How many carbs per hour do you need during exercise?

Carbs per hour by session length

Asker Jeukendrup’s 2014 review in Sports Medicine is the reference we use for these figures ^[3]. It sets carbohydrate targets by duration, not by body weight. Jeukendrup found no reason to scale intake to body weight or training status, because the limiting factor is most likely how fast your gut absorbs carbohydrate, and that doesn’t depend much on body size ^[3].

Session length	Carbohydrate guideline [3]
Under about 30 minutes	None needed
About 30 to 75 minutes	Small amounts, or a mouth rinse
1 to 2 hours	Up to 30 g/h
2 to 3 hours	Up to 60 g/h
More than 2.5 hours	Up to 90 g/h, glucose plus fructose

These are upper figures for well-trained athletes. Jeukendrup says less experienced athletes may need to adjust them down ^[3]. Treat them as a ceiling to work toward, not a number to force down on your first long run.

Why the short end is “almost nothing”

In efforts of around an hour, carbohydrate can still help performance, but Jeukendrup found even rinsing a sports drink around your mouth and spitting it out produced a benefit in some studies ^[3]. Jeukendrup points to brain regions that respond to carbohydrate in the mouth as a likely explanation, since it isn’t fuel reaching the muscles. So for a hard one-hour race, a few sips of sports drink is plenty. For a steady one-hour workout, water is fine. Our sports drink vs water guide covers that choice.

Why the long end needs two kinds of sugar

Your gut absorbs different sugars through different routes. Glucose uses one route, and it fills up. Jeukendrup’s review says a single carbohydrate source can be burned at up to about 60 g/h ^[3]. That’s why the 2 to 3 hour guideline stops there.

Adding fructose opens a second route. Mixed glucose and fructose let athletes absorb and burn more carbohydrate per hour than glucose alone, which is how the highest guideline of up to 90 g/h becomes possible ^[3]. The ACSM position stand on fluid replacement makes the same point: a mixture of sugars delivers carbohydrate at the highest rates ^[6].

On a label, look for more than one sugar in the ingredients: sucrose (which is half glucose, half fructose), or dextrose or maltodextrin combined with fructose. Our sugar in sports drinks guide explains the label terms.

Train your gut first

High hourly intakes can upset your stomach if you haven’t practiced them. Jeukendrup recommends practicing your race fueling in training, including some sessions at a relatively high carbohydrate intake ^[3]. Start below your target on long training days and build up over weeks. Race day is the wrong place to try it for the first time.

Getting your carbs from drinks

Drinks are the easiest way to take in carbohydrate, since you’re drinking anyway. But fluid and fuel pull against each other.

Jeukendrup notes that carbohydrate intake has to fit a fluid plan, and that highly concentrated carbohydrate drinks can reduce fluid absorption ^[3]. The ACSM says a drink meant to supply both fluid and carbohydrate should stay at or below about 8% carbohydrate ^[6]. At that strength, hitting the higher hourly targets from a classic sports drink alone takes a lot of fluid, often more than thirst calls for.

Athletes solve this in two ways:

• Concentrated drink mixes: High-carb mixes pack more carbohydrate into each bottle. For example, per serving as directed: Skratch High-Carb Hydration has 50 g, Tailwind Endurance Fuel has 25 g, and Maurten Drink Mix 320 has 80 g. Concentrated mixes can land in the hypertonic range, so check each product page, and keep plain water on the side. See isotonic, hypotonic and hypertonic drinks.
• Drink plus food: A standard sports drink or electrolyte mix for fluid and sodium, plus gels, chews or real food for the rest of the carbohydrate. This splits fluid and fuel, so you can drink to thirst and eat to your carb target.

For comparison, Gatorade Thirst Quencher has 59 g of carbohydrate per liter and Gatorade Endurance Formula has 59 g.

Putting a number on your session

1. Set the target: Pick the band for your session length from the table.
2. Set your fluid: Use the sweat rate calculator to see how much you lose. Drink to thirst, and don’t plan to drink more than you sweat.
3. See what your drink gives you: The hydration calculator takes your session length, intensity and sweat rate, returns carbohydrate, sodium and fluid ranges per hour, and shows how many servings of each drink it would take.
4. Fill the gap with food: Whatever the drink doesn’t cover, cover with gels, chews or snacks.

For long races, our best electrolytes for endurance rankings sort drinks by how well they cover sodium and carbohydrate together. Runners can start with the electrolyte drink for runners list.

Don’t drink extra to hit a carb number

If your carb plan depends on drinking a lot, change the plan, not your drinking. Drinking beyond thirst is the main cause of exercise-associated hyponatremia, a dangerous drop in blood sodium ^[5]. Get the extra carbohydrate from food or a more concentrated mix instead.