View source for Dehydration

{{Short description|Deficit of total body water}}
{{Distinguish|hypovolemia}}
{{About|excessive loss of human body water}}
{{Use mdy dates|date=September 2015}}
{{cs1 config|name-list-style=vanc|display-authors=6}}
{{Infobox medical condition (new)
| name = Dehydration
| synonyms = 
| image = Cholera rehydration nurses.jpg
| alt = 
| caption = Nurses encourage a patient to drink an oral rehydration solution to treat dehydration caused by [[cholera]].
| pronounce = 
| field = [[Critical care medicine]]
| symptoms = Increased [[thirst]], tiredness, decreased urine, [[dizziness]], headaches, and confusion<ref name=MY6 />
| complications = Low blood volume shock ([[hypovolemic shock]]), [[coma]], [[seizures]], [[urinary tract infection]], [[kidney disease]], [[heatstroke]], [[hypernatremia]], [[metabolic disease]],<ref name=MY6>{{cite web  |title=Dehydration - Symptoms and causes | publisher=Mayo Clinic |url=https://www.mayoclinic.org/diseases-conditions/dehydration/symptoms-causes/syc-20354086#:~:text=Dehydration%20occurs%20when%20you%20use,fluids%2C%20you%20will%20get%20dehydrated}}</ref> [[hypertension]]<ref name="El-Sharkawy_2015">{{cite journal | vauthors = El-Sharkawy AM, Sahota O, Lobo DN | title = Acute and chronic effects of hydration status on health | journal = Nutrition Reviews | volume = 73 | issue = Suppl 2 | pages = 97–109 | date = September 2015 | pmid = 26290295 | doi = 10.1093/nutrit/nuv038 }}</ref>
| onset = 
| duration = 
| types = 
| causes = Loss of body water
| risks = [[Physical water scarcity]], [[heatwaves]], [[disease]] (most commonly from diseases that cause [[vomiting]] and/or [[diarrhea]]), [[exercise]]
| diagnosis = 
| differential = 
| prevention = 
| treatment = Drinking clean water
| medication = [[Saline (medicine)|Saline]]
| prognosis = 
| frequency = 
| deaths = 
}}
In physiology, '''dehydration''' is a lack of total [[body water]] that disrupts [[Metabolism|metabolic processes]].<ref name="Mange K 1997">{{cite journal | vauthors = Mange K, Matsuura D, Cizman B, Soto H, Ziyadeh FN, Goldfarb S, Neilson EG | title = Language guiding therapy: the case of dehydration versus volume depletion | journal = Annals of Internal Medicine | volume = 127 | issue = 9 | pages = 848–853 | date = November 1997 | pmid = 9382413 | doi = 10.7326/0003-4819-127-9-199711010-00020 | s2cid = 29854540 }}</ref> It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild dehydration can also be caused by [[immersion diuresis]], which may increase risk of [[decompression sickness]] in [[Underwater diving|divers]].

Most people can tolerate a 3–4% decrease in total body water without difficulty or adverse health effects. A 5–8% decrease can cause [[fatigue]] and [[dizziness]]. Loss of over 10% of total body water can cause physical and mental deterioration, accompanied by severe [[thirst]]. [[Death]] occurs with a 15 and 25% loss of body water.<ref name=Ashcroft>Ashcroft F, Life Without Water in Life at the Extremes. Berkeley and Los Angeles, 2000, 134-138.</ref> Mild dehydration usually resolves with [[Oral rehydration therapy|oral rehydration]], but severe cases may need intravenous fluids.

Dehydration can cause [[hypernatremia]] (high levels of [[sodium ions]] in the blood). This is distinct from [[hypovolemia]] (loss of [[blood volume]], particularly [[blood plasma]]).

Chronic dehydration can cause [[kidney stones]] as well as the development of [[chronic kidney disease]].<ref>{{Cite book | vauthors = Seal AD, Suh HG, Jansen LT, Summers LG, Kavouras SA |chapter=Hydration and Health | chapter-url = https://linkinghub.elsevier.com/retrieve/pii/B9780128145562000117 | veditors = Pounis G |title=Analysis in Nutrition Research |date=2019 |publisher=Elsevier |isbn=978-0-12-814556-2 |pages=299–319 |language=en |doi=10.1016/b978-0-12-814556-2.00011-7}}</ref><ref>{{cite journal | vauthors = Clark WF, Sontrop JM, Huang SH, Moist L, Bouby N, Bankir L | title = Hydration and Chronic Kidney Disease Progression: A Critical Review of the Evidence | journal = American Journal of Nephrology | volume = 43 | issue = 4 | pages = 281–292 | date = 2016 | pmid = 27161565 | doi = 10.1159/000445959 | doi-access = free }}</ref>

