During running, drink 150–250 ml every 15–20 minutes. For a 60-minute run, plan for 600–1,000 ml total. Before running, drink 400–600 ml in the 2–4 hours prior.
Running creates one of the highest sweat rates of any common exercise. Depending on your pace, body weight, and the weather, you can lose 500–2,000+ ml per hour. Unlike gym workouts where water is always within reach, runners must plan ahead and carry fluids or know their route's water sources.
Both under-hydrating and overhydrating during running carry real risks — from performance decline to the rare but dangerous exercise-associated hyponatremia (EAH). Getting it right requires understanding your individual sweat rate.
Your personal sweat rate is the gold standard for planning hydration. To measure it:
Most runners lose 400–1,200 ml per hour at moderate pace. Heavier runners and hot-weather runs skew higher. Test in different conditions because your rate changes significantly with temperature.
Heat multiplies everything. A runner who loses 600 ml/hour at 15°C might lose 1,200 ml/hour at 30°C. If you're running in summer or tropical conditions:
Slower runners and those doing long events face a counterintuitive risk: drinking too much. Exercise-associated hyponatremia occurs when excessive fluid intake dilutes blood sodium. Symptoms include nausea, headache, confusion, and in severe cases, seizures.
Prevention is simple: don't drink more than your sweat rate dictates, and don't force fluid beyond what you lose. Following a "drink to thirst" approach is safer than drinking on a rigid schedule for most recreational runners.
For runs under 45 minutes in moderate weather, pre-hydrating may be sufficient. For longer runs, carry water using a handheld bottle, vest, or plan routes past water fountains.
Hydrate normally in the days before. Morning of: 500 ml 2–3 hours prior. During: 150–200 ml every 15–20 minutes. After: 150% of weight lost. Practice your hydration strategy during training runs.