The Effects Of Drinking Too Much Water During Exercise


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The effects of drinking too much water are not publicized often in the mainstream media. Have you seen articles on the topic in magazine you’ve read lately…probably not. Usually it’s only after a hospitalization or death that you hear about this condition known as hyponatremia or ‘water intoxication.’

Over the last several decades runners, in particular, have heard “hydrate, hydrate, hydrate.” In previous posts I made the case for having adequate fluids onboard and why this is so important but… some runners inevitably overdo it. Unfortunately, overdrinking during endurance exercise has serious consequences.

What is hyponatremia?effects of drinking too much water

Hyponatremia (“natremia” comes from the Latin word for sodium, and means “sodium status”) describes a condition where an individual has very low levels of sodium in the blood. This may occur in prolonged endurance events such as a marathon, ultramarathon and long-distance triathlon, especially if the event occurs in hot and humid conditions.

Symptoms include vomiting, headache, bloating, swollen feet and hands, disorientation, and undue fatigue.

Fluid overload is the main cause of exercise-induced hyponatremia (EIH). Consuming excessive fluids, specifically large amounts of water, deplete the athlete’s sodium level leading to a serious condition requiring immediate medical attention.

Who Is At Risk?

As the length of a workout or race increases (>3-4 hours) so to does the risk of hyponatremia. For example, in a marathon those at greatest risk are middle or back of the pack athletes. Because slower athletes spend more time completing the distance they will consume more fluid than faster racers.  As the popularity of the marathon distance continues to increase there are more runners still on the road 5 or 6 hours after the race start. The risk is even greater for endurance athletes participating in ultramarathons or long-course triathlons.


How Do You Prevent Hyponatremia?

  1. Drink To Thirst

Since overdrinking is the root cause of hyponatremia, I recommend drinking to thirst in most situations. Don’t overthink it, if you are thirsty then drink. You can also use the sweat rate calculation (from a previous post) to serve as a general guide. Warmer conditions will require more fluid while you will need less in milder conditions.


  1. Consume beverages, foods or supplements that contain sodium

Know that if your training session or race is longer than 1.5-2 hours you will need to consume carbohydrates. A common way to get in these calories is to consume a sports drink, which will contain electrolytes. You may also include salty foods during exercise or in your pre-exercise meal.


However, if your training session goes beyond 3-4 hours and you are a ‘heavy sweater’ then you should consider supplementation. Fortunately, there are quite a few companies now that provide products with electrolytes like Endurolytes, Nuun, or Tailwind Nutrition.


Remember, if you do supplement with sodium it is VERY important to monitor your intake to ensure that you aren’t consuming excessive amounts.


  1. Develop a hydration plan that includes electrolytes.

Ultimately, you need to develop a hydration plan which includes the use of electrolytes. This could be from sports drinks, food consumed (like in an ultramarathon), or electrolyte supplementation.

For example, when I’m competing in a marathon or ironman triathlon I will take 2 Endurolytes during the final hours of each race just for insurance.

The longer your event the more important it is to have a hydration plan that you’ve tested in training!



Hyponatremia is a condition that can be prevented with education and a little planning. Be sure to share this information with other athletes who might find this helpful.

Now it’s your turn. What’ your hydration plan look like and does it include sodium supplementation? If so, how much—I’d love to know.


See ya next time–

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