== Signs and symptoms ==
[[File:PHIL 1939 lores.jpg|thumb|A person with severe dehydration due to [[cholera]], causing sunken eyes and wrinkled hands and skin]]
The hallmarks of dehydration include [[thirst]] and neurological changes such as [[headache]]s, [[Malaise|general discomfort]], loss of [[appetite]], [[nausea]], decreased [[urine]] volume (unless [[polyuria]] is the cause of dehydration), [[mental confusion|confusion]], unexplained [[Fatigue (medical)|tiredness]], purple fingernails, and [[Epileptic seizure|seizures]].<ref>The Handbook Of The SAS And Elite Forces. How The Professionals Fight And Win. Edited by Jon E. Lewis. p.426-Tactics And Techniques, Survival. Robinson Publishing Ltd 1997. {{ISBN|1-85487-675-9}}</ref> The symptoms of dehydration become increasingly severe with greater total body water loss. A body water loss of 1–2%, considered mild dehydration, is shown to impair cognitive performance.<ref>{{cite journal | vauthors = Riebl SK, Davy BM | title = The Hydration Equation: Update on Water Balance and Cognitive Performance | journal = ACSM's Health & Fitness Journal | volume = 17 | issue = 6 | pages = 21–28 | date = November 2013 | pmid = 25346594 | pmc = 4207053 | doi = 10.1249/FIT.0b013e3182a9570f }}</ref> While in people over age 50, the body's thirst sensation diminishes with age, a study found that there was no difference in fluid intake between young and old people.<ref>{{cite journal |author-link=Harriet Hall | vauthors = Hall H |title=Are You Dehydrated? |journal=Skeptical Inquirer |date=August 17, 2020 | volume=4 |issue=4 |url=https://skepticalinquirer.org/exclusive/are-you-dehydrated/}}</ref> Many older people have symptoms of dehydration, with the most common being fatigue.<ref name="Hooper_2015">{{cite journal |vauthors=Hooper L, Abdelhamid A, Attreed NJ, Campbell WW, Channell AM, Chassagne P, Culp KR, Fletcher SJ, Fortes MB, Fuller N, Gaspar PM, Gilbert DJ, Heathcote AC, Kafri MW, Kajii F, Lindner G, Mack GW, Mentes JC, Merlani P, Needham RA, Olde Rikkert MG, Perren A, Powers J, Ranson SC, Ritz P, Rowat AM, Sjöstrand F, Smith AC, Stookey JJ, Stotts NA, Thomas DR, Vivanti A, Wakefield BJ, Waldréus N, Walsh NP, Ward S, Potter JF, Hunter P |date=April 2015 |title=Clinical symptoms, signs and tests for identification of impending and current water-loss dehydration in older people |journal=The Cochrane Database of Systematic Reviews |volume=2015 |issue=4 |article-number=CD009647 |doi=10.1002/14651858.CD009647.pub2 |pmc=7097739 |pmid=25924806 |hdl-access=free |collaboration=Cochrane Kidney and Transplant Group |hdl=2066/110560}}</ref> Dehydration contributes to [[morbidity]] in the elderly population, especially during conditions that promote [[Transepidermal water loss|insensible]] free water losses, such as hot weather.

==Cause==
Risk factors for dehydration include but are not limited to: exerting oneself in hot and humid weather, habitation at high altitudes, endurance athletics, elderly adults, infants, children and people living with chronic illnesses.<ref>{{Cite journal |last1=Paulis |first1=Simone J. C. |last2=Everink |first2=Irma H. J. |last3=Halfens |first3=Ruud J. G. |last4=Lohrmann |first4=Christa |last5=Schols |first5=Jos M. G. A. |date=2018-08-01 |title=Prevalence and Risk Factors of Dehydration Among Nursing Home Residents: A Systematic Review |url=https://www.sciencedirect.com/science/article/abs/pii/S1525861018302639 |journal=Journal of the American Medical Directors Association |volume=19 |issue=8 |pages=646–657 |doi=10.1016/j.jamda.2018.05.009 |pmid=30056949 |issn=1525-8610|url-access=subscription }}</ref><ref>{{Cite journal |last1=Sawka |first1=Michael N |last2=Montain |first2=Scott J |date=2000-08-01 |title=Fluid and electrolyte supplementation for exercise heat stress1234 |url=https://www.sciencedirect.com/science/article/pii/S0002916523067370 |journal=The American Journal of Clinical Nutrition |series=NIH Workshop on the Role of Dietary Supplements for Physically Active People |volume=72 |issue=2 |pages=564S–572S |doi=10.1093/ajcn/72.2.564S |issn=0002-9165|doi-access=free }}</ref><ref>{{Cite journal |last1=Steiner |first1=Michael J. |last2=DeWalt |first2=Darren A. |last3=Byerley |first3=Julie S. |date=2004-06-09 |title=Is This Child Dehydrated? |url=https://jamanetwork.com/journals/jama/article-abstract/198900 |journal=JAMA |volume=291 |issue=22 |pages=2746–2754 |doi=10.1001/jama.291.22.2746 |pmid=15187057 |issn=0098-7484|url-access=subscription }}</ref><ref>{{Citation |last1=Research |first1=Institute of Medicine (US) Committee on Military Nutrition |title=Fluid Metabolism at High Altitudes |date=1996 |work=Nutritional Needs In Cold And In High-Altitude Environments: Applications for Military Personnel in Field Operations |url=https://www.ncbi.nlm.nih.gov/books/NBK232881/ |access-date=2024-11-15 |publisher=National Academies Press (US) |language=en |last2=Marriott |first2=Bernadette M. |last3=Carlson |first3=Sydne J.}}</ref>

