What Happens to Your Body When You Drink Too Much Water?

Written by Angela Dunn, MD, MPH | Reviewed by Katie E. Golden, MDUpdated on July 17, 2023

Key takeaways:

• Drinking too much water can be dangerous when it leads to low sodium levels in the blood. This is called hyponatremia, and severe cases can be life-threatening. 
• This is rarely a problem for healthy people. But it can happen to athletes during intense exercise. People with heart or kidney problems are also at higher risk of overhydration.
• You need to drink water to stay hydrated, but it’s best not to overdo it and drink more than you need.

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There is such a thing as having too much water in your body, as strange as that may seem. It doesn’t happen very often, though. Having too little water, or dehydration, is much more common. Overhydration, sometimes called water intoxication or water poisoning, happens when you have too much water in your body. And, in some cases, it can pose a serious health risk.

What happens if you drink more water than you should?

Having more water in your body than you should is called overhydration. People who don’t have any serious medical conditions usually don’t have to worry about drinking too much water. Healthy kidneys can adjust how much water leaves the body as urine. The kidneys make sure the body keeps the amount of water it needs and gets rid of the excess water it doesn’t need. On average, a healthy person would have to drink more than 6 gallons a day to develop overhydration.

But some people can become overhydrated more easily. This can have serious consequences because it causes an imbalance of electrolytes. Examples of electrolytes are sodium, potassium, and calcium. They help keep important parts of your body functioning normally, like your heart, blood, and brain. Electrolytes are also vital for your nerves and muscles. So, overhydration is a problem because it can dilute the electrolyte levels in your blood.

You may be at higher risk for overhydration if you have a medical condition that causes you to:

• Retain fluid, like heart or liver failure
• Increase your intake of fluid
• Take medications that affect how your kidneys handle fluid

Can drinking too much water be dangerous?

Drinking too much water can be dangerous in some cases. It can even cause death. The greatest risk from overhydration is hyponatremia. This is when the sodium in your blood is too low. It can happen when someone drinks so much water that it dilutes the sodium level in their body to abnormally low levels.

Overhydration can occur in healthy individuals, especially athletes. This is more likely to happen during intense or prolonged exercise, when sodium leaves the body through sweat. If someone then drinks a lot of water, it can cause sodium levels to drop quickly. This is called exercise-associated hyponatremia.

As mentioned above, sodium is an electrolyte that plays an important part in how your heart and brain function. Low sodium not only disrupts normal body function, but it can cause serious swelling in the brain, too. When the sodium level drops slowly, your body has time to adjust, so you may not have any symptoms. But when hyponatremia happens more quickly, mild to severe symptoms can occur that require medical attention. 

What are common symptoms of drinking too much water?

Early warning signs of overhydration can look like a lot of different things, such as heat exhaustion or a stomach bug. Symptoms include: 

• Nausea or vomiting
• Headache
• Loss of energy
• Muscle cramps 

If hyponatremia happens quickly and is left untreated, severe symptoms can develop that require immediate medical attention. These include:

• Confusion
• Seizures
• Coma

How much water should you drink each day?

Many people may remember the old recommendation of 8 glasses or about 2 L of water per day. This is not recommended anymore because most people actually get enough water from the foods they eat and the liquids they drink throughout the day. For example, eating fruits and vegetables and drinking liquids that contain water, like coffee or tea, all contribute to your hydration. 

The amount of water you should drink to stay hydrated is affected by your:

• Age
• Sex
• Medical conditions
• Physical activity

For many people, drinking water when you feel thirsty may be enough. The color of your urine can also be a sign of how well hydrated you are. Clear or light-yellow urine usually means you are well hydrated. But dark-yellow or amber urine may mean you need to drink more water. And brown urine is usually a more concerning sign that there is another medical problem that needs attention. 

What kind of situations put someone at risk of drinking too much water?

There are a few different situations that can put someone with healthy kidneys at risk of drinking too much water. Drinking a lot of water in a short amount of time — like during extreme physical activity or as a way to treat a different medical problem — can cause overhydration. Increasing your water intake regularly over a longer time period can also lead to overhydration.

There are case reports of people who developed overhydration from drinking water to:

• Prevent dehydration from a gastrointestinal (GI) bug
• Avoid a urinary tract infection (UTI) or kidney stones
• Treat constipation or poison ingestion
• Get ready for an athletic competition
• Lose weight or feel healthier

Some people have medical conditions that put them at high risk of overhydration. This is because their kidneys cannot get rid of water normally or their bodies tend to retain water. In these cases, overhydration can be a serious problem. Examples of these conditions include:

• Kidney failure
• Heart or liver failure
• Syndrome of inappropriate antidiuretic hormone (SIADH)

In some cases, antidepressant medications, like selective serotonin receptor inhibitors (SSRIs) can lead to overhydration. So can some mental health conditions, like depression, bipolar disorder, and schizophrenia.

If people at risk of overhydration drink more water than their body needs, they can develop:

• High blood pressure
• Shortness of breath
• Bloating
• Leg swelling

Can overhydration be treated?

Overhydration can be treated. If you are otherwise healthy and have mild symptoms, simply cutting back on the amount of fluid you are drinking will do the trick. You should start to feel better in a few hours. 

If you have more serious symptoms, such as confusion, you need to seek medical attention immediately. Healthcare providers will test how much sodium is in your blood and give you a salt-water solution through your veins. The providers will closely watch you to make sure you are getting better. They will also test how much sodium is in your blood every few hours. With early detection and treatment, you can fully recover from overhydration.

The bottom line

For people with healthy kidneys, drinking a lot of water is not usually a problem. People with certain medical conditions may be at risk of overhydration. But this can happen to healthy people, too. Athletes are at risk for overhydration when they drink a lot of fluids during intense exercise. Overhydration may cause uncomfortable symptoms. But it can also cause severe and fatal consequences. Drinking enough water to stay hydrated is important for your health. But be careful not to overdo it.