Overhydration Symptoms + Helpful Tips To Prevent It In The First Place

As runners, we are typically concerned with dehydration. We worry that we aren’t taking in enough fluids during our training or as we go about our day. Therefore, we ensure we drink plenty of water throughout the day and take in fluids during our intervals, long runs, and races.

Dehydration can occur for runners during races or even day-to-day training. However, we should also be aware of overhydration and overhydration symptoms, as they can also cause issues for runners.

A large portion of our body is made up of water, an adult male is composed of about 60% water, so it stands to reason that we need a lot of water to ensure that our body is able to function at its optimal level. 

As with most things, there can be too much of a good thing. Drinking too much water can lead to overhydration which can, in turn, lead to severe consequences.

So what can we do to make sure we don’t fall into the overhydration trap? What signs should we look for in ourselves or training partners to ensure we aren’t experiencing overhydration symptoms? Keep reading to find out!

In this article, we will discuss the following:

  • What Is Overhydration?
  • Overhydration Symptoms and Signs
  • Who Is At Risk For Overhydration?
  • How To Fix Overhydration
  • How To Prevent Overhydration
A runner drinking from a water bottle.

What Is Overhydration?

Overhydration is also known as water intoxication, water poisoning, hyperhydration, or water toxemia.

Overhydration is caused by the body taking in more fluid than it can remove. This can occur in endurance athletes who are focused on getting in lots of fluids, so they don’t dehydrate or people whose bodies retain fluid through lack of sweating or issues with their kidneys, livers, or pituitary glands.

Sodium is an electrolyte; one of its functions is to help the body keep fluids in balance. The buildup of fluid in the body decreases sodium levels which can be harmful and cause a range of medical issues.

Endurance athletes like marathoners and triathletes are the most likely to suffer from overhydration when compared to other healthy individuals. This is due to consuming a lot of fluid before and during an event which can lead to overhydration if the kidneys cannot remove the fluid quickly enough.

A runner drinking from a water bottle.

A study from 2015 found that there were instances of overhydration in 13-15% of finishers in two long-distance running events. The article states that distance runners are more prone to overhydration than dehydration.

Of the 887 finishers of a 100-mile race in Northern California, 15.1% were reported to have exercise-associated hyponatremia or overhydration symptoms.

At the 2002 Boston Marathon, 13% of 488 runners had hyponatremia, and .06% had critical cases after finishing the race.

It’s important to note that the amount of water your body can process each day can vary based on a lot of different factors. Sex, weight, weather, activity level, and health can all dictate the amount of water we should be drinking and what our bodies are able to process.

That being said, the Mayo Clinic recommends the average male drink just over 3.5 liters of water a day and the average female drink just over 2.5 liters a day.

I would also like to state that I am not a medical professional, and the information in this article should not be taken as medical advice. If you feel you or someone else might be suffering from dehydration or overhydration, seek medical attention.

With all that in mind, let’s learn about overhydration.

A runner with a headache.

Overhydration Symptoms and Signs

There are several signs and symptoms of overhydration.

The easiest and most likely first indicator is your urine.

Monitoring the color of your urine during endurance events can tell you a lot about your hydration levels. Urine that is dark yellow or even brownish in color can let you know that you are dehydrated. Similarly, clean urine can let you know that you could potentially be overhydrating.

Having urine pale yellow in color is typically a good benchmark to base things on.

If you find yourself having to urinate more than you usually do, it could be an early indicator that you are overhydrated. 

More severe overhydration symptoms may include:

  • Headaches
  • Nausea
  • Becoming disoriented or confused
  • Muscle cramps
  • Tiredness or fatigue
  • Swollen feet, hands, and lips

These can often be a bit confusing because several of these symptoms of overhydration are also symptoms of dehydration.

A runner holding their chest.

Headaches are caused by excess fluid and lower sodium levels, causing cells to swell. Nausea, vomiting, and diarrhea can also occur because of this.

