Water intoxication
SpecialtyToxicology, critical care medicine

Water intoxication, also known as water poisoning, hyperhydration, overhydration, or water toxemia, is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside safe limits by excessive water intake.

Under normal circumstances, accidentally consuming too much water is exceptionally rare. Nearly all deaths related to water intoxication in normal individuals have resulted either from water-drinking contests, in which individuals attempt to consume large amounts of water, or from long bouts of exercise during which excessive amounts of fluid were consumed.[1] In addition, water cure, a method of torture in which the victim is forced to consume excessive amounts of water, can cause water intoxication.[1]

Water, just like any other substance, can be considered a poison when over-consumed in a brief period of time. Water intoxication mostly occurs when water is being consumed in a high quantity without adequate electrolyte intake.[2]

Excess of body water may also be a result of a medical condition or improper treatment; see "hyponatremia" for some examples. Water is considered one of the least toxic chemical compounds, with an LD50 exceeding 90 ml/kg in rats;[3] drinking 6 liters in three hours has caused the death of a human.[4]

Risk factors

Low body mass (infants)

It can be very easy for children under one year old (especially those under nine months) to absorb too much water. Because of their small body mass, it is easy for them to take in a large amount of water relative to body mass and total body sodium stores.[5]

Endurance sports

Marathon runners are susceptible to water intoxication if they drink too much while running. This is caused when sodium levels drop below 135 mmol/L when athletes consume large amounts of fluid. This has been noted to be the result of the encouragement of excessive fluid replacement by various guidelines. This has largely been identified in marathon runners as a dilutional hyponatremia.[6] A study conducted on runners completing the 2002 Boston Marathon found that thirteen percent finished the race with hyponatremia. The study concluded that the strongest predictor of hyponatremia was weight gain while racing (over-hydration), and hyponatremia was just as likely to occur in runners who chose sports drinks as those who chose water.[6]

Military training

Hyponatremia and other physical conditions associated with water intoxication are more often seen in those participating in military training. One US Army study found 17 trainees were admitted to hospital over a year's period for water intoxication[7] while another found that three soldiers had died, leading to a recommendation that no more than 1–1.5 L of water should be consumed per hour of heavy sweating.[8]

Overexertion and heat stress

Any activity or situation that promotes heavy sweating can lead to water intoxication when water is consumed to replace lost fluids. Persons working in extreme heat and/or humidity for long periods must take care to drink and eat in ways that help to maintain electrolyte balance. People using drugs such as MDMA (often referred to colloquially as "Ecstasy") may overexert themselves, perspire heavily, feel increased thirst, and then drink large amounts of water to rehydrate, leading to electrolyte imbalance and water intoxication – this is compounded by MDMA use increasing the levels of antidiuretic hormone (ADH), decreasing the amount of water lost through urination.[9] Even people who are resting quietly in extreme heat or humidity may run the risk of water intoxication if they drink large amounts of water over short periods for rehydration.

Psychiatric conditions

Psychogenic polydipsia is the psychiatric condition in which patients feel compelled to drink large quantities of water, thus putting them at risk of water intoxication. This condition can be especially dangerous if the patient also exhibits other psychiatric indications (as is often the case), as the care-takers might misinterpret the hyponatremic symptoms.[10]


When an unconscious person is being fed intravenously (for example, total parenteral nutrition) or via a nasogastric tube, the fluids given must be carefully balanced in composition to match fluids and electrolytes lost. These fluids are typically hypertonic, and so water is often co-administered. If the electrolytes are not monitored (even in an ambulatory patient), either hypernatremia or hyponatremia may result.[11]

Some neurological/psychiatric medications (oxcarbazepine, among others) have been found to cause hyponatremia in some patients.[12] Patients with diabetes insipidus are particularly vulnerable due to rapid fluid processing.[13]


At the onset of this condition, fluid outside the cells has an excessively low amount of solutes, such as sodium and other electrolytes, in comparison to fluid inside the cells, causing the fluid to move into the cells to balance its osmotic concentration. This causes the cells to swell. The swelling increases intracranial pressure in the brain, which leads to the first observable symptoms of water intoxication: headache, personality changes, changes in behavior, confusion, irritability, and drowsiness. These are sometimes followed by difficulty breathing during exertion, muscle weakness and pain, twitching, or cramping, nausea, vomiting, thirst, and a dulled ability to perceive and interpret sensory information. As the condition persists, papillary and vital signs may result including bradycardia and widened pulse pressure. The cells in the brain may swell to the point where blood flow is interrupted resulting in cerebral edema. Swollen brain cells may also apply pressure to the brain stem causing central nervous system dysfunction. Both cerebral edema and interference with the central nervous system are dangerous and could result in seizures, brain damage, coma or death.[14]