Dehydration can also come as a side effect from many different types of drugs and medications.<ref>{{Cite journal |last1=Puga |first1=Ana M. |last2=Lopez-Oliva |first2=Sara |last3=Trives |first3=Carmen |last4=Partearroyo |first4=Teresa |last5=Varela-Moreiras |first5=Gregorio |date=2019-03-20 |title=Effects of Drugs and Excipients on Hydration Status |journal=Nutrients |language=en |volume=11 |issue=3 |page=669 |doi=10.3390/nu11030669 |doi-access=free |issn=2072-6643 |pmc=6470661 |pmid=30897748}}</ref>

In the elderly, blunted response to thirst or inadequate ability to access free water in the face of excess free water losses (especially [[hyperglycemia]] related) seem to be the main causes of dehydration.<ref>{{cite journal | vauthors = Borra SI, Beredo R, Kleinfeld M | title = Hypernatremia in the aging: causes, manifestations, and outcome | journal = Journal of the National Medical Association | volume = 87 | issue = 3 | pages = 220–224 | date = March 1995 | pmid = 7731073 | pmc = 2607819 }}</ref> Excess free water or hypotonic water can leave the body in two ways – [[Transepidermal water loss|''sensible'']] loss such as [[osmotic diuresis]], [[sweating]], [[vomiting]] and [[diarrhea]], and [[Transepidermal water loss|''insensible'']] water loss, occurring mainly through the [[skin]] and [[respiratory tract]]. In humans, dehydration can be caused by a wide range of diseases and states that impair water [[homeostasis]] in the body. These occur primarily through either impaired thirst/water access or sodium excess.<ref>{{cite journal | vauthors = Lindner G, Funk GC | title = Hypernatremia in critically ill patients | journal = Journal of Critical Care | volume = 28 | issue = 2 | pages = 216.e11–216.e20 | date = April 2013 | pmid = 22762930 | doi = 10.1016/j.jcrc.2012.05.001 }}</ref>

== Mechanism ==
[[File:Fluid composition of the body 1.3.png|alt="Fluid composition of the body 1.3" by Alan Sved and David Walsh is licensed under CC BY-SA 4.0.|thumb|384x384px|Diagram depicting the distribution of total body water into percentages of intracellular and extracellular fluid.<ref>{{Cite web | vauthors = Sved A, Walsh D |title=Fluid composition of the body 1.3 |url=https://openverse.org/image/877ec3c8-9c07-4f4c-9739-cc80434e45dd?q=body+fluid+compartments}}</ref>]]Water content of a human body varies from 70–75% in newborns to 40% and less in obese adults,{{sfn|Schoeller|2005|p=35}} an average value of 60% is suggested.<ref>{{Cite book | vauthors = Kamel KS, Halperin ML |title=Fluid, electrolyte, and acid-base physiology: a problem-based approach|date=2017 |publisher=Elsevier |isbn=978-0-323-35515-5 |edition=Fifth |location=Philadelphia, PA}}</ref> Within the body, water is classified as intracellular fluid or extracellular fluid. Intracellular fluid refers to water that is contained within the cells. This consists of approximately 57% of the total body water weight.{{sfn|Schoeller|2005|p=35}} Fluid inside the cells has high concentrations of potassium, magnesium, phosphate, and proteins.<ref name="Garden_2023">{{Cite book | vauthors = Garden J, Parks R, Wigmore S |title=Principles and Practice of Surgery  |publisher=Elsevier Limited |year=2023 |isbn=978-0-7020-8251-1 |edition=8th |pages=32–55}}</ref> Extracellular fluid consists of all fluid outside of the cells, and it includes blood and interstitial fluid. This makes up approximately 43% of the total body water weight. The most common ions in extracellular fluid include sodium, chloride, and bicarbonate.
The concentration of dissolved molecules and ions in the fluid is described as [[Osmotic concentration|Osmolarity]] and is measured in osmoles per liter (Osm/L).<ref name="Garden_2023" /> When the body experiences a free water deficit, the concentration of solutes is increased. This leads to a higher serum osmolarity. When serum osmolarity is elevated, this is detected by osmoreceptors in the hypothalamus. These receptors trigger the release of [[Vasopressin|antidiuretic hormone]] (ADH).<ref>{{Cite book | vauthors = White BA, Harrison JR, Mehlmann LM |title=Endocrine and reproductive physiology |date=2019 |publisher=Elsevier |isbn=978-0-323-59573-5 |edition=5th |series=Mosby physiology series |location=St. Louis, MI}}</ref> ADH resists dehydration by increasing water absorption in the kidneys and constricting blood vessels. It acts on the [[Vasopressin receptor 2|V2 receptors]] in the cells of the collecting tubule of the [[nephron]] to increase expression of [[aquaporin]]. In more extreme cases of low blood pressure, the hypothalamus releases higher amounts of ADH which also acts on V1 receptors.<ref>{{cite journal | vauthors = Webb AJ, Seisa MO, Nayfeh T, Wieruszewski PM, Nei SD, Smischney NJ | title = Vasopressin in vasoplegic shock: A systematic review | journal = World Journal of Critical Care Medicine | volume = 9 | issue = 5 | pages = 88–98 | date = December 2020 | pmid = 33384951 | pmc = 7754532 | doi = 10.5492/wjccm.v9.i5.88 | doi-access = free }}</ref> These receptors cause contractions in the peripheral vascular smooth muscle. This increases systemic vascular resistance and raises blood pressure.

