How much water should I drink while running?
Drink 400-800 ml of water per hour of running, sipping every 15-20 minutes. For runs under 60 minutes, water before and after is usually enough. For runs over 90 minutes, add electrolytes. Thirst is a reasonable guide — drink when thirsty, don't force fluids on schedule.
Hydration for running isn't as complicated as marketing makes it seem. For runs under 60 minutes at moderate temperatures, you generally don't need to drink during the run — just hydrate well before and after. For runs of 60-90 minutes, 200-400 ml during the run is plenty for most people. For runs over 90 minutes or in heat, aim for 400-800 ml per hour, ideally with electrolytes (sodium 300-500 mg per 500 ml) to replace what you sweat out. The old advice of drinking on a schedule regardless of thirst led to hyponatremia (dangerously low sodium) cases in slower marathoners. Current sports medicine guidance: drink to thirst during activity, which for most runners means 150-300 ml every 15-20 minutes during long runs. Sweat rate varies hugely — weigh yourself before and after a 1-hour run to calculate yours (1 kg weight loss = ~1 liter fluid loss). Runners in hot climates like India can lose 1.5-2 liters per hour, so they need more. Signs of dehydration: dark urine, fatigue disproportionate to effort, headache, cramping. Signs of overhydration: clear urine, nausea, confusion, swollen fingers. Pre-run: 400-600 ml 1-2 hours before. Post-run: 500 ml per 0.5 kg of weight lost, within 2 hours.