The lower sodium in your blood caused by the excess of water can lead to a dip in energy. This can lead to fatigue or a constant feeling of being tired in an individual.

The lower sodium levels mean that there are lower levels of electrolytes in the body. This can cause swelling in the hands, feet, and lips.

Muscle cramps or tiredness/fatigue can be difficult to diagnose because you could be experiencing these during endurance events just because of your effort and exertion.

Eventually, the excess water can cause your brain cells to swell. The swelling will cause issues with your nervous system, and it will malfunction.

This can lead to high blood pressure and low heart rate. High blood pressure and a low heart rate can cause seizures, a coma, or even death can occur if these symptoms are left untreated.

Death is rare, particularly in athletes who are otherwise healthy. It’s often a combination of too much fluid paired with a medical issue or disorder that causes the kidneys to retain that fluid. However, overhydration should still be taken seriously by anyone who is experiencing symptoms.

A person running on the road.

Who is at risk Of overhydration?

Overhydration is common among individuals who drink large amounts of water or liquid before and during king bouts of exercise.

Marathoners, ultramarathoners, triathletes, cyclists, rugby players, rowers, military members, and hikers are at an elevated risk.

We tend to drink large amounts of water leading up to endurance events to ensure we are hydrated.

A lot of people also follow the advice of drinking before they are thirsty to stay ahead of dehydration. Both of these can actually contribute to overhydration.

The risk is elevated for individuals with kidney or liver disease or who have heart failure. Those individuals should pay special attention to the symptoms and be aware of how they are feeling during races.

The word electrolytes and a stethoscope.

How to fix overhydration

The treatment of overhydration can depend on the severity of the case. This could range from managing on your own to seeking medical attention.

Minor cases might be solved simply by cutting back on fluid intake or taking diuretics to increase urine production. More advanced cases may include treating the conditions that led to overhydration, such as kidney or liver disease.

Some medications may increase the risk of overhydration, which may mean that a medical professional will decide to have you stop taking them.

In severe cases, you might have to get sodium replaced to bring your body back to equilibrium.

The good news is that most cases are mild and will likely subside in a matter of hours with a reduction in fluid intake.

A runner drinking from a water bottle.

How to prevent overhydration

As the saying goes, an ounce of prevention is worth a pound of cure. So how can we prevent overhydration in the first place?

A common practice to help prevent dehydration can also be used to prevent overhydration.

Taking a sweat test (weighing yourself before and after longer endurance outings) can help you determine the rate your body loses fluids. This can help you understand how much you should be replacing on an hourly basis.

You’ll often hear that you should let your thirst guide you when to drink. If you are thirsty, drink some water or a sports drink. If not, don’t drink anything.

While this rule might not work in all weather or environments, it is a good rule to follow outside of the extremes. If you find yourself in a warmer climate or at a high altitude, you may need to adjust your fueling to stay at homeostasis.

A runner sweating, hunched over.


It’s important to practice fueling, whether with food or fluids, during workouts and long runs so you will have an idea of what your body handles best on race day.

Having a set cadence of when you will be taking in fluids or food can not only help keep you from having an upset stomach or bonking, but it can help ensure you are not in danger of overhydrating or being dehydrated.

As mentioned, while most runners are concerned with dehydration, we’ve seen that overhydration can also be something that we should keep an eye on. Watching for signs of overhydration and being mindful of how much fluid we are taking in can help keep us going during long bouts of exercise.

Did you know overhydration was more prominent in endurance events than dehydration? Now that you know what the signs of overhydration are, what steps will you take at your next race to help mitigate overhydration?

To work on your fueling strategy, check out our article: How To Fuel For A Marathon: What To Eat Before, During, And After Your Race.

Two runners holding water bottles.
Photo of author
Adam Rabo has been running since junior high. He has coached high school and college distance runners. Adam recently completed the UTMB Canyons 100k, making the cutoff for the Western States 100 and UTMB. You can generally find him on the rodes or trails in Colorado Springs, training for upcoming marathons and ultramarathons.

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