Can Drinking Too Much Water Be Harmful?

By: Kelechi Nwaowu, RN, RM. Freelance Health and Wellness Writer.  Medically reviewed by: Swabirah Sulaiman, BSc. Physiology. Clinical Physiologist. 

May 25, 2026

AI-generated image of an African woman pouring a bottle of water into a glass cup.  Image Credit: Gemini AI 

 

Highlights

• When it happens, short or long-term excessive drinking of water can cause a serious and potentially dangerous condition known as water intoxication (also called water poisoning or overhydration).

• Water intoxication dilutes the sodium (salt) in your blood to very low levels, causing a condition called hyponatremia (low sodium in blood).

• When sodium levels drop too low, water moves into your body's cells and makes them swell. When brain cells swell, it increases pressure inside your skull, leading to headache, confusion, irritability, seizures, coma, and even death.

• Between 2008 and 2023, the US Military Health System reported 1,812 cases of exercise-related hyponatremia among active service members, showing that drinking too much water during intense physical activity is a real danger.

• Babies under 6 months old should never be given water, not even in hot weather. Their kidneys cannot process water properly, hence drinking water can readily cause water intoxication and malnutrition.

• The "8 glasses of water a day" rule is a myth. There is no official guideline about how much water everyone should drink because the right amount differs based on your body size, activity level, climate, and health conditions.

 

Introduction

Chioma had just registered with a gym facility, and her trainer had told her class to drink plenty of water to stay hydrated. Chioma took this advice seriously, and for the past 12 days, she has been drinking lots of water. She forces herself to finish at least eight 75cl bottles of water in a day, which is 6 liters of water daily.

During her Saturday morning workout, her trainer kept on saying, "Stay hydrated!" as they ran laps around the field. Chioma picked up her can and drank a full bottle of water before the workout, another during their 20-minute run, and two more bottles afterward.

By the time she got home, Chioma felt strange. Her stomach was bloated and uncomfortable, with a pounding and dull headache. When she tried to eat lunch, she felt sick and she threw up. "Maybe I pushed too hard during exercise," she thought.

However, the symptoms got worse with time. Chioma started experiencing confusion, and her hands and feet started swelling. Her worried family quickly rushed her to the hospital, where she was diagnosed with water intoxication. Chioma had drunk so much water that it dangerously lowered the salt level in her blood, causing her brain to swell.

Most people know that not drinking enough water is unhealthy, but can drinking too much water be harmful? The answer is yes, and it can be just as harmful or as not drinking enough.

Read on to learn more about water intoxication or overhydration

 

The Importance of Water

Water is the foundation of life, and it is the most important part of your body. While we think of ourselves as solid, we are actually made mostly of water. As a healthy adult, water makes up about 70 to 75% of your lean body mass – which includes your muscles and organs (1). Even your bones, as hard as they feel, are made of about 30% water.

Because water is in every cell, it keeps you healthy in so many ways. 

Water hydrates and nourishes your body, removes waste through sweat and urine, prevents kidney stones, supports healthy skin, aids digestion, and maintains normal body temperature (1). Without water, none of these functions would work, and life would be impossible.

When you do not drink enough water, you become dehydrated. Dehydration causes headaches, dizziness, dry mouth, dark yellow urine, and tiredness. Severe dehydration can damage your kidneys and even threaten your life.

Because of the harmful effects of not drinking enough water, healthcare professionals, fitness trainers, and health websites tell you to drink water regularly. The message "drink more water" is everywhere, but there is another side to this story that people rarely talk about, overhydration or water intoxication.

For more on the importance of water, read: 10 Health Benefits of Drinking Water  

 

What is Water Intoxication?

Water intoxication or overhydration is a serious medical condition that happens when you drink too much water, which causes an imbalance in your body's electrolytes (minerals like sodium that help your cells work properly) (2).

When you drink a normal amount of water, your kidneys filter out the extra water and remove it through urine; however, the kidneys can only process about 0.8 to 1 liter of water hourly (3).

If you drink more water than your kidneys can handle at a time, the excess water stays in your body and dilutes your blood.

 

What Happens When You Drink Too Much Water?

AI-generated illustration of what happens when you drink too much water.  Image Credit| Gemini AI. Click on image to enlarge.

