Hydration and Salt: How Much During Endurance Sports?
TL;DR — Drink about 400 to 800 milliliters per hour during endurance sports, more when it's hot. For efforts longer than an hour, add 300 to 700 milligrams of sodium per hour, more if you sweat heavily or it's hot. Sweat loss varies greatly per person, so these are guidelines. Too much water without salt is dangerous and can make your sodium dangerously low. Drinking to thirst works well for most people. My fuel plan tool outlines your fluid and salt per hour.
Carbohydrates get all the attention in fueling, but fluid and salt are just as crucial for staying healthy during prolonged exercise. Drinking too little impairs performance, while drinking too much without salt is downright dangerous. In the complete guide to fueling for cycling, hydration is part of the bigger picture. Here, I’ll give you honest guidelines for water and sodium per hour, without the exaggerated salt stories some brands sell.
How much fluid per hour
A useful rule of thumb is around 400 to 800 milliliters per hour. In cool weather and during a low-intensity effort, you'll be at the lower end, while in heat and high intensity, you'll be at the upper end. More important than an exact number is realizing that your sweat loss varies enormously. One athlete might lose half a liter per hour, another more than two liters. That's why drinking to thirst is a safe and sensible guideline for most athletes, especially if you have no idea of your own sweat rate.
When salt becomes necessary
For efforts up to an hour, you usually don't need extra sodium. You do lose salt through your sweat, but not enough to become a problem in that timeframe. If the effort lasts longer than an hour, sodium comes into play. A guideline is 300 to 700 milligrams per hour, and you'll go higher if it's hot or if you're a heavy sweater. If you often see white salt marks on your shirt or cap after exercising, you lose an above-average amount of salt and should be at the upper end of that range.
Why more salt isn't always better
This is where marketing often goes wild. You don't need extreme salt intake to perform. The real risk during prolonged exercise isn't too little salt, but too much water in proportion to your salt. If you drink liter after liter of water without sodium, you dilute the salt in your blood. This is called hyponatremia, and in severe cases, it can be life-threatening. The solution isn't to pile on more salt, but to keep salt and water in proportion. A sports drink with some sodium or an electrolyte tablet during prolonged exercise does the job perfectly.
Fluid, salt, and your carbohydrates together
The great thing is that you often manage these three at once. A good sports drink simultaneously provides fluid, some of your sodium, and some of your carbohydrates. If you drink 500 to 800 milliliters of sports drink per hour, you cover your fluid, a good portion of your salt, and 30 to 60 grams of carbs all at once. You can add 1 to 2 fruit performance bars per hour for the rest of your carbohydrates. For very long or hot efforts, supplement your salt with a separate electrolyte tablet. This way, you build a complete plan without overloading your stomach. How to practically distribute this is covered in my article about bar versus gel per moment.
| Situation | Fluid per hour | Sodium per hour |
|---|---|---|
| Up to 1 hour | 400 to 600 ml | usually not needed |
| 1 hour plus, moderate | 500 to 700 ml | 300 to 500 mg |
| Long and hot, heavy sweater | 700 to 800 ml | 500 to 700 mg |
Honest about your sweat, honest about your plan
Hydration isn't an exact science; it's about adjusting to your body and the conditions. Know the guidelines, drink to thirst, keep salt and water in proportion, and don't overdo the salt. My fuel plan tool asks about your sweat profile and the weather, and neatly lists your fluid and sodium per hour. No gel. No brick. Fuel during exercise. Fuel your flight.
The science
Guidelines for fluid and sodium intake during exercise are based on the American College of Sports Medicine position stand (Sawka et al. 2007), which recommends 0.4 to 0.8 liters of fluid per hour and sodium for efforts longer than an hour. A recent review on sodium intake for athletes (2025) confirms that the ratio of salt to water is more important than high salt intake itself.
Sources
Sawka MN et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc 2007. doi:10.1249/mss.0b013e31802ca597
McCubbin AJ et al. Sodium intake for athletes before, during and after exercise: review and recommendations. Performance Nutrition 2025. doi:10.1186/s44410-025-00011-9
Frequently Asked Questions
How much should I drink during exercise?
Approximately 400 to 800 milliliters per hour, depending on the heat and how much you sweat. Drinking to thirst is a safe guideline for most athletes.
How much salt do I need during endurance sports?
For efforts longer than an hour, about 300 to 700 milligrams of sodium per hour, more in heat or if you sweat heavily.
Can I drink too much water during exercise?
Yes. Too much water without salt dilutes the sodium in your blood, which is called hyponatremia and can be dangerous. Keep salt and water in proportion.
How do I know if I lose a lot of salt?
If you often see white salt marks on your shirt or cap after exercising, you are a heavy sweater and should be at the upper end of the sodium range.
Do I get enough salt from my sports drink?
Often yes, for moderate exercise. For long or hot efforts, supplement with an electrolyte tablet.
