How Many Carbs Per Hour for Cycling and Running?

Carbohydrate intake during endurance exercise is the most well-studied variable in sports nutrition. The research answer is clear. Most athletes are either underfueling or using the wrong carbohydrate source to fuel at higher rates.

How many carbs per hour?

The carbohydrate intake target depends on event duration and the carbohydrate source. For a single sugar (glucose, maltodextrin only, or sucrose), the ceiling is 60g per hour. For a 2:1 maltodextrin-to-fructose blend, the ceiling is 90g per hour. No known mechanism allows more than 90g per hour to be absorbed.

Event duration	Intensity	Carb target per hour
Under 1 hour	Any	0 to 30g (optional)
1 to 2 hours	Moderate	30 to 60g
1 to 2 hours	Race intensity	60g
2 to 3 hours	Race intensity	60 to 90g
Over 3 hours	Race intensity	90g (dual-transport required)
Ultra events (over 6 hours)	Submaximal	60 to 90g (gut tolerance often limits this)

Why 60g is the single-sugar ceiling

The small intestine uses the SGLT1 transporter to absorb glucose and maltodextrin. SGLT1 saturates at approximately 60g of glucose equivalents per hour. Beyond that rate, unabsorbed carbohydrate remains in the gut, draws water in by osmosis, and causes bloating, cramping, and diarrhea.

This ceiling applies regardless of how much carbohydrate you consume. Eating a gel every 15 minutes above the 60g limit does not produce more energy: it produces GI distress.

Why fructose unlocks 90g per hour

Fructose uses a different transporter, GLUT5, which is independent of SGLT1 and can absorb 30 to 36g per hour. A 2:1 blend of maltodextrin to fructose saturates both SGLT1 and GLUT5 simultaneously, raising the functional ceiling to 90g per hour.

This is the mechanism behind Maurten, SIS Beta Fuel, and every high-carb race formula that advertises above 60g/h absorption. It is not marketing. The dual-transporter mechanism has been replicated in multiple peer-reviewed studies since 2004.

How to train your gut for 90g per hour

Your gut absorbs more carbohydrate when trained to do so. Attempting 90g per hour on race day without prior gut training is the most common cause of GI failure in endurance racing.

A 3 to 4 week gut-training protocol:

• Week 1: 60g per hour during all rides or runs over 90 minutes.
• Week 2: 70g per hour on long sessions, 60g on shorter ones.
• Week 3: 80g per hour on long sessions.
• Week 4 (race week): Full 90g per hour in at least one race-simulation workout.

Practice with the exact products or DIY recipe you plan to use on race day. Do not train on one product and race on another.

Practical carbohydrate sources and their carb content

Source	Serving size	Carbs per serving
Standard energy gel (SIS, GU)	32g packet	22g
Maurten Gel 100	40g packet	25g
Banana (medium)	120g	27g
Medjool date	24g (1 date)	18g
Rice cake (homemade, 2-inch)	50g	22g
DIY maltodextrin-fructose drink	500mL	67g (2:1 blend)

At 90g/h from gels alone, you would need 4 standard gels per hour, which is expensive and impractical. A DIY carbohydrate drink handles the baseline (60 to 70g/h) and gels or solids supplement it.

Use the carbs per hour calculator to get your exact in-race target from your event duration, intensity, and gut training level, then use the DIY sports drink calculator to build a 2:1 blend matched to that hourly target and combine with solid food for longer events.

For a ranked comparison of commercial gels by carb ratio, see best marathon gels.

Frequently asked questions

Can you train your gut to absorb more carbs?

Yes. The gut adapts to higher carbohydrate intake over 3 to 4 weeks of consistent practice. The SGLT1 transporter upregulates with repeated high-carb exposure, which means more glucose can be absorbed per hour. Athletes who attempt 90g per hour on race day without prior gut training frequently experience cramping, bloating, and diarrhea. The protocol is to progressively increase carbohydrate intake during long training sessions over several weeks using the exact products and recipe you plan to use in the race.

What happens if you eat too many carbs during a race?

Consuming more carbohydrate than your gut can absorb leaves undigested sugars in the small intestine. These draw water in by osmosis, causing bloating, cramping, sloshing, and diarrhea. Above the 60g per hour single-sugar ceiling, or above 90g per hour even with a dual-transport blend, excess carbohydrate produces GI distress without delivering more energy to working muscles. This is the most common cause of GI failure in endurance racing and is almost always a result of exceeding the absorption ceiling without adequate gut training.

How many carbs can the body absorb in an hour?

The maximum is approximately 90g of carbohydrate per hour using a 2:1 maltodextrin-to-fructose blend that saturates both the SGLT1 and GLUT5 intestinal transporters simultaneously. With a single sugar source (glucose, maltodextrin only, or sucrose alone), the ceiling is about 60g per hour because only the SGLT1 transporter is available. No known physiological mechanism allows more than 90g per hour to be absorbed, regardless of how much carbohydrate is consumed or how well trained the gut is.

Is 90 grams of carbs per hour too much?

For events under 2.5 hours, 90g per hour is unnecessary and more than most athletes need or can tolerate without prior gut training. For events over 3 hours at race intensity, 90g per hour is the evidence-based target when using a dual-transport blend and when the gut has been trained to handle it over several weeks. At submaximal intensity in ultra events over 6 hours, gut tolerance often limits practical intake to 60 to 75g per hour even in trained athletes, making 90g/h more of a ceiling than a target for those conditions.