Starting your run dehydrated or over-hydrated is a recipe for disaster. Too little water and you’ll feel sluggish, while too much can leave you bloated or needing frequent bathroom breaks.

Tips for Pre-Run Hydration:

• A solid base: you need 2-3 litres of water a day to be normally hydrated before accounting for any exercise.  If you're not achieving this then it should be your focus.

• Start early: Hydrate well in the 24 hours before a long run or race—sip water consistently, don’t just chug a bottle an hour before.

• Aim for pale yellow urine: A good sign that you’re hydrated, but not over-hydrated.

• Consider electrolytes: If you’ll be running over 60-90 minutes, adding electrolytes to your pre-run drink can help maintain fluid balance and prevent cramps.

💡 Tip: About 1-2 hours before your run, have a large glass of water and then sip more as needed—don’t glup down lots of water just before you head out to run.  Taking on lots of water can overload the kidneys, leading to fatigue and you will simply urinate the excess out rather than absorb it into your body.

Hydrating During Long Runs & Races: Stay Smart

During long runs and marathon training, hydration and electrolytes are critical for sustaining energy and preventing issues like cramps and dizziness.

How to Hydrate on the Run:

• Drink to thirst but before you are thirsty: Avoid forced drinking schedules—listen to your body and take regular sips.  If you wait till you are thirsty, you've waited too long!

• Use aid stations wisely: At races, aid stations are great for hydration, but don’t gulp water too fast—you’ll risk choking or bloating. Instead, pinch the cup into a spout and sip slowly while moving or even consider walking briefly to drink in a controlled way.

• Take electrolytes: For runs longer than an hour, include electrolyte drinks or salt tabs. This replaces sodium and other minerals lost in sweat.

• Practice during training: Use your long runs to practice drinking on the move, so you know what works for you on race day.

💡 Tip: Plan routes with water refill points or carry hydration packs if you’re running long distances in training.

💡 Tip: Some gels require you to drink water with them.  Check the packaging of your chosen gels to check - it will say on them.

Post-Run Hydration: Replenish and Recover

After a tough long run or race, rehydrating properly is essential for recovery.

Post-Run Hydration Tips:

• Drink to thirst initially: Start with water, then switch to an electrolyte drink to replace salts.

• Don’t overdo it: Too much water without electrolytes can dilute your body’s sodium levels.

• Monitor urine color: Pale yellow is a good goal post-run, but don’t aim for clear—clear urine may signal over-hydration.

• Refuel as well: Combine hydration with a recovery meal including carbs and protein to help muscle repair (see my blog on fuelling).

Want to be more scientific?

If you want to be precise, then it is recommended to weight yourself before and after running.  The weight loss indicates your fluid loss.  Take that amount in grams and multiply it by 1.2 to 1.5.  This equals the amount of water in millilitres (ml) you need to take on - here a couple of examples: