It is important to keep hydrated when running a marathon but did you know that too much water can be a bad thing?
A good rule of thumb is to drink about one cup of fluid every 20 minutes during a marathon, anything more than that could be dangerous and could cause hyponatremia — when you have low amounts of sodium in your body. It can be fatal if not treated immediately. To prevent it, be sure to drink sports drinks during training and, as long as you don't have high blood pressure, increase your salt intake a few days before the race.
For symptoms of hyponatremia just read more.
Symptoms of hyponatremia include:
- Vomiting.
- Loss of appetite.
- Headache.
- Restlessness/fatigue.
- Abnormal mental status (hallucinations, confusion, change in personality, etc.)
- Muscle weakness.
- Convulsions.
Fit's Tip: If you experience any symptoms, you should see your doctor.

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Marlies Dekkers
I only try and drink half my water bottle when i am at the gym for an hour.
1Oh wow I had no idea, good to know...
2I try to eat something a bit salty the day before a long run so I don't get hyponatremia. I could see how drinking too much water could happen though. It's very easy to drink too much when you're working out.
3Didn't know this either, thanks for the tip! Sometimes I push myself too hard and then I end up drinking tons of water because I'm so tired.
4except on the hottest days, i don't even take a water bottle when i go running. i just drink a lot when i get back. i don't really like the feeling of water sloshing around in my stomach while i'm moving, so i doubt i would ever be in the situation where i'd end up drinking too much water during a run.
5Yah...during Bikram Yoga they would tell us to not go crazy with water because of this same reason. Electrolytes are KEY.
6I think I accidentally drank too much last night. I realized I was about 40 mins in without a sip of water and I was so hot and thirsty that I downed half my bottle right away. Then I ended up with a cramp and wasn't able to finish my workout as efficiently as I'd been going pre-water.
7You have to drink a lot of water to cause cases of hyponatremia. Usually in races longer than 3 hours. The only cases I have seen have been in Ironman distance races and Half Iron distance races. For a little more information and some helpful tips read http://www.rice.edu/~jenky/sports/salt.html This is a great article and includes the sodium listings of many popular items. For instance for you to get your lost sodium back from gatorade you would have to driink over 2 liters an hour. Not very practical. I personally use salt tabs when I am on long bike rides or runs. Just remember to drink.
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