==Diagnosis==
=== Definition ===
Dehydration occurs when water intake does not replace [[free water clearance|free water]] lost due to normal physiologic processes, including [[breathing]], [[urination]], [[perspiration]], or other causes, including [[diarrhea]], and [[vomiting]]. Dehydration can be life-threatening when severe and lead to [[seizure]]s or respiratory arrest, and also carries the risk of [[osmotic cerebral edema]] if [[Fluid replacement|rehydration]] is overly rapid.<ref>{{EMedicine|article|906999|Dehydration}}</ref>

The term "dehydration" has sometimes been used incorrectly as a proxy for the separate, related condition of [[hypovolemia]], which specifically refers to a decrease in volume of [[blood plasma]].<ref name="Mange K 1997"/> The two are regulated through independent mechanisms in humans;<ref name="Mange K 1997"/> the distinction is important in guiding treatment.<ref name="Bhave G 2011">{{cite journal | vauthors = Bhave G, Neilson EG | title = Volume depletion versus dehydration: how understanding the difference can guide therapy | journal = American Journal of Kidney Diseases | volume = 58 | issue = 2 | pages = 302–309 | date = August 2011 | pmid = 21705120 | pmc = 4096820 | doi = 10.1053/j.ajkd.2011.02.395 }}</ref>

=== Physical examination ===
[[File:UOTW 59 - Ultrasound of the Week 1.webm|thumb|Ultrasound of the blood vessels of the neck that supports the diagnosis of severe dehydration<ref>
{{cite web|title=UOTW#59 - Ultrasound of the Week|url=https://www.ultrasoundoftheweek.com/uotw-59/|website=Ultrasound of the Week|access-date=27 May 2017|date=23 September 2015}}</ref>|229x229px]]Common exam findings of dehydration include dry mucous membranes, dry axillae, increased capillary refill time, sunken eyes, and poor [[skin turgor]].<ref>{{Cite journal | vauthors = Huffman GB |date=1999-09-15 |title=Establishing a Bedside Diagnosis of Hypovolemia |url=https://www.aafp.org/pubs/afp/issues/1999/0915/p1220a.html |journal=American Family Physician |language=en-US |volume=60 |issue=4 |pages=1220–1225}}</ref><ref name = "Hooper_2015" /> More extreme cases of dehydration can lead to orthostatic hypotension, dizziness, weakness, and altered mental status.<ref>{{Cite journal | vauthors = Braun MM, Barstow CH, Pyzocha NJ |date=2015-03-01 |title=Diagnosis and Management of Sodium Disorders: Hyponatremia and Hypernatremia |url= https://www.aafp.org/pubs/afp/issues/2015/0301/p299.html#:~:text=33-,DIAGNOSTIC%20APPROACH,sodium%20gain%20(Table%202).&text=Patients%20are%20often%20asymptomatic%20but,12%20(Figure%20335%20). |journal=American Family Physician |language=en-US |volume=91 |issue=5 |pages=299–307|pmid=25822386 }}</ref> Depending on the underlying cause of dehydration, other symptoms may be present as well. Excessive sweating from exercise may be associated with muscle cramps. Patients with gastrointestinal water loss from vomiting or diarrhea may also have fever or other systemic signs of infection.

