Most marathon runners should aim for 60 to 90 grams of carbohydrates per hour during the race. The exact target depends on your finish time: if you’re running under three hours, 60 grams per hour is the standard recommendation, while runners on course for three hours or longer benefit from pushing toward 90 grams per hour. Some elite and well-trained athletes go even higher, up to 120 grams per hour, but that requires specific preparation and the right fuel mix.
The Standard Ranges by Finish Time
The American College of Sports Medicine recommends 60 grams of carbohydrates per hour for the first 2.5 hours of exercise, then up to 90 grams per hour beyond that. This lines up with how long you’ll actually be running. A sub-3:00 marathoner may do fine at 60 grams per hour for the entire race. A 4:00 to 5:00 marathoner, spending three or more hours on the road, has a stronger case for targeting closer to 90 grams per hour since their glycogen stores will be more depleted by the time they reach the later miles.
These numbers are not adjusted by body weight. Whether you weigh 130 pounds or 200 pounds, the limiting factor is how fast your intestines can absorb carbohydrates, not how large your muscles are. That absorption ceiling is a physiological bottleneck everyone shares, which is why recommendations are given as flat grams-per-hour targets rather than grams per kilogram of body mass.
Why Your Gut Has a Speed Limit
Your small intestine absorbs glucose through a specific transport channel that maxes out at roughly 60 grams per hour. No matter how much glucose you consume beyond that point, it sits in your gut unabsorbed, pulling water into the intestines and often causing cramping, bloating, or worse.
This is where fructose becomes useful. Fructose enters the bloodstream through a completely separate transport channel. By consuming a mix of glucose and fructose, you effectively open two lanes of absorption instead of one. Research on trained cyclists found that a glucose-fructose blend produced peak carbohydrate oxidation rates about 36% higher than glucose alone. That’s how athletes push past 60 grams per hour toward 90 or beyond without GI problems.
The ratio that appears most effective is roughly 0.8 parts fructose to 1 part glucose. Most commercial sports drinks and gels designed for endurance events already use a glucose-fructose or maltodextrin-fructose blend in roughly this range, so check the ingredient label rather than trying to engineer your own mix from scratch.
Can You Go Above 90 Grams?
A 2020 study tested elite mountain marathon runners at three intake levels: 60, 90, and 120 grams per hour. The group consuming 120 grams per hour reported lower perceived effort during the race and showed significantly less muscle damage markers in blood tests 24 hours afterward compared to both lower groups. The catch: these athletes had trained their guts to handle that volume before race day. The high intake wasn’t sprung on them cold.
For most recreational marathoners, 120 grams per hour is unnecessary and likely to cause stomach problems without dedicated preparation. But if you’re an experienced runner looking for marginal gains, it’s worth knowing the ceiling is higher than the traditional guidelines suggest, provided you put in the gut training work.
How to Train Your Gut
Your digestive system adapts to what you ask it to do. Runners who never eat during training runs and then try to take in 90 grams of carbs per hour on race day are almost guaranteed to have GI issues. The solution is progressive gut training in the weeks before your marathon.
Practice your race fueling strategy at least once per week during long runs. Start at a comfortable intake level, perhaps 40 to 50 grams per hour, and gradually increase over several weeks. Research from the Gatorade Sports Science Institute suggests that tolerance improves noticeably within 6 to 10 weeks of consistent practice. Even shorter dietary changes help: eating a high-carbohydrate diet for as little as two weeks increases the number of glucose transporters lining your intestinal wall, meaning your gut literally becomes better at absorbing fuel.
Use the same products you plan to race with. Gels, chews, and drinks all hit the stomach differently. Gels consumed without enough water create a concentrated solution that draws fluid into the gut, which is a common cause of nausea and cramping during races. If you use gels, chase them with 4 to 8 ounces of water.
What 60 to 90 Grams per Hour Looks Like
Putting these numbers into real food terms helps with planning:
- One typical energy gel contains 20 to 25 grams of carbohydrates
- A large sports drink bottle (20 oz) usually provides 30 to 40 grams
- Energy chews typically deliver about 25 grams per serving (3 to 4 pieces)
To hit 60 grams per hour, you might take one gel every 20 minutes, or combine a gel every 30 minutes with steady sips of sports drink. For 90 grams per hour, you’re looking at a gel plus sports drink every 20 to 25 minutes, which is a significant volume of intake. This is why practicing in training matters so much. The logistics of unwrapping, chewing, and drinking at race pace while your stomach is bouncing with every stride are genuinely difficult until they become routine.
Start fueling early in the race, ideally within the first 30 to 45 minutes. Your muscles are already burning through glycogen from the start, and waiting until mile 15 to begin eating means you’re playing catch-up with depleted stores. Steady, consistent intake from the beginning is far easier on the stomach than trying to cram calories in later.
Fluid and Sodium Alongside Carbs
Carbohydrate intake doesn’t exist in isolation. The ACSM recommends 400 to 800 milliliters of fluid per hour (roughly 13 to 27 ounces) depending on your sweat rate and the weather, along with 300 to 600 milligrams of sodium per hour for races lasting over two hours. If you’re getting most of your carbs from sports drinks, a good portion of your fluid and sodium needs are handled simultaneously. If you rely on gels and chews, you need to be more intentional about drinking water at aid stations and may want to add electrolyte tablets or salt capsules.
Concentrated carbohydrate solutions, anything above roughly 8% carbohydrate by volume, slow gastric emptying and increase the risk of GI distress. This is a practical reason to spread your intake across the hour rather than consuming a large bolus all at once. Small, frequent doses every 15 to 20 minutes keep the stomach moving without overwhelming it.