Take into account the weather conditions before and during your planned run: If you’re likely to go through very hot weather before a long run, adapt your strategy to hydrating and replenishing with electrolytes before you head out, so you’re not starting out dehydrated
Be aware of your sweat rate and sodium loss and plan to take in electrolytes as well as water during a long session;
Account for exercise effort levels: you’ll sweat more during high-intensity shorter sessions, but you may not need to rehydrate for those. If you start hydrated, anywhere under 90 minutes will not require you to re-hydrate during the session. However, beyond that, make sure you recover your fluid intake per hour in accordance with your prepared hydration plan;
Stay flexible and attuned to your body’s signals: Feelings such as bloated, full, liquid sloshing in your stomach, needing to pee and struggling to force drinks down – mean you’re drinking too much; A dry mouth, feeling thirsty or light-headed, lethargic, and seeing a high heart rate reading compared to your pace – are all signs of drinking too little.