The skin turgor test can be used to support the diagnosis of dehydration. The skin turgor test is conducted by pinching skin on the patient's body, in a location such as the forearm or the back of the hand, and watching to see how quickly it returns to its normal position. The skin turgor test can be unreliable in patients who have reduced skin elasticity, such as the elderly.<ref>{{Cite book | vauthors = Thomas J, Monaghan T |url= https://books.google.com/books?id=PF-yAwAAQBAJ |title=Oxford Handbook of Clinical Examination and Practical Skills |date=2014 |publisher=Oxford University Press |isbn=978-0-19-959397-2 |language=en}}</ref>

=== Laboratory tests ===
While there is no single gold standard test to diagnose dehydration, evidence can be seen in multiple laboratory tests involving blood and urine. Serum osmolarity above 295 mOsm/kg is typically seen in dehydration due to free water loss.<ref name = "Hooper_2015" /> A urinalysis, which is a test that performs chemical and microscopic analysis of urine, may find darker color or foul odor with severe dehydration.<ref>{{Cite book | vauthors = Hughes G |title=A medication guide to internal medicine tests and procedures |date=2021 |publisher=Elsevier, Inc |isbn=978-0-323-79007-9 |edition=First |location=Philadelphia}}</ref> Urinary sodium also provides information about the type of dehydration. For hyponatremic dehydration, such as from vomiting or diarrhea, urinary sodium will be less than 10&nbsp;mmol/L due to increased sodium retention by the kidneys in an effort to conserve water.<ref>{{Citation |last=Tietze |first=Karen J. |title=Review of Laboratory and Diagnostic Tests |date=2012 |work=Clinical Skills for Pharmacists |pages=86–122 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780323077385100055 |access-date=2024-11-06 |publisher=Elsevier |language=en |doi=10.1016/b978-0-323-07738-5.10005-5 |isbn=978-0-323-07738-5|url-access=subscription }}</ref> In dehydrated patients with sodium loss due to diuretics or renal dysfunction, urinary sodium may be elevated above 20&nbsp;mmol/L.<ref>{{Cite journal |last1=Yun |first1=Giae |last2=Baek |first2=Seon Ha |last3=Kim |first3=Sejoong |date=2023-05-01 |title=Evaluation and management of hypernatremia in adults: clinical perspectives |journal=The Korean Journal of Internal Medicine |language=en |volume=38 |issue=3 |pages=290–302 |doi=10.3904/kjim.2022.346 |issn=1226-3303 |pmc=10175862 |pmid=36578134}}</ref> Patients may also have elevated serum levels of [[blood urea nitrogen]] (BUN) and [[creatinine]]. Both of these molecules are normally excreted by the kidney, but when the circulating blood volume is low, the kidney can become injured.<ref>{{Cite journal |last1=Mohamed |first1=Mohamed Saied |last2=Martin |first2=Andrew |date=May 2024 |title=Acute kidney injury in critical care |url=https://linkinghub.elsevier.com/retrieve/pii/S1472029924000456 |journal=Anaesthesia & Intensive Care Medicine |language=en |volume=25 |issue=5 |pages=308–315 |doi=10.1016/j.mpaic.2024.03.008|url-access=subscription }}</ref> This causes decreased kidney function and results in elevated BUN and creatinine in the serum.<ref>{{Citation |last1=Amin |first1=Rasheda |title=Kidney and urinary tract disorders |date=2021 |work=Biochemical and Molecular Basis of Pediatric Disease |pages=167–228 |url=https://linkinghub.elsevier.com/retrieve/pii/B978012817962800010X |access-date=2024-11-06 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-817962-8.00010-x |isbn=978-0-12-817962-8 |last2=Ahn |first2=Sun-Young |last3=Moudgil |first3=Asha|url-access=subscription }}</ref> {{Further|Portsmouth sign}}

