Ultrarunning: The Risk of Drinking Too Much During an Ultra

May 1, 2012

This article is part of Endurance Planet’s ultrarunning article series. If you have questions, comments or feedback about “The Risk of Drinking Too Much During an Ultra”, please leave it below in the comments section…

There’s a lot of advice and guidelines for handling dehydration. Most of the sports drinks available out there are often marketed as solutions to thirst. Running all those miles in an ultramarathon can certainly drain you of much needed fluids and you probably know about the risks that entails. What may not have been emphasized enough however is the danger of swinging to the opposite direction – drinking too much or over-hydrating. You wouldn’t naturally think that you could take in too much water while running and sweating under all that heat or humidity. But it’s a real risk that can result in what is known as hyponatremia.

Too much fluids and not enough salt

That is basically the internal situation in your body when you have hyponatremia. Sodium is an important substance that keeps your muscles and nerves functioning properly. Most of it is found in the blood or other body fluids outside your cells. There is a normal or balanced state between the amounts of sodium in relation to the fluids in your body. When sodium in the blood dips below the minimum range, most likely lost through sweating, fluids move into the cells to restore the balance. Most cells could accommodate this swelling except for the brain cells which are restricted by the skull bones. This is why majority of the symptoms of hyponatremia are neurological.

Symptoms and indicators

The condition is sometimes called water intoxication and an ultrarunner suffering it will be exhibiting an abnormal mental state. Early on there’s going to be nausea, headache, and vomiting. Then as the condition grows worse there will be confusion, hallucinations, loss of consciousness, and the very dangerous chance of slipping into a coma. Weight gain is another sign that doctors at an ultramarathon’s aid stations look for. When a runner’s weight is up that usually means he’s been taking in a lot of fluids and may possibly not be eliminating enough of the excess.

Balancing act

The complicated aspect about this condition is that there isn’t really any hard and fast rule that defines how much weight gain or fluid intake is excessive or dangerous. Drinking a lot of water by itself is not a bad thing. It only becomes dangerous when it isn’t balanced with a proportional intake of salt. Another factor that comes into play is when the rate of sweating is low such as what usually happens to those going at it a very slow pace. Then there is also the possible secretion of what is called anti-diuretic hormones (ADH), a physiological reaction to all that stress the body is being put through running an ultra. Diuretics are substances that make you urinate more like coffee so you can easily see how ADH can increase the risks of hyponatremia.

In the end proper management of fluid and salt intake and elimination is a balancing act that is different for every runner. The important thing to remember is to be conscious and careful about how you refuel and if the food or drinks you’re taking have enough sodium. Watch out for any of the symptoms and take advantage of any medical services being offered at the aid stations, even if it’s just to monitor your weight. There’s nothing wrong with slowing down or cooling off for a short while if you start feeling bad. If you ignore the early signs, you might have to face a bigger problem later on down the trail.


Do you have questions about hyponatremia, or what you’ve read so far? Do you have any ultrarunning pointers of your own to add? Please leave your feedback, comments and questions below, and we promise we’ll respond.

One Comment

  • Samantha says:

    Fellow runners always complain n hate to need to use the bathroom while running. I tell them it’s s good sign your hydrated and your pipes are working! It’s that true? In Ultra Distance it’s important you continue to urinate all day but how often? When is it too much fluid- causing leaching of salts thru excess urination and when is it normal flow? How often should we go during an ultra? Thanks!

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