 

Think of your blood like soup. This soup needs the right balance of ingredients – water and minerals like sodium (salt) – for healthy living. When you drink too much water, it is like pouring gallons of water into a pot of soup. The soup becomes watery and tasteless because the water has diluted all the other ingredients.

In your body, this watery state leads to a medical condition called hyponatremia. Hyponatremia means having too little sodium (salt) in your blood (“hypo” means low, and “natremia” means sodium in the blood). Doctors diagnose hyponatremia when the sodium level in your blood drops below 135 millimoles per liter (mmol/L) (3).

When this happens, your body cells notice that the liquid outside them (your blood) now has less salt than the liquid inside them. So to balance things out, water moves from your blood into your cells, trying to even out the salt levels.

This movement of water from outside the cell to inside causes your cells to swell like balloons filling with water (2). Most cells can handle some level of swelling, but brain cells are trapped inside your hard skull with no room to expand. Hence, the swelling of the brain cells builds up pressure inside your head, which slows brain function and causes the symptoms of water intoxication (2).

 

Signs and Symptoms of Water Intoxication

AI-generated infographic on the Signs and Symptoms of hyponatremia. Image Credit: Gemini AI. Click on image to enlarge. 

 

The symptoms of water intoxication can appear gradually or suddenly, depending on the pace and quantity of water taken. Early symptoms often look similar to dehydration symptoms, which makes water intoxication confusing to diagnose (2).

Early Warning Signs 

The first signs of water intoxication usually include:

• Nausea and vomiting: Your stomach feels upset, and you may throw up.

• Headache: A dull, persistent headache develops as pressure begins building in your skull.

• Bloated stomach: Your belly feels uncomfortably full and swollen.

• Muscle weakness: Your muscles feel tired and weak, even if you have not exercised much.

• Muscle cramps: Your muscles may cramp or twitch.

• Confusion: You have trouble thinking clearly, feel disoriented, or cannot concentrate.

• Irritability: You feel unusually grumpy or agitated for no clear reason.

Many people who develop these symptoms assume they are dehydrated and drink even more water, making the problem worse (3). This is why recognizing water intoxication early is so important.

Severe Symptoms

If water intoxication is not caught and treated early, the symptoms become much more serious and life-threatening. The seriousness is often shown by the following signs and symptoms (2):

• Drowsiness: The person becomes extremely sleepy and has trouble staying awake.

• Severe confusion and disorientation: They cannot think clearly, do not recognize people or places, and may say things that make no sense.

• Swelling (edema): Hands, feet, and face swell noticeably.

• Difficulty breathing: Breathing becomes labored or fast.

• Seizures: The brain pressure causes sudden, uncontrolled electrical activity in the brain. The person's body stiffens and shakes violently.

• Coma: The person becomes completely unconscious and cannot be awakened.

• Death: In the most severe cases, water intoxication can be fatal. The pressure inside the skull compresses vital brain structures that control breathing and heart rate.

A tragic case in 2007 involved Jennifer Strange, who died after drinking nearly 2 US gallons (7.6 liters) of water in an attempt to win a Nintendo Wii console in a radio station contest (4). Her death brought national attention to the dangers of water intoxication.

 

Who is at Risk of Drinking Too Much Water (Water intoxication)?

Water intoxication is rare, so it does not happen to everyone. For most healthy people with normally functioning kidneys, it is very difficult to drink yourself into water intoxication accidentally (2). But certain groups of people face higher risks.

1. Athletes and Marathon Runners

Marathon runners, cyclists, hikers, and other endurance athletes like soldiers in training are at the highest risk of water intoxication (3). During long periods of intense exercise, they sweat heavily, and this sweat contains water and salt. When they lose sweat, they lose both the salt and the water.

However, many athletes have been taught to drink as much water as possible during exercise to avoid dehydration. Following this advice, some athletes drink large amounts of plain water without replacing the salt they have lost. This creates an imbalance in the blood where the water is more than the salt.

Between 2008 and 2023, the United States Military Health System reported 1,812 cases of exertion-related hyponatremia (low sodium from exercise) among active service members (3). A 2015 military report described a soldier who died during a 40-kilometer marching exercise in hot weather. He drank almost 13 liters of water during the exercise, while his peers drank closer to 10 liters. The excess water caused rather than prevented his fatal outcome (5).

Military training guidelines now recommend that soldiers drink no more than 1 to 1.5 liters of water per hour during heavy sweating (3).