== Prevention ==
For routine activities, thirst is normally an adequate guide to maintain proper hydration.<ref>{{Cite book | url= http://www.nationalacademies.org/hmd/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx |title=Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate: Health and Medicine Division |isbn=978-0-309-09169-5|language=en|access-date=2018-02-07 | author1 = Institute of Medicine | author2 = Food Nutrition Board |date=June 18, 2005|publisher=National Academies Press }}</ref> Minimum water intake will vary individually depending on weight, energy expenditure, age, sex, physical activity, environment, diet, and genetics.<ref>{{Cite journal |last1=Armstrong |first1=Lawrence E. |last2=Johnson |first2=Evan C. |date=2018-12-05 |title=Water Intake, Water Balance, and the Elusive Daily Water Requirement |journal=Nutrients |language=en |volume=10 |issue=12 |page=1928 |doi=10.3390/nu10121928 |doi-access=free |issn=2072-6643 |pmc=6315424 |pmid=30563134}}</ref><ref>{{cite journal | vauthors = Yamada Y, Zhang X, Henderson ME, Sagayama H, Pontzer H, Watanabe D, Yoshida T, Kimura M, Ainslie PN, Andersen LF, Anderson LJ, Arab L, Baddou I, Bedu-Addo K, Blaak EE, Blanc S, Bonomi AG, Bouten CV, Bovet P, Buchowski MS, Butte NF, Camps SG, Close GL, Cooper JA, Cooper R, Das SK, Dugas LR, Eaton S, Ekelund U, Entringer S, Forrester T, Fudge BW, Goris AH, Gurven M, Halsey LG, Hambly C, El Hamdouchi A, Hoos MB, Hu S, Joonas N, Joosen AM, Katzmarzyk P, Kempen KP, Kraus WE, Kriengsinyos W, Kushner RF, Lambert EV, Leonard WR, Lessan N, Martin CK, Medin AC, Meijer EP, Morehen JC, Morton JP, Neuhouser ML, Nicklas TA, Ojiambo RM, Pietiläinen KH, Pitsiladis YP, Plange-Rhule J, Plasqui G, Prentice RL, Rabinovich RA, Racette SB, Raichlen DA, Ravussin E, Redman LM, Reilly JJ, Reynolds RM, Roberts SB, Schuit AJ, Sardinha LB, Silva AM, Sjödin AM, Stice E, Urlacher SS, Valenti G, Van Etten LM, Van Mil EA, Wells JC, Wilson G, Wood BM, Yanovski JA, Murphy-Alford AJ, Loechl CU, Luke AH, Rood J, Westerterp KR, Wong WW, Miyachi M, Schoeller DA, Speakman JR | title = Variation in human water turnover associated with environmental and lifestyle factors | journal = Science | volume = 378 | issue = 6622 | pages = 909–915 | date = November 2022 | pmid = 36423296 | pmc = 9764345 | doi = 10.1126/science.abm8668 | bibcode = 2022Sci...378..909I }}</ref> With exercise, exposure to hot environments, or a [[Adipsia|decreased thirst response]], additional water may be required. In [[athlete]]s in competition, drinking to [[thirst]] optimizes performance and safety, despite weight loss, and as of 2010, there was no scientific study showing that it is beneficial to stay ahead of thirst and maintain weight during exercise.<ref>{{cite journal | vauthors = Noakes TD | title = Is drinking to thirst optimum? | journal = Annals of Nutrition & Metabolism | volume = 57 | issue = Suppl 2 | pages = 9–17 | date = 2010 | pmid = 21346332 | doi = 10.1159/000322697 | doi-access = free }}</ref>

In warm or humid weather, or during heavy exertion, water loss can increase markedly, because humans have a large and widely variable capacity for sweating. Whole-body sweat losses in men can exceed 2 L/h during [[competitive sport]], with rates of 3–4 L/h observed during short-duration, high-intensity exercise in the heat.<ref name="ReferenceA">{{cite journal | vauthors = Taylor NA, Machado-Moreira CA | title = Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans | journal = Extreme Physiology & Medicine | volume = 2 | issue = 1 | page = 4 | date = February 2013 | pmid = 23849497 | pmc = 3710196 | doi = 10.1186/2046-7648-2-4 | doi-access = free }}</ref> When such large amounts of water are being lost through perspiration, [[electrolytes]], especially sodium, are also being lost.<ref>{{Cite journal |last=Baker |first=Lindsay B. |date=March 2017 |title=Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability |journal=Sports Medicine |language=en |volume=47 |issue=S1 |pages=111–128 |doi=10.1007/s40279-017-0691-5 |issn=0112-1642 |pmc=5371639 |pmid=28332116}}</ref>

In most athletes exercising and sweating for 4–5 hours with a sweat sodium concentration of less than 50&nbsp;mmol/L, the total sodium lost is less than 10% of total body stores (total stores are approximately 2,500&nbsp;mmol, or 58 g for a 70-kg person).<ref name="Edward F Coyle 2004">{{cite journal | vauthors = Coyle EF | title = Fluid and fuel intake during exercise | journal = Journal of Sports Sciences | volume = 22 | issue = 1 | pages = 39–55 | date = January 2004 | pmid = 14971432 | doi = 10.1080/0264041031000140545 | s2cid = 14693195 | citeseerx = 10.1.1.321.6991 }}</ref> These losses appear to be well tolerated by most people. The inclusion of sodium in fluid replacement drinks has some theoretical benefits<ref name="Edward F Coyle 2004"/> and poses little or no risk, so long as these fluids are hypotonic (since the mainstay of dehydration prevention is the replacement of free water losses).

