Should I Drink Water While Running? The Real Science Behind Hydration During Runs

Ever finished a run feeling like your mouth is full of cotton, your legs are heavy, and your head is spinning? You might’ve skipped a drink before you headed out-or thought, “I’ll just wait till I’m thirsty.” That’s a mistake. Drinking water while running isn’t optional. It’s the difference between finishing strong and collapsing at mile three.

Why hydration matters more than you think

Your body is about 60% water. When you run, that water leaves your body through sweat. In Perth’s summer heat, you can lose up to 1 liter of fluid per hour. Even a 2% drop in body water starts hurting your performance. That’s not some vague fitness myth-it’s backed by the American College of Sports Medicine. At that point, your heart has to work harder. Your muscles fatigue faster. Your brain gets foggy.

Think of your body like a car engine. Run it without coolant, and it overheats. Same with you. Sweat isn’t just water-it’s salt, potassium, magnesium. Lose too much, and your muscles cramp. Your pace drops. You might even get dizzy.

When should you drink? Not just when you’re thirsty

Thirst is a late warning sign. By the time you feel it, you’re already dehydrated. Studies from the Journal of Athletic Training show runners who wait for thirst lose performance faster than those who sip regularly.

Here’s what works:

• Before you run: Drink 150-300ml of water 20-30 minutes before you head out. No chugging. Just enough to start hydrated.
• During your run: Sip 150-200ml every 15-20 minutes. Even on short runs under 45 minutes, this helps maintain steady performance.
• After you finish: Weigh yourself before and after. For every kilogram lost, drink 1.5 liters of water. That’s because you’re still sweating after you stop.

Try this: Next time you run, carry a small bottle or use a hydration belt. Take a sip every time you pass a lamp post or tree. It’s not about gulping-it’s about keeping your fluid levels steady.

What if you’re running for less than 45 minutes?

If you’re doing a quick 5K or a short tempo run in cool weather, you might not need to drink mid-run. But that doesn’t mean you can skip pre-run hydration. Most people start their runs already low on fluids-especially if they drank coffee or alcohol the night before.

Here’s a real example: A runner in Perth does a 30-minute morning jog. She skips water because she thinks it’s too short. She feels fine… until day three, when she gets a headache and cramps in her calves. Turns out, she’d been running on low fluid for days. Her body had adapted to being dehydrated-and it was paying the price.

Water vs. sports drinks: Which one do you actually need?

For runs under 60 minutes, plain water is fine. No need for fancy electrolyte drinks. They’re loaded with sugar and often unnecessary.

But if you’re running longer than an hour-especially in heat-you start losing sodium. That’s when you need electrolytes. A simple trick: Add a pinch of salt to your water. Or choose a low-sugar electrolyte tablet. Brands like Nuun or Liquid I.V. work well, but even a homemade mix of water, a dash of salt, and a splash of orange juice does the job.

Don’t fall for the hype. You don’t need a $5 sports drink for a 40-minute jog. But if you’re doing a 10K, half-marathon, or trail run in 30°C heat? Then yes-electrolytes matter.

Signs you’re drinking too much (yes, that’s a thing)

Drinking too much water while running can be dangerous. It’s rare, but it happens. Called hyponatremia, it’s when your blood sodium gets dangerously diluted. Symptoms: nausea, confusion, swollen hands, vomiting, and in extreme cases, seizures.

Who’s at risk? Slow runners who drink too much at every water station. Marathoners who chug at every mile. If you’re running slower than 9 minutes per kilometer and drinking 500ml every 15 minutes? You’re in danger zone.

Rule of thumb: Drink when you’re thirsty, not because everyone else is. If you’re not sweating much and your urine is clear, you’re probably overdoing it.

Practical tips for staying hydrated on the go

You don’t need fancy gear. But you do need a system.

• Handheld bottle: Good for 5K-15K runs. Lightweight, easy to grip.
• Hydration belt: Holds two bottles. Great for longer runs without stopping.
• Backpack hydration pack: For trail runs or long distances. Lets you carry more water and snacks.
• Water stations: If you’re in a race, plan your stops. Don’t grab a cup and chug-sip slowly.

Pro tip: Freeze your water bottle the night before. It stays cold longer and gives you a little extra cooling effect as it melts.

What about running in cold weather?

You don’t sweat as visibly in winter-but you’re still losing fluids. Cold air is dry. You lose water through your breath. And if you’re wearing layers, you might not even notice how much you’re sweating.

Runners in Perth’s winter often skip hydration because they don’t feel hot. Big mistake. One study in the British Journal of Sports Medicine found winter runners lost just as much fluid as summer runners-just slower. Drink the same way. Sip regularly. Don’t wait until you’re parched.

How to test your own hydration needs

Everyone’s different. Your sweat rate depends on your size, fitness, and genetics. Here’s how to find your personal number:

1. Run for 60 minutes at your normal pace.
2. Don’t drink during the run.
3. Weigh yourself naked before and after.
4. For every kilogram lost, you need 1.5 liters of fluid to rehydrate.

Example: You lose 0.8kg. That means you lost about 800ml of fluid. You should aim to drink around 600ml per hour during future runs to stay even.

Do this twice-once in summer, once in winter. You’ll see how your needs change with the season.

Final rule: Hydration isn’t about drinking more. It’s about drinking right.

You don’t need to guzzle water before every run. You don’t need to carry a gallon. You don’t need to chug at every water station.

You just need to be consistent. Sip before. Sip during. Sip after. Listen to your body. Track your sweat. Adjust for heat and distance.

Running is about rhythm. So is hydration. Make it part of your routine-not an afterthought.