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Most people, especially those who exercise in hot weather, are concerned about not drinking enough water. But drinking too much water can also be dangerous. Some conditions can also make your body retain too much water, regardless of how much you drink.

All of the major systems of your body depend on water to work properly. Having enough water helps your body:

  • regulate temperature
  • prevent constipation
  • flush out waste products
  • perform all major bodily functions

However, it’s possible to have too much water in your body. This can cause water toxicity. This is when your body’s water is more than your kidneys can excrete. It can lead to a dangerous electrolyte imbalance.

Read on to learn how this can happen, how much water is too much, how to recognize the signs, and what to do.

You can become overhydrated in two ways: By drinking too much water or if your kidneys retain too much water.

In both cases, overhydration can lead to water toxicity, also known as water poisoning. Your body’s water volume becomes too large for your kidneys to excrete, which can cause the electrolytes in your body to dilute.

When the amount of sodium (salt) becomes too diluted, you develop hyponatremia. This is the main concern of overhydration. When the sodium levels in your body are greatly reduced, fluids move inside your cells, leading to inflammation.

Increased water intake

This occurs when you drink more water than your kidneys can remove from your urine. Endurance athletes, such as those who run marathons and triathlons, sometimes drink too much water before and during an event. In healthy people, athletes are at the highest risk for overhydration.

Certain conditions and drugs can also cause increased water intake by making you extremely thirsty. These include:

Retaining water

This occurs when your body can’t get rid of water properly. Several medical conditions can cause your body to retain water. These include:

The Institute of Medicine has established guidelines for adequate water intake. They recommend that a healthy adult drink 78–100 ounces (oz) (about 9­–13 cups) of fluids per day on average. It’s also important to remember that the food you eat, such as vegetables or fruit, also contains water.

That being said, the amount of water you need to drink can vary and should roughly equal the amount your kidneys release. Children and adolescents may have lower requirements than adults.

It’s also important to remember that water needs vary with sex, weather, activity level, and overall health. Common situations such as extreme heat, significant activity, and illness with fever may require more fluid intake than average.

You may not recognize symptoms of overhydration in its early stages. However, urine is a good indicator of hydration status in a healthy person.

Pale yellow urine that looks like lemonade is a good goal. Darker urine means you need more water. Colorless urine means you are overhydrated.

If you get hyponatremia from water toxicity, you’ll likely experience the following:

Ultimately the swelling of brain cells will cause your central nervous system to malfunction. Without treatment, you can experience seizures, enter into a coma, and ultimately die.

Death from drinking too much water in healthy people is rare, but it can happen, especially in athletes. Usually, water toxicity occurs along with an underlying medical condition that causes the kidneys to retain fluid.

Can drinking too much water be fatal? Learn more.

Water toxicity from overhydration is more common among endurance athletes who drink large amounts of water before and during exercise. It has been reported among:

  • people who run marathons and ultramarathons (races longer than 26.2 miles)
  • ironman triathletes
  • endurance cyclists
  • rugby players
  • elite rowers
  • military members involved in training exercises
  • hikers

This condition is also more likely in people with kidney or liver disease. It can also affect people with heart failure.

A doctor will ask about your medical history to determine if your symptoms are caused by water toxicity, hyponatremia, or another condition.

The doctor will also perform a physical examination, and they may order blood and urine tests to check the level of sodium and other markers in your body.

They may observe you for a time to see how much fluid you are taking in versus how much you release in urine or stool. They may measure your weight to watch for changes indicative of insufficient fluid loss.

If you have more obvious water toxicity symptoms, the doctor may identify these sooner and initiate treatment.

How you’re treated depends on whether you show symptoms of water toxicity and what caused the condition. Treatments may include:

  • cutting back on your fluid intake
  • taking diuretics to increase the amount of urine you produce
  • treating the condition that caused the overhydration
  • stopping any medications causing the problem
  • replacing sodium in severe cases

Endurance athletes can reduce the risk of water toxicity from overhydration by weighing themselves before and after a race. This helps determine how much water they have lost and need to replenish.

While there are different guidelines, they generally recommend drinking 14-22 oz of fluid about two-three hours before exercise or physical activity.

If exercising longer than an hour, sports beverages are also an option. These drinks contain sugar and electrolytes such as sodium and potassium, which you lose in sweat. Let thirst also guide you when exercising. If you’re thirsty, drink more.

However, if you are an endurance athlete or planning on starting an endurance training program, you want to talk with your doctor to get hydration advice tailored specifically to you.

The following are the answers to some common questions about overhydration.

How much water a day is overhydration?

Healthy adult kidneys can eliminate about 1 liter (l) or 0.2 gallons (gl) of water per hour. Although no specific amount of fluids can cause overhydration for a person, it’s a good idea not to drink more than your kidneys can handle.

Kidneys of children and older people may be less efficient at removing water, so you should consult with a primary care doctor or pediatrician to understand the appropriate amount. Some doctors recommend that the number of daily cups of water a child drinks should equal their age.

Can overhydration cause permanent damage?

Drinking too many fluids can cause water toxicity by diluting your body’s sodium and other electrolytes, which may cause your cells to swell, including the cells in your brain. This is a life threatening condition. If left untreated, it may cause permanent brain damage and death.

How long does it take to recover from overhydration?

Your recovery will depend on the severity of your symptoms. If you progress to water toxicity, you will need to be hospitalized. If you experience any symptoms associated with overhydration, contact your doctor.

Overhydration due to drinking too much water causes water toxicity, an electrolyte imbalance that can cause symptoms ranging from nausea and headache to unconsciousness and coma.

To avoid overhydrating, try to drink no more than about 9­–13 cups of fluids per day. If you have a medical condition such as diabetes, CHF, or kidney disease, talk with your doctor about the best treatments.

Also, contact your doctor if you’re unusually thirsty. This could signify a medical problem that needs to be treated.