== Treatment ==
{{Main|Management of dehydration}}{{Redirect|Rehydrated|the SpongeBob video game remaster|SpongeBob SquarePants: Battle for Bikini Bottom – Rehydrated}}
The most effective treatment for minor dehydration is widely considered to be drinking water and reducing fluid loss. Plain water restores only the volume of the blood plasma, inhibiting the thirst mechanism before solute levels can be replenished.<ref>{{cite book | vauthors = Murray R, Stofan J  |chapter=Ch. 8: Formulating carbohydrate-electrolyte drinks for optimal efficacy | veditors = Maughan RJ, Murray R |title=Sports Drinks: Basic Science and Practical Aspects |chapter-url=https://books.google.com/books?id=bS12dnUsGJcC&pg=PA197 |year=2001 |publisher=CRC Press |isbn=978-0-8493-7008-3 |pages=197–224}}</ref> Consumption of solid foods can also contribute to hydration. It is estimated approximately 22% of American water intake comes from food.<ref>{{Cite journal |last1=Popkin |first1=Barry M |last2=D'Anci |first2=Kristen E |last3=Rosenberg |first3=Irwin H |date=August 2010 |title=Water, hydration, and health: Nutrition Reviews©, Vol. 68, No. 8 |journal=Nutrition Reviews |language=en |volume=68 |issue=8 |pages=439–458 |doi=10.1111/j.1753-4887.2010.00304.x |pmc=2908954 |pmid=20646222}}</ref> Urine concentration and frequency will return to normal as dehydration resolves.<ref>{{Cite journal |last1=Ostermann |first1=Marlies |last2=Shaw |first2=Andrew D. |last3=Joannidis |first3=Michael |date=2023-01-01 |title=Management of oliguria |url=https://link.springer.com/article/10.1007/s00134-022-06909-5 |journal=Intensive Care Medicine |language=en |volume=49 |issue=1 |pages=103–106 |doi=10.1007/s00134-022-06909-5 |pmid=36266588 |issn=1432-1238}}</ref>

In some cases, correction of a dehydrated state is accomplished by the replenishment of necessary water and [[electrolyte]]s (through [[oral rehydration therapy]], or [[fluid replacement]] by [[intravenous therapy]]). As oral rehydration is less painful, non-invasive, inexpensive, and easier to provide, it is the treatment of choice for mild dehydration.<ref>{{Cite journal |last1=Aghsaeifard |first1=Ziba |last2=Heidari |first2=Ghobad |last3=Alizadeh |first3=Reza |date=September 2022 |title=Understanding the use of oral rehydration therapy: A narrative review from clinical practice to main recommendations |journal=Health Science Reports |language=en |volume=5 |issue=5 |article-number=e827 |doi=10.1002/hsr2.827 |issn=2398-8835 |pmc=9464461 |pmid=36110343}}</ref> Solutions used for intravenous rehydration may be [[Isotonicity|isotonic]], [[Tonicity#Hypertonic solution|hypertonic]], or hypotonic depending on the cause of dehydration as well as the sodium concentration in the blood.<ref>{{Cite journal |last=Kim |first=Soo Wan |date=2006 |title=Hypernatemia: Successful Treatment |journal=Electrolytes & Blood Pressure |language=en |volume=4 |issue=2 |pages=66–71 |doi=10.5049/EBP.2006.4.2.66 |issn=1738-5997 |pmc=3894528 |pmid=24459489}}</ref> Pure water injected into the veins will cause the breakdown ([[lysis]]) of red blood cells ([[erythrocytes]]).<ref>{{Cite journal |last=Tinawi |first=Mohammad |date=2021-04-21 |title=New Trends in the Utilization of Intravenous Fluids |journal=Cureus |volume=13 |issue=4 |article-number=e14619 |language=en |doi=10.7759/cureus.14619 |doi-access=free |issn=2168-8184 |pmc=8140055 |pmid=34040918}}</ref>

When [[fresh water]] is unavailable (e.g. at sea or in a desert), [[seawater]] or drinks with significant [[Ethanol|alcohol]] concentration will worsen dehydration. [[Urine]] contains a lower solute concentration than seawater; this requires the kidneys to create more urine to remove the excess salt, causing more water to be lost than was consumed from seawater.<ref>{{Cite book |last1=Hall |first1=John E. |title=Guyton and Hall textbook of medical physiology |last2=Hall |first2=Michael E. |last3=Guyton |first3=Arthur C. |date=2021 |publisher=Elsevier |isbn=978-0-323-67280-1 |edition=14th |location=Philadelphia, PA}}</ref>

For severe cases of dehydration where [[fainting]], [[unconsciousness]], or other severely inhibiting symptoms are present (the patient is incapable of standing upright or thinking clearly), emergency attention is required. Fluids containing a proper balance of replacement electrolytes are given orally or intravenously with continuing assessment of electrolyte status; complete resolution is normal in all but the most extreme cases.<ref>{{Cite journal |last1=Gawronska |first1=Julia |last2=Koyanagi |first2=Ai |last3=López Sánchez |first3=Guillermo F. |last4=Veronese |first4=Nicola |last5=Ilie |first5=Petre Cristian |last6=Carrie |first6=Anne |last7=Smith |first7=Lee |last8=Soysal |first8=Pinar |date=2022-12-31 |title=The Prevalence and Indications of Intravenous Rehydration Therapy in Hospital Settings: A Systematic Review |journal=Epidemiologia |language=en |volume=4 |issue=1 |pages=18–32 |doi=10.3390/epidemiologia4010002 |doi-access=free |issn=2673-3986 |pmc=9844368 |pmid=36648776}}</ref><ref>{{cite journal | vauthors = Ellershaw JE, Sutcliffe JM, Saunders CM | title = Dehydration and the dying patient | journal = Journal of Pain and Symptom Management | volume = 10 | issue = 3 | pages = 192–197 | date = April 1995 | pmid = 7629413 | doi = 10.1016/0885-3924(94)00123-3 | doi-access = free }}</ref>

