What Happens to Your Body When You Don’t Hydrate Right? (And How to Fix It)
You’ve heard it a million times: stay hydrated. But most runners still get it wrong.
And the scariest part?
You often don’t even realise you’re dehydrated until your performance tanks.
So let’s break it down. What’s actually happening in your body when you’re not hydrated enough? What are the hidden mistakes runners make? And how can you fix it before it wrecks your run?
Why Hydration Matters More Than You Think
Water isn’t just for cooling down on a hot day. It’s critical for almost every process in your body.
We’re talking temperature regulation, oxygen delivery, nutrient transport, and waste removal. And when you run, especially in the heat or over long distances, your body bleeds fluid through sweat.
And with it, electrolytes that keep your nerves firing and muscles working.
When hydration drops, your performance nosedives.
The Common Mistakes Most Runners Make
You might think you're doing fine, but here are the usual culprits that sneak up on even smart runners:
Starting your run already dehydrated. Skipping morning fluids or not drinking enough during the day.
Drinking only water. You sweat out electrolytes. If you don’t replace them, you risk imbalance.
Relying on thirst alone. By the time you feel thirsty, it’s often too late. You're already behind.
Ignoring the weather. Heat and humidity double your fluid loss. You need to adjust intake accordingly.
Guessing instead of tracking. Without a plan, it’s easy to under-hydrate or over-hydrate.
The Risks of Dehydration
Even mild dehydration messes with your performance and recovery. Here’s what it can lead to:
Slower pace and increased effort
Brain fog and poor decision-making
Muscle cramps and tightness
Headaches, fatigue, dizziness
Heat exhaustion or even heat stroke
What the Research Says
You don’t have to take our word for it:
One study in the Journal of the International Society of Sports Nutrition found that just 2% body weight loss from dehydration impaired endurance performance significantly.
Another in Medicine and Science in Sports and Exercise showed runners dehydrated by 3% or more saw sharp performance declines compared to those who stayed hydrated.
In other words, you could be holding yourself back without even knowing it.
How to Stay Hydrated the Right Way
This isn’t about overloading on water or sipping nonstop. Here’s what actually works:
1. Drink Regularly
Aim for 8 to 10 glasses a day minimum. More if you’re training or sweating heavily.
2. Check Your Pee
Light yellow = good. Dark yellow or infrequent urination = probably need more fluids.
3. Don’t Ditch Electrolytes
Use sports drinks, electrolyte tablets, or even coconut water. Especially during longer sessions.
4. Eat Hydrating Foods
Watermelon, cucumbers, oranges. They help boost fluid intake.
5. Adjust for Heat
Hot day? You need more water and more salt. It’s that simple.
Pre, During, and Post-Run Hydration Game Plan
Before: Sip water or a sports drink 30 to 60 minutes pre-run.
During: Hydrate every 10 to 15 minutes, especially if running over an hour.
After: Replenish lost fluids and salts within 30 minutes of finishing.
Conclusion
Hydration isn’t just a summer thing. It’s an every run thing.
When you hydrate smart, you run smoother, feel better, and bounce back faster. And you avoid that wall that sneaks up when you’re running on empty.
So let’s end with a little self-check:
Do you actually hydrate well enough to fuel your performance?
Reply yes or no. Let’s find out what needs to change.
Yours in running and life,
Daniel Lucchini
References:
Journal of the International Society of Sports Nutrition, "Effects of dehydration on exercise performance" (2018)
Medicine and Science in Sports and Exercise, "Dehydration and athletic performance" (2015)