How Many Carbs Per Hour for a Marathon (and Why It Takes Practice)

The number you need first: 60–90 grams of carbohydrate per hour during a marathon.

That range is where current sports-nutrition consensus sits for most recreational marathoners. Elite runners push further — some are documented taking in 90–120 g/hr — but they've spent months conditioning their gut to absorb that volume without revolt. Don't start there.

For a half-marathon under 90 minutes, you can get away with 30–60 g/hr. The race is short enough that your glycogen stores, topped up before the gun, can carry most of the load.

Why the blend matters above 60 g/hr

Your gut uses different transporter proteins to move glucose and fructose into the bloodstream. Glucose transporters saturate at roughly 60 g/hr. If every gram of carb you're taking in is glucose — maltodextrin, most plain gels — you've hit a ceiling. Add fructose (in roughly a 2:1 glucose-to-fructose ratio) and you open a second lane. That's why anything above 60 g/hr needs to come from a blend, not a single-source product. Check the label.

The real unlock: gut training

Here's the part most runners skip. GI tolerance on race day is almost entirely a product of what you practiced during your build. Your intestines adapt to processing carbs under running stress, but only if you give them the stimulus repeatedly.

The practical protocol: start your early long runs at 30–40 g/hr. Every two to three weeks, add 10–15 g/hr. By the time you hit peak training, you're rehearsing race-day intake — same products, same timing, same volumes. Your gut learns. Skipping this and then downing four gels in the back half of the race is a recipe for a porta-potty detour.

Bottom line for your training

Pick a glucose-fructose gel or chew, set a timer for every 30–45 minutes, and start conservative. Ramp the dose across your build just like you ramp mileage. Fueling is a skill, and your long runs are the practice field.