Water Intoxication: What Happens When You Drink Too Much Water?

Maybe your like

Medical News TodaySubscribeWhat happens if you drink too much water?

Medically reviewed by Adrienne Seitz, MS, RD, LDN, Nutrition — Written by Arlene Semeco, MS, RD — Updated on April 10, 2025

Water intoxication
Dangers
Causes
FAQ
Summary

The body needs water to function correctly, but drinking too much too fast can have serious health consequences. The kidneys can only remove 0.8 to 1.0 liters (L) of water per hour, and a very high water intake can upset the body’s electrolyte balance.

It is difficult to drink too much water by accident, but it can happen, usually as a result of overhydrating during sporting events or intense training.

The symptoms of water intoxication can be vague or unspecific. They can include confusion, disorientation, nausea, and vomiting.

In rare cases, water intoxication can cause swelling in the brain and become fatal.

This article describes the symptoms, causes, and effects of water intoxication. It also looks into how much water a person should drink each day.

What is water intoxication?

Also known as water poisoning, water intoxication is a disruption of brain function caused by drinking too much water.

Doing so increases the amount of water in the blood. This can dilute the electrolytes, especially sodium, in the blood.

If sodium levels fall below 135 millimoles per liter (mmol/l), doctors refer to the issue as hyponatremia.

Sodium helps maintain the balance of fluids inside and outside of cells. When sodium levels drop due to excessive water consumption, fluids travel from the outside to the inside of cells, causing them to swell.

When this happens to brain cells, it can be dangerous and even life threatening.

Dangers of drinking too much water

When a person consumes an excessive amount of water and cells in their brain start to swell, the pressure inside their skull increases. This causes the first symptoms of water intoxication, which include:

headaches
nausea
vomiting

Severe cases of water intoxication can produce more serious symptoms, such as:

drowsiness
muscle weakness or cramping
increased blood pressure
double vision
confusion
inability to identify sensory information
difficulty breathing

A buildup of fluid in the brain is called cerebral edema. This can affect the brain stem and cause central nervous system dysfunction.

In severe cases, water intoxication can cause seizures, brain damage, a coma, and even death.

What can cause water intoxication?

Water intoxication is rare, and it is very difficult to consume too much water by accident. However, it can happen.

Water intoxication most commonly affects people participating in sporting events or endurance training or people who have various mental health conditions.

Sporting events

Water intoxication can occur in endurance athletes if they drink a lot of water without correctly accounting for electrolyte losses.

For this reason, hyponatremia often occurs during major sporting events.

As the authors of one older study report, out of 488 participants in the 2002 Boston Marathon, 13% had hyponatremia symptoms, and 0.6% had critical hyponatremia, with sodium levels of less than 120 mmol/l.

The risk of hyponatremia is higher in sporting events involving long durations, high intensity work, and those in hot climates.

Military training

The Military Health System and Defense Health Agency reported 1,812 cases of exertion-related hyponatremia between 2008 and 2023 among active service members.

The symptoms of hyponatremia can be misinterpreted as those of dehydration, meaning that accurate diagnosis and appropriate treatment are essential.

For example, a 2015 report found that excess water consumption during a hot-weather 40-kilometer marching exercise caused a fatal outcome rather than prevented it. The soldier in question consumed almost 13 L of water during the exercise when peers drank closer to 10 L.

Mental health conditions

Compulsive water drinking, also called psychogenic polydipsia, can be a symptom of various mental health conditions.

It is most common among people with schizophrenia, but it can also arise in people with affective disorders, psychosis, and personality disorders.

»Polydipsia: Why am I always thirsty?

Drug interactions

Some drugs, such as MDMA, can also cause extreme thirst, which may lead to over-drinking water.

Some diuretics and vasopressors can also increase a person’s risk of hyponatremia.

Frequently asked questions

Can too much water be fatal?

It is difficult to consume too much water by accident. However, in rare instances, it can lead to fatal complications.People at risk of death from water intoxication tend to be participating in endurance sporting events, military training, or other high-exertion undertakings.

It is difficult to consume too much water by accident. However, in rare instances, it can lead to fatal complications.

People at risk of death from water intoxication tend to be participating in endurance sporting events, military training, or other high-exertion undertakings.

How much water is too much?

The kidneys can eliminate about one liter of water per hour.

