Good running hydration means starting with normal fluid balance, drinking to thirst on the run, and replacing water and sodium afterward. Euhydration means your body holds a normal amount of water, neither dehydrated nor overfilled. Sweat rate, drink volume, and sodium needs change with pace, heat, and run length. A simple plan covers before, during, and after running.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What to drink before a run
- How much to drink while running
- Do you need water or electrolytes?
- How to find your sweat rate
- How to rehydrate after running
What to drink before a run
The American College of Sports Medicine advises about 500 mL fluid 2-4 hours before exercise, plus a salty meal or snack to hold water and start euhydrated, as detailed in its fluid-replacement position stand. That timing gives kidneys time to process extra fluid.
A practical start is water with breakfast or a salty snack. Runners with an early start can drink on waking, then eat toast, oatmeal, broth, or salted nuts. Pale yellow urine and steady energy often signal a good start.
How much to drink while running
The American College of Sports Medicine, summarized in a BMJ review, advises drinking to thirst at roughly 400-800 mL per hour and keeping loss under 2% of body mass, as explained in the BMJ review. Larger deficits can impair thinking and aerobic performance, especially in heat. Do not try to replace every drop during the run.
The U.S. CDC warns against gaining weight while exercising and against exceeding about 800 mL per hour. Overdrinking plain water can dilute blood sodium and cause exercise-associated hyponatremia, with seizures or death.
Do you need water or electrolytes?
The National Athletic Trainers' Association states water alone suffices for runs under about 60-90 minutes, while longer runs or heat call for a sodium-containing sports drink, according to its fluid-replacement statement. Sodium helps replace sweat electrolytes and sustain plasma volume.
For exercise over 2 hours, the American College of Sports Medicine evidence supports about 300-600 mg sodium per hour from drinks or food. That approach lowers dehydration and hyponatremia risk. Salty sweaters, heavy sweaters, and hot-weather runners should favor the higher end.
How to find your sweat rate
Dartmouth Sports, using National Athletic Trainers' Association guidance, gives sweat rate as pre-weight minus post-weight plus fluid drunk minus urine, divided by hours, as shown on its hydration worksheet. One kilogram of loss equals about 1 liter of sweat.
Typical rates run from 0.5 to over 2.5 liters per hour. Weigh nude before and after a one-hour run, track bottles drunk, and skip bathroom breaks when possible. Use the result to set hourly drink targets for similar weather and effort.
How to rehydrate after running
The Gatorade Sports Science Institute summary of ACSM guidance advises drinking about 150% of mass lost within hours, or about 1.5 liters per kg lost, with sodium and food. Extra volume offsets ongoing urine losses. Use these steps after long or sweaty runs:.
- Weigh when practical and drink gradually over several hours.
- Eat a salty meal or snack with water or sports drink.
- Avoid alcohol alone as recovery fluid because it adds urine loss.