== Prognosis ==
The prognosis for dehydration depends on the cause and extent of dehydration. Mild dehydration normally resolves with oral hydration. Chronic dehydration, such as from physically demanding jobs or decreased thirst, can lead to [[chronic kidney disease]].<ref>{{Cite journal |last1=El Khayat |first1=Moussa |last2=Halwani |first2=Dana A. |last3=Hneiny |first3=Layal |last4=Alameddine |first4=Ibrahim |last5=Haidar |first5=Mustapha A. |last6=Habib |first6=Rima R. |date=2022-02-08 |title=Impacts of Climate Change and Heat Stress on Farmworkers' Health: A Scoping Review |journal=Frontiers in Public Health |volume=10 |doi=10.3389/fpubh.2022.782811 |doi-access=free |issn=2296-2565 |pmc=8861180 |pmid=35211437}}</ref> Elderly people with dehydration are at higher risk of confusion, [[urinary tract infection]]s, falls, and even delayed wound healing.<ref>{{Cite journal |last1=Bruno |first1=Chevonne |last2=Collier |first2=Annaleise |last3=Holyday |first3=Margaret |last4=Lambert |first4=Kelly |date=2021-10-18 |title=Interventions to Improve Hydration in Older Adults: A Systematic Review and Meta-Analysis |journal=Nutrients |language=en |volume=13 |issue=10 |page=3640 |doi=10.3390/nu13103640 |doi-access=free |issn=2072-6643 |pmc=8537864 |pmid=34684642}}</ref> In children with mild to moderate dehydration, oral hydration is adequate for a full recovery.<ref>{{Cite journal |last1=Canavan |first1=Amy |last2=Billy S. Arant |first2=Jr |date=2009-10-01 |title=Diagnosis and Management of Dehydration in Children |url=https://www.aafp.org/pubs/afp/issues/2009/1001/p692.html |journal=American Family Physician |language=en-US |volume=80 |issue=7 |pages=692–696|pmid=19817339 }}</ref>

== See also ==
* [[Hydrational fluid]]s
* [[Terminal dehydration]]
* [[Dryness (medical)]]
* [[Hypernatremia]]

== References ==
{{Reflist}}

== Further reading ==
{{Refbegin}}
* {{cite journal | vauthors = Byock I | title = Patient refusal of nutrition and hydration: walking the ever-finer line | journal = The American Journal of Hospice & Palliative Care | volume = 12 | issue = 2 | pages = 8, 9-8,13 | year = 1995 | pmid = 7605733 | doi = 10.1177/104990919501200205 | s2cid = 46385519 | author-link = Ira Byock }}
* {{cite book|first=Dale A.|last=Schoeller|editor-last=Heymsfield|editor-first=S.|title=Human Body Composition|publisher=Human Kinetics|chapter=Hydrometry|issue=v. 918|year=2005|isbn=978-0-7360-4655-8|chapter-url=https://books.google.com/books?id=_WoPgY4KAxgC&pg=PA35|access-date=2025-01-24}}
* {{cite journal | vauthors = Steiner MJ, DeWalt DA, Byerley JS | title = Is this child dehydrated? | journal = JAMA | volume = 291 | issue = 22 | pages = 2746–2754 | date = June 2004 | pmid = 15187057 | doi = 10.1001/jama.291.22.2746 | author-link3 = Julie Story Byerley }}
{{Refend}}

== External links ==
{{wiktionary}}
* [https://www.medlineplus.gov/ency/article/000982.htm#visualContent Definition of dehydration by the U.S. National Institutes of Health's MedlinePlus medical encyclopedia]

{{Medical resources
| DiseasesDB      = 3520
| ICD10           = {{ICD10|E|86||e|70}}
| ICD9            = {{ICD9|276.51}}
| ICDO            =
| OMIM            =
| MedlinePlus     = 000982
| eMedicineSubj   = article
| eMedicineTopic  = 801012
| MeSH            = D003681
| GeneReviewsNBK  =
| GeneReviewsName =
| ICD10CM         = {{ICD10CM|E86.0}}
}}
{{Fluid, electrolyte, acid base metabolic pathology}}
{{Nutritional pathology}}
{{Authority control}}

[[Category:Dehydration| ]]
[[Category:Causes of death]]
[[Category:Nutrition]]
[[Category:Symptoms and signs]]
[[Category:Wilderness medical emergencies]]