2. People with Certain Medical Conditions

The following medical conditions make it easier to develop water intoxication:

• Mental health conditions: People with schizophrenia sometimes develop a condition called psychogenic polydipsia, which means they feel compelled to drink excessive amounts of water even when they are not thirsty (2). This is the most common non-athletic cause of water intoxication.

• Kidney disease: If the kidneys do not work as they should, they cannot remove extra water from the body efficiently. This means water easily builds up in the body (2).

• Heart failure: When the heart is weak, the body often retains extra fluid, making it easier to develop hyponatremia with continuous water intake.

• Diabetes insipidus: This rare condition makes people extremely thirsty, and as a result, they may drink large amounts of water.

• Certain medications: Some psychiatric medications, including certain antidepressants (drugs that help to improve mood) and antipsychotics (drugs used to help keep people grounded in reality and have less disturbing thoughts), can cause the body to retain water or trigger excessive thirst (2).

3. Infants: A Special Risk

Babies, especially those under 6 months old, are extremely sensitive to water intoxication (6). Their small bodies and immature kidneys cannot handle extra water the way adult bodies can.

Because a baby's kidneys are still developing, they cannot filter and remove water as efficiently as adult kidneys. So, when a baby drinks water, even a small amount can dilute their blood and cause a sodium imbalance.

This higher risk of developing water intoxication is one of the reasons why the WHO advises that babies under 6 months old should be given only breastmilk (6, 7).

Some families believe they should give babies water in hot weather to prevent dehydration. This is wrong because breast milk provides all the water a baby needs, even in hot climates.

Want to know about breastfeeding? Read: 6 Breastfeeding Tips for New African Moms

 

Why your Water Intake Goal Changes Every Day

There are no official guidelines from the World Health Organization about exactly how much water a person needs to drink each day (3). This is because the right amount of water is different for everyone. How much water you need depends on:

• Your body size: An adult needs more water than a child.

• Your activity level: Athletes and people who do physical work sweat more and need more water than people who sit at a desk all day.

• State of the weather: If the weather is hot and humid, you lose more water through sweat and need to drink more.

• Your health: Pregnant women, breastfeeding mothers, and people with certain illnesses need different amounts of water.

The best guide for how much to drink is to listen to your body. Drink when you feel thirsty, and check your urine color to see if you are properly hydrated. 

 

How to Properly Hydrate Without Drinking Too Much Water

Now that you understand the dangers of drinking too much water, you might feel confused about how much to drink. Proper hydration is simple when you follow these practical guidelines.

1. Listen to Your Body: Thirst as a Guide

Your body has a built-in hydration sensor for thirst. When your body needs water, it sends you a signal – you feel thirsty. This is your body's way of telling you, "Please drink some water now."

For most healthy people, thirst is a reliable guide (3). Drink water when you feel thirsty, and stop when you feel satisfied. You do not need to force yourself to drink excess water when you are not thirsty.

However, children and older adults are the exceptions. Children often get so caught up in playing that they forget to drink water, and as people age, their sense of thirst becomes less sensitive. Because of this, elderly people may not feel thirsty even when their bodies need water. If you are caring for a child or an elderly person, offer them water at different times during the day, even if they do not ask for it.

2. Use Your Urine Color as a Simple Hydration Guide

AI-generated infographic on the different urine colors and their possible meanings. Image Credit| Gemini AI. Click on image to enlarge. 

 

Your urine color is one of the best ways to check if you are drinking the right amount of water.

• Light yellow: This urine color usually means you are well hydrated.

• Dark yellow: You need to drink more water. Your urine is concentrated because your body is conserving water.

• Completely clear (like pure water): You may be drinking too much water (3). If your urine is colorless and you have symptoms like headache or nausea, stop drinking water and rest.

Check your urine color a few times during the day, especially in the morning. Morning urine is usually slightly darker because you have not had water overnight, and that is normal. The goal is to keep your urine light yellow throughout the day.

Special Considerations for Water Intake

Certain situations require you to drink more than usual:

• Hot or humid weather: When you sweat more, you need to replace the lost fluid. Drink extra water on hot days, but pace yourself. Sip water throughout the day rather than drinking huge amounts all at once.

• During and after exercise: Drink moderate amounts of water before, during, and after physical activity. For normal exercise lasting less than an hour, plain water is enough, but for intense exercise lasting more than an hour, consider drinks with electrolytes (like sports drinks) to replace lost salt (3).