To avoid hyponatremia, it is important not to outpace the kidneys by drinking more water than they can eliminate.

How much water do you need?

According to the Centers for Disease Control and Prevention (CDC), there are no official guidelines about how much water a person needs to drink each day.The right amount differs, depending on factors such as body weight, level of physical activity, climate, and whether they are chestfeeding.

According to the Centers for Disease Control and Prevention (CDC), there are no official guidelines about how much water a person needs to drink each day.

The right amount differs, depending on factors such as body weight, level of physical activity, climate, and whether they are chestfeeding.

Summary

Drinking too much water can lead to water intoxication. This is rare and tends to develop among endurance athletes and soldiers.

There are no official guidelines about how much water to drink. To avoid water intoxication, some sources recommend drinking no more than one liter of water per hour.

Nutrition / Diet
Urology / Nephrology
Environment / Water / Pollution

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Almond CSD, et al. (2005). Hyponatremia among runners in the Boston Marathon.https://www.nejm.org/doi/10.1056/NEJMoa043901
Bhatia MS, et al. (2017). Psychogenic polydipsia — management challenges.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5579464/
Buck E, et al. (2023). Exercise-associated hyponatremia.https://www.ncbi.nlm.nih.gov/books/NBK572128/
Elkattawy S, et al. (2021). Methylenedioxymethamphetamine (MDMA)-induced hyponatremia: Case report and literature review.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232921/
Exertional hyponatremia among active component members of the U.S. Armed Forces, 2008–2023.https://pmc.ncbi.nlm.nih.gov/articles/PMC11107843/
Fast facts: Data on water consumption. (2024).https://www.cdc.gov/nutrition/php/data-research/fast-facts-water-consumption.html?CDC_AAref_Val=
Hyponatremia (low sodium level in the blood). (2023).https://www.kidney.org/kidney-topics/hyponatremia-low-sodium-level-blood
Lee LC, et al. (2016). When plenty is too much: water intoxication in a patient with a simple urinary tract infection.https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC5129180&blobtype=pdf
Nolte HW, et al. (2015). Exercise-associated hyponatremic encephalopathy and exertional heatstroke in a soldier: High rates of fluid intake during exercise caused rather than prevented a fatal outcome.https://pubmed.ncbi.nlm.nih.gov/25586818/
Peechakara BV, et al. (2023). Water toxicity.https://www.ncbi.nlm.nih.gov/books/NBK537231/
Rondon H, et al. (2023).Hyponatremia. https://www.ncbi.nlm.nih.gov/books/NBK470386/
Shanmugalingam A. (2022) Use of clozapine to treat psychogenic polydipsia in schizoaffective disorder—A case report.https://www.sciencedirect.com/science/article/pii/S2773021222000554

Share this article

Medically reviewed by Adrienne Seitz, MS, RD, LDN, Nutrition — Written by Arlene Semeco, MS, RD — Updated on April 10, 2025

Latest news

ADHD Drugs Like Adderall May Work Differently Than Previously Thought
Body clock disturbances may contribute to dementia risk, evidence suggests
10 minutes of intense exercise may help treat colorectal cancer
Hot flash treatment can slow breast cancer growth, trial finds
Wegovy pill: How does it compare to injections and what are the side effects?

Related Coverage

How much water you need to drinkMedically reviewed by Stacy Sampson, D.O.
Water is important for maintaining a healthy temperature, lubricating joints, and enhancing digestion. Dehydration can be dangerous, and too much…
READ MORE
What you should know about dehydration
Dark-colored urine and thirst are common signs that someone is dehydrated. Read more about the symptoms, complications, treatment, and prevention of…
READ MORE
Is drinking cold water bad for a person?
Drinking enough water is vital to health and good bodily functioning. Some sources suggest that the temperature of the water a person drinks is also…
READ MORE
How much water should you drink a day?
Find out more about how much fluid the body needs every day, how the body balances its fluid, and more.
READ MORE
Does alcohol dehydrate you?Medically reviewed by Debra Sullivan, Ph.D., MSN, R.N., CNE, COI
Alcohol has a dehydrating effect on the body, especially when a person consumes it in large amounts. Learn more.
READ MORE

Tag » How Much Is 4l Of Water

Health Conditions

Health Products

News

Original Series

Podcasts

General Health

Health Tools

Quizzes

About Medical News Today

Find Community

Follow Us