Fatigue

=== By timescale ===

==== Acute ====
Acute fatigue is that which is temporary and self-limited. Acute fatigue is most often caused by an [[infection]] such as the [[common cold]] and can be cognized as one part of the [[sickness behavior]] response occurring when the [[immune system]] fights an [[infection]].<ref name="Brain, Behavior, and Immunity 2012 pp. 552–558">{{cite journal |last1=Piraino |first1=B. |last2=Vollmer-Conna |first2=U. |last3=Lloyd |first3=A.R. |title=Genetic associations of fatigue and other symptom domains of the acute sickness response to infection |journal=Brain, Behavior, and Immunity |date=May 2012 |volume=26 |issue=4 |pages=552–558 |doi=10.1016/j.bbi.2011.12.009 |pmid=22227623 |pmc=7127134 }}</ref>

Other common causes of acute fatigue include [[Major depressive disorder|depression]] and chemical causes, such as [[dehydration]], [[poison]]ing, [[low blood sugar]], or [[Mineral (nutrient)|mineral]] or [[vitamin]] deficiencies.

==== Prolonged ====
Prolonged fatigue is a self-reported, persistent (constant) fatigue lasting at least one month.<ref name="pmid34589772">{{cite journal |vauthors=Billones R, Liwang JK, Butler K, Graves L, Saligan LN |title=Dissecting the fatigue experience: A scoping review of fatigue definitions, dimensions, and measures in non-oncologic medical conditions |journal=Brain Behav Immun Health |volume=15 |issue= |pages=100266 |date=August 2021 |pmid=34589772 |pmc=8474156 |doi=10.1016/j.bbih.2021.100266 |url=}}</ref><ref name="pmid18458765">{{cite journal |vauthors=Griffith JP, Zarrouf FA |title=A systematic review of chronic fatigue syndrome: don't assume it's depression |journal=Prim Care Companion J Clin Psychiatry |volume=10 |issue=2 |pages=120–8 |date=2008 |pmid=18458765 |pmc=2292451 |doi=10.4088/pcc.v10n0206 }}</ref>

==== Chronic ====
Chronic fatigue is a self-reported fatigue lasting at least 6 consecutive months. Chronic fatigue may be either persistent or relapsing.<ref name="CDC1994">{{cite journal | vauthors = Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A | title = The chronic fatigue syndrome: a comprehensive approach to its definition and study. International Chronic Fatigue Syndrome Study Group | journal = Annals of Internal Medicine | volume = 121 | issue = 12 | pages = 953–959 | date = December 1994 | pmid = 7978722 | doi = 10.7326/0003-4819-121-12-199412150-00009 | author-link2 = Stephen Straus | s2cid = 510735 | author-link = Keiji Fukuda | author-link6 = Anthony L. Komaroff }}</ref> Chronic fatigue is a symptom of many chronic illnesses and of [[idiopathic chronic fatigue]].{{medical citation needed|date=July 2023}}