The day I discovered that “more water” is not always the solution.
Kilometer 20 of a MTB route I had been looking forward to for months. Suddenly, the world began to wobble under my wheels. It wasn’t the technical terrain or normal race fatigue: something was very wrong.
My first instinct was that of any athlete: “I must be dehydrated”. So I did what I thought was right: I drank and drank from the jerrycan full of pure water. Each sip, instead of giving me strength, seemed to sink my body deeper into a strange sense of weakness.
The dizziness intensified, the nausea came on like an unstoppable wave, and my legs felt like jelly. I barely managed to pedal 3 more kilometers before admitting defeat. At the infirmary, the word that changed my perspective on hydration: hyponatremia.
Two days later, fully recovered but with a lesson burned into my heart, I decided that this experience had to be more than just an anecdote. If you’re reading this, you probably want to avoid going through the same thing.
Hyponatremia: when your body is screaming “stop drinking water now!”
Imagine your blood as a soup. Hyponatremia occurs when you dilute that soup so much that it loses all its flavor: the sodium concentration drops below 135 mEq/L. It’s like pouring too much water into a broth until it becomes tasteless and no longer nourishing.
Your body needs that “salty taste” in your blood for your cells to function properly. Without it, you start to experience anything from mild discomfort to really dangerous situations.
The numbers every athlete should know
If you were to get a blood test tomorrow, you’d want to see sodium numbers between 135 and 145 mEq/L. For those of us who sweat liters every workout, ideally you want to stay in the upper end of that range (136-145 mEq/L).
Think of it this way: if you’re going to “waste” sodium by sweating, it’s better to start with full reserves.
The silent culprit: why low sodium happens
Here comes the cruel irony of sport: the enemy is not always the lack of hydration, but the excess of incorrect hydration.
The most common scenario (and the one I experienced firsthand): You drink water as if it were the solution to all ills. Your body, which is already losing sodium through sweat, gets liters of pure water that further dilutes what little it has left. It’s like trying to fix an unpalatable soup by adding more water.
Other less obvious culprits: extreme sweating without adequate replenishment, gastrointestinal problems during competition, or simply genetics that cause you to lose more salt than normal.
Warning signs you should not ignore
Your body is pretty good at letting you know when something is wrong. In my case, the signs were escalating:
The first warnings (which I ignored like a champ):
- That nausea that I thought was “normal” from exertion
- A headache that I attributed to the sun
- Cramps that I interpreted as lack of training
- Fatigue that did not correspond to my actual effort
The “this is serious now” signs (which I luckily didn’t get to experience):
- Start to lose yourself mentally
- Seizures
- Loss of consciousness
If you feel any of the early symptoms during a race, do what I didn’t: stop and get help. Your personal best can wait, your health can’t.
A more common problem than you think in endurance sports
I am not alone in this. Exercise-associated hyponatremia (EAH) is like the unwanted guest at endurance events. In marathons like the Boston Marathon, up to 13% of participants have had to deal with it.
The tests you have on the horizon in 2025 and where you should be especially vigilant:
- San Fermín 2025 Half Marathon (June 21) – Pamplona’s heat is unforgiving
- Andorra Epic MTB 2025 (3-6 July) – Altitude and Sustained Effort
- Spanish School Cycling Championships (July 4-6, Albacete) – For the youngest, even more vulnerable
- Sierra Nevada Límite MTB (July 12) – Altitude and temperature: perfect combination for problems
- Transgrancanaria ( February 19-23) – Ultraresistance where every detail counts
In each of these tests, someone will be living what I lived. The difference is that you will already be prepared.
What to do when it is too late
If symptoms are mild: Stop drinking water as if it were medicine. Reduce fluid intake and look for something with salt. This is no time to be a hero.
If it gets serious: You need immediate medical attention. Professionals will use hypertonic saline intravenously. Sounds technical, but it’s basically putting the “salt” back into your blood soup in a controlled manner.
How to prevent what happened to me from happening to you
After my experience, I completely changed my hydration strategy:
During the competition:
- Forget pure water: If it is going to be in your water bottle for more than an hour, make sure it has electrolytes.
- Listen to your thirst: Your body is smarter than any rigid hydration plan.
- Eat salty without complexes: Those pretzels they sell at the refreshment posts are not by chance.
Smart preparation: To complement this strategy, check out our guide on what to eat before a trail running competition where you’ll find more tips on nutritional balance.
Also consider optimizing your recovery with our 2025 muscle recoverer comparison and, if you’re looking to maximize your endurance performance, check out the best creatine comparison.
What I really learned that day
It wasn’t just a lesson in electrolytes. It was a reminder that in sport, as in life, sometimes “more” is not better. Sometimes the answer is not in quantity, but in balance.
Now, every time I see someone drinking only water in a long competition, I reach out and share my story. Because if my experience can keep someone else from going through those two days of recovery and that feeling of frustration, it will have been worth it.
Questions I would have liked to ask earlier
Is it really so bad to hydrate with water alone? For short workouts, no problem. But for anything longer than an hour in the sun, you’re playing Russian roulette with your electrolyte balance.
How do I know if I need a sodium analysis? If you experience regular symptoms during long workouts, it is worth a check-up. A simple blood test can give you the answer.
How do I distinguish between hyponatremia and actual dehydration? Hyponatremia makes you confused and nauseous; dehydration gives you intense thirst and obvious dryness. In my case, I wasn’t thirsty at all: that was the first clue.
What do I drink during a race? Isotonic drinks that replenish sodium, potassium and magnesium. Read labels: they are not all the same. Look for those with at least 200-400mg of sodium per liter.