• During illness, Fever, diarrhea, or vomiting: These conditions lead to loss of extra fluids. If you are showing these symptoms, drink water or oral rehydration solutions (ORS) to replace what you have lost. Sip small amounts frequently instead of gulping a full glass quickly.

• During pregnancy and breastfeeding: Pregnant women and breastfeeding mothers need more fluids than usual. Listen to your thirst, and drink enough to keep your urine light yellow.

A practical guideline by some experts suggests that you do not drink more than 1 liter of water per hour, since the kidneys filter 0.8 - 1 liter of water in an hour (3). Your kidneys need time to process the water you drink.

 

Common Myths about Drinking Water You Should Know

It is now easier to find health information online, but not all of it comes from experts and are accurate. This has led to many common misunderstandings about how much water we really need. Some of the common misunderstandings about water and hydration include the following:

Myth 1: More Water Means Better Health

More is not always better. Your body needs the right amount of water – not too little, and not too much. Drinking excessive water does not "flush out more poison" or make you healthier. In fact, it can harm you by causing water intoxication.

Myth 2: Yellow Urine Always Means Dehydration

Urine color exists on a spectrum. There are other conditions apart from the level of water intake that can affect urine color. For example, the presence of malaria parasites in the blood, liver problems, some medications and supplements.

Dark yellow urine does not always mean you need more water; it could be your body drawing your attention to an existing situation that may not be water-related. If you have been drinking enough water, you do not need to drink excessively more to clear your urine. Seek medical advice from a health professional instead, especially if you are showing other symptoms like fever, unexplained body pain, etc.

Myth 3: You Need 8 Glasses of Water Every Day 

The trending "8 glasses a day" rule is not based on scientific evidence. There is no official health guideline that says everyone must drink exactly 8 glasses (about 2 liters) of water daily (8).

The amount of water you need depends on your individual circumstances – your size, activity level, climate, diet, and health conditions. Some people may need 6 glasses, others may need 8 glasses. Let your body – thirst and urine color guide you – not an arbitrary number.

 

Conclusion

Water is essential for life; your body needs water every single day to survive and function properly. But like medicine, food, or anything else, water can become harmful when consumed in excess.

Water intoxication is rare, but it is real and can be dangerous. When you drink too much water too quickly, it dilutes the sodium in your blood, causing your cells – especially brain cells – to swell. This swelling increases the pressure inside your skull, leading to nausea or vomiting, headache, weakness. etc., and in severe cases, to confusion, seizures, coma, and even death.

Water keeps you alive, but drinking the right amount – not too much, not too little – is what keeps you healthy.

 

References:

1. Datelinehealth Africa. 10 Health benefits of drinking water. [Internet] Updated 2025 May 18. [Cited 2026 March 4]. Available from here 

2. Cleveland Clinic. Water intoxication: toxicity, symptoms & treatment. Cleveland (OH): Cleveland Clinic; 2024 Sep 17 [Cited 2026 Mar 4]. Available from here 

3. ?Semeco A. What happens if you drink too much water? Medical News Today [Internet]. 2022 Oct 9 [updated 2025 April 10; [Cited 2026 Mar 3]. Available from here 

?4. Clarke S, McHugh R. Jury rules against radio station after water-drinking contest kills Calif. mom. ABC News [Internet]. 2009 Nov 2 [Cited 2026 Mar 06]. Available from here.

5. Nolte HW, Hew-Butler T, Noakes TD, Duvenage CS. Exercise-associated hyponatremic encephalopathy and exertional heatstroke in a soldier: High rates of fluid intake during exercise caused rather than prevented a fatal outcome. Military Medicine. 2015 Jan;180(1):e152-5. Available from here.

6. Suzan ÖK, Kaya Ö, Kolukisa T, Koyuncu O, Tecik S, Çinar N. Water consumption in 0-6-month-old healthy infants and effective factors: A systematic review. Biomédica. 2023 Jun;43(2):181-99. Available from here.

7. World Health Organization. Infant and young child feeding [Internet]. Geneva: World Health Organization; 2023 [Cited 2026 Mar 04]. Available from here.

8. Valtin H. "Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 x 8"? Am J Physiol Regul Integr Comp Physiol. 2002 Nov;283(5):R993-1004. Available from here.

 

Related: 10 Health Benefits Of Drinking Water

 

 

Published: May 25, 2026

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