that cause sleep disturbances. Fatigue is a common side effect of many medications.
Some common cause of fatigue include:
metabolic or endocrine disorders
(anemia, thyroid, diabetes, etc.);