Water intoxication can be prevented if a person's intake of water does not grossly exceed their losses. Healthy kidneys are able to excrete approximately 800 millilitres to one litre of fluid water (0.84–1.04 quarts) per hour.[15] However, stress (from prolonged physical exertion), as well as disease states, can greatly reduce this amount.[15]


Mild intoxication may remain asymptomatic and require only fluid restriction. In more severe cases, treatment consists of:

Notable cases

See also


  1. ^ a b Noakes TD, Speedy DB (July 2006). "Case proven: exercise associated hyponatraemia is due to overdrinking. So why did it take 20 years before the original evidence was accepted?". British Journal of Sports Medicine. 40 (7): 567–72. doi:10.1136/bjsm.2005.020354. PMC 2564296. PMID 16799109.
  2. ^ Farrell DJ, Bower L (Oct 2003). "Fatal water intoxication". Journal of Clinical Pathology. 56 (10): 803–804. doi:10.1136/jcp.56.10.803-a. PMC 1770067. PMID 14514793.
  3. ^ "Section 11: Toxicological Information". Material Safety Data Sheet Water MSDS (Report). ScienceLab.com. Archived from the original on 29 September 2019.
  4. ^ Ballantyne, Coco (21 June 2007). "Strange but True: Drinking Too Much Water Can Kill". Scientific American.
  5. ^ "Water Intoxication in Infants". Retrieved 31 August 2015.
  6. ^ a b Almond CS, Shin AY, Fortescue EB, et al. (April 2005). "Hyponatremia among runners in the Boston Marathon". The New England Journal of Medicine. 352 (15): 1550–6. doi:10.1056/NEJMoa043901. PMID 15829535.
  7. ^ O'Brien, K. K.; Montain, S. J.; Corr, W. P.; Sawka, M. N.; Knapik, J. J.; Craig, S. C. (May 2001). "Hyponatremia associated with overhydration in U.S. Army trainees". Military Medicine. pp. 405–410.
  8. ^ Gardner, John W. (May 2002). "Death by water intoxication". Military Medicine. pp. 432–434.
  9. ^ Timbrell, John (2005). The Poison Paradox: Chemicals as Friends and Foes. OUP Oxford. ISBN 978-0-19-280495-2.
  10. ^ Zerbe, Robert L.; Robertson, Gary L. (1981-12-24). "A Comparison of Plasma Vasopressin Measurements with a Standard Indirect Test in the Differential Diagnosis of Polyuria". New England Journal of Medicine. 305 (26): 1539–1546. doi:10.1056/NEJM198112243052601. ISSN 0028-4793. PMID 7311993.
  11. ^ Schwaderer AL, Schwartz GJ (April 2005). "Treating hypernatremic dehydration". Pediatrics in Review. 26 (4): 148–50. doi:10.1542/pir.26-4-148. PMID 15805238.
  12. ^ "Oxcarbazepine". Archived from the original on 23 October 2016. Retrieved 31 August 2015.
  13. ^ "What Is Diabetes Insipidus?". Archived from the original on 2010-07-29. Retrieved 2011-12-02.
  14. ^ Moreau, David (2008). Fluids & Electrolytes Made Incredibly Easy! (4th ed.). Philadelphia: Lippincott Williams & Wilkins. pp. 75–77. ISBN 978-1582555652.
  15. ^ a b Coco Ballantyne. "Strange but True: Drinking Too Much Water Can Kill". Retrieved 31 August 2015.
  16. ^ Asbridge, Thomas (2010). The Crusades: The Authoritative History of the War for the Holy Land. HarperCollins. p. 90.
  17. ^ "Care Faulted In the Death Of Warhol". NYT. Retrieved 27 October 2013.
  18. ^ "Hyponatremia ("Water Intoxication")". The DEA.org. Retrieved May 10, 2007.
  19. ^ Grice, Elizabeth (August 21, 2003). "My battle with the bottle". The Daily Telegraph. London.
  20. ^ Valentine Low (3 July 2003). "Actor tells of water overdose". Evening Standard. Retrieved 31 August 2015.
  21. ^ "Woman dies after being in water-drinking contest". LA Times. 2007-01-14. Archived from the original on 2020-04-19. Retrieved 2020-04-19.
  22. ^ "Ten Fired After Radio Contest Tragedy". www.cbsnews.com. Retrieved 2019-02-02.
  23. ^ "$16M Awarded In Water Drinking Death". ABC News. 2009-11-02. Retrieved 2019-02-02.
  24. ^ "Couple accused of killing son by forcing him to drink water". CTVNews. June 17, 2020.