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Water intoxication

What is water intoxication?

Water intoxication means a drop of blood sodium bellow 130 mmol/liter (hyponatremia) as a result of excessive water intake [1]. Water intoxication can occur when you consume too much water and too little salt in a short time.

The maximal safe amount of water per day for most healthy adults on a regular diet (with some sodium consumption) is probably up to 15 liters. For those who do not consume any sodium (for example, during fasting), it is probably safe to consume up to 5 liters of water per day.

The maximal safe amount of water per hour (when drunk for several hours in a row) for most healthy adults is about 1.4 liters, according to “Current U.S. Military Fluid Replacement Guidelines” from 2003 [2]. However, theoretically, consuming as little as 700 mL of water per hour for several hours in the row, especially when consuming very little sodium, may result in hyponatremia due to water retention, since the maximal water excretion capacity of the kidneys in some people may be only 600 mL of urine per hour [4]. According to various sources, in different healthy adults the kidneys can excrete 600-1,500 mL of the urine per hour [4,12].

People have died after drinking, for example, 3-4 liters of water in few hours (a woman, 40 years; 2 girls, 3 and 4 years) [5,6,7], 6 liters in few hours (a girl, 12 years) [8] or 3 gallons, that is 11 liters, probably within few hours (a 25 years old man after a bike ride) [9].

Causes and Risk Factors

  • “Water fasting,” “water only diet” or “detox diet” as a weight loss method
  • Water drinking contests
  • Drinking large amounts of beer without eating (beer potomania)
  • Psychological disorders with excessive thirst (psychogenic polydipsia)
  • Marathon or triathlon running, cycling or hard physical work, lasting for more than 5 hours, in a hot climate in combination with excessive drinking and insufficient sodium intake; slow, small women marathon runners who drink more than they sweat seem to be at greatest risk [11].
  • Aspirin, ibuprofen or other nonsteroidal anti-inflammatory drugs (NSAIDs) may stimulate sodium loss through the kidneys and thus increase the risk of hyponatremia in athletes [10].
  • Disorders with low blood sodium levels (hyponatremia): advanced kidney failure, adrenal insufficiency, congestive heart failure, syndrome of inappropriate ADH secretion (SIADH), thiazide diuretics
  • In infants: feeding an infant with formula diluted with water. Several cases of seizures [13,14] and even death from water intoxication in infants after consuming diluted formula were reported.


Symptoms may include headache, weakness, nausea or vomiting, swollen hands and feet and, in severe cases, muscle cramps, wheezy breathing (due to pulmonary edema), confusion, seizures, coma or death (due to brain swelling ─ cerebral edema) [1].

The main sign of water intoxication is a sudden weight gain, and sometimes, swelling of the feet. Water intoxication can occur without weight gain and even with moderate weight loss due to dehydration [1].

Diagnosis. In water intoxication, blood sodium levels are decreased [3].

Treatment of water intoxication may include infusion of hypertonic saline, diuretics, steroids and other drugs [3].

Prevention. It is not likely you will suffer from water intoxication by drinking too much by accident in an everyday scenario. During marathon, you can avoid water intoxication by drinking only to thirst and regular sodium consumption from usual foods before the race. Note, that relatively low amount of sodium in commercial sport drinks, when drunk in excess, does not prevent water intoxication.

  1. Scott JM, 2008, Strategies to Prevent Hyponatremia During Prolonged Exercise  Current Sports Medicine Reports
  2. Kolka MA et al, 2003, Current U.S. Military Fluid Replacement Guidelines  ResearchGate
  3. Craig S, Hyponatremia in Emergency Medicine Treatment & Management  Emedicine
  4. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate ( 2005 )/4 Water  The National Academic Press
  5. 008, Dec 12th, Woman died from ‘too much water’  BBC News
  6. 2007, March 7th, Woman competent for trial  Sun Sentinel
  7. 2005, October 13th, Split verdict surprises and stuns the Killpacks  Deseret News
  8. 2012, July 6th, Girl drinks herself to death in ‘water poker’  The Local
  9. 2005, August 11th, District Officer Dies After Bike Ride  The Washington Post
  10. Salt and the ultraendurance athlete  Rice University
  11. 2007, Exercise and Fluid Replacement  Medicine & Science in Sports & Medicine
  12. Rosner MH, 2007, Exercise-Associated Hyponatremia  Clinical Journal of the American Society of Nephrology
  13. Hyponatremic Seizures Among Infants Fed with Commercial Bottled Drinking Water — Wisconsin, 1993  Centers of Disease Control and Prevention
  14. Wong KC, 2002, Water Intoxication in a 7-month Infant  Hong Kong Journal of Pediatrics

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