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What is overhydration?

All of the major systems of your body depend on water to work properly. Drinking adequate amounts of water helps your body:

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

Most people, especially those who exercise in hot weather, are more concerned about not drinking enough water. However, drinking too much water can also be dangerous.

Overhydration can lead to water intoxication. This occurs when the amount of salt and other electrolytes in your body become too diluted. Hyponatremia is a condition in which sodium (salt) levels become dangerously low. This is the main concern of overhydration.

If your electrolytes drop too low too quickly, it can be fatal. Death by overhydration is rare, but it can happen.

There are two main types of overhydration:

Increased water intake

This occurs when you drink more water than your kidneys can remove in your urine. This can cause too much water to collect in your bloodstream.

Retaining water

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

Both of these types are dangerous because they throw off the balance between water and sodium in your blood.

Overhydration is an imbalance of fluids. It happens when your body takes in or holds on to more fluid than your kidneys can remove.

Drinking too much water or not having a way to remove it can cause water levels to build up. This dilutes important substances in your blood. Endurance athletes, such as those who run marathons and triathlons, sometimes drink too much water before and during an event.

The Institute of Medicine established guidelines for adequate water intake. They recommend that a healthy adult drink 78–100 ounces (about 9­–13 cups) of fluids per day, on average.

It’s also important to remember that water needs vary with age, sex, weather, activity level, and overall health. So there is no exact formula on how much to drink. Common situations such as extreme heat, significant activity, and illness with fever will all require more fluid intake than average.

In a healthy person, your urine is a good indicator of your hydration status. Pale yellow urine that looks like lemonade is a good goal. Darker urine means you need more water. Colorless urine means you are overhydrated.

In healthy people, athletes are at highest risk for overhydration. Sports experts at Harvard recommend that a logical approach to hydration while exercising is letting thirst be your guide.

Some conditions and medicines cause overhydration by making your body hold on to more fluid. These include:

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

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.

You may not recognize symptoms of overhydration in its early stages. As the condition progresses, common symptoms include:

Untreated overhydration can lead to dangerously low levels of sodium in your blood. This can cause more severe symptoms, such as:

Your doctor will ask about your medical history to find out if your symptoms are caused by overhydration or another condition. The doctor will also perform a physical examination, and they may order blood and urine tests.

How you’re treated for overhydration depends on how severe your symptoms are 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 overhydration by weighing themselves before and after a race. This helps determine how much water they have lost and need to replenish. It is recommended to drink 16 to 20 ounces of fluid for every pound lost.

While exercising, try to drink 2 to 4 cups of fluid per hour. If exercising longer than an hour, sports beverages are also an option. These drinks contain sugar, along with electrolytes such as sodium and potassium, which you lose in sweat. Let thirst also guide you when exercising. If you’re thirsty, drink more.

Shop for sports beverages.

If you have a medical condition such as diabetes, CHF, or kidney disease, talk to your doctor about the best treatments. Also contact your doctor if you’re unusually thirsty. This could be a sign of a medical problem that needs to be treated.