Carbohydrate gel for running: a coach's fueling protocol.

What a carbohydrate gel actually is

A carbohydrate gel for running is a small foil packet that holds about 20 to 30 grams of concentrated sugar, usually a mix of glucose (or maltodextrin) and fructose in a syrup base. You swallow it during a long run or race, chase it with a few sips of water, and your muscles have new fuel within roughly 15 minutes. Most gels also carry sodium, some carry caffeine, and a few carry electrolytes or amino acids on top. That is the whole product.

The reason gels exist is arithmetic. Your legs store roughly 90 minutes to two hours of glycogen at marathon effort. Any race or long run beyond that has to be topped up from your pocket, or you slow down. Real food (bananas, dates, rice cakes) can do the job, but it is heavier, harder to chew at pace, and slower to hit the bloodstream. Gels won the race for portable running fuel because they solved the packaging problem, not because they are magic. This is why running a marathon is as much a fueling problem as it is a training problem.

In 15 years of coaching, the biggest gel mistakes I watch runners make are not brand mistakes. They are dosage, timing, and gut-training mistakes. Fix those three and almost any reasonable gel will work for you.

How many gels per hour, and why 30 to 60 grams is the range

For any run beyond about 75 minutes, you want 30 to 60 grams of carbohydrate per hour. That is the range where a trained gut can absorb sugar as fast as your muscles are burning it, and where research on endurance fueling has landed across the last two decades. In practical terms, that is one gel every 30 to 45 minutes for most runners.

Where you sit inside that range depends on gut fitness, race effort, and body size. A newer marathoner running four hours can often manage 40 to 50 grams per hour. A trained runner racing near threshold under three hours can push toward 60 grams, sometimes a little more with practice. Under-shoot and you fade. Over-shoot without training the gut and you get the aid-station stop nobody wants.

Newer high-carb gels (60 to 100 grams per serving, glucose-plus-fructose blends) can push the ceiling to roughly 90 grams per hour, but only for runners who have deliberately trained their gut to it. Do not try that for the first time on race morning.

The biggest mistake: waiting too long for the first one

The single most common fueling error I see, across every level from first-time marathoner to sub-3 hopeful, is taking the first gel too late. Runners feel great through mile 10, decide they do not need it yet, and then take their first gel at mile 15 or 18. By then they are already draining.

The rule I give every athlete: first gel at 30 to 45 minutes in, no exceptions. Not when you feel you need it. When the clock says so. Feeling fine early is not information. By the time you feel empty, you are already 15 minutes past the point where eating would have helped.

Set the watch, set the interval, and take the gel whether or not your body is asking. About seven out of ten intermediate runners I coach cut two to five minutes off their marathon in the season after they started fueling earlier and more consistently, without changing a workout.

Training your gut is a training block of its own

Runners train their legs for four months and then wonder why their stomach quits at mile 20. The gut is a trainable organ. It responds to progressive overload the same way your calves do. Start under-fueled and it will stay under-fueled.

The gut adapts in two ways: it increases the transporter proteins that pull sugar out of your intestine, and it clears fluid from the stomach faster so gels do not slosh. Both adaptations take weeks. The runners who race with the smoothest stomachs are the ones who have taken 40 to 60 grams of carbohydrate on every long run over 90 minutes for the eight to ten weeks before race day, not the ones who saved their gels for the marathon. This is one of the small pieces of the coaching week that pays off completely out of proportion to how boring it looks written down.

A workable build:

• Weeks 1 to 3: one gel per long run, taken around minute 40. Learn the flavor, the texture, and how you swallow it at pace.
• Weeks 4 to 6: two gels per long run, roughly 40 minutes apart. Add a marathon-pace segment on one of the long runs so you are practicing under real effort.
• Weeks 7 onward: full race-day fueling on every long run over 90 minutes. Same gels, same timing, same drink you plan to use on race day.

Practicing race fueling sits right next to running easy days at genuinely easy pace on the list of things that pay off completely out of proportion to how boring they look on paper.

Gels vs chews, drinks, and real food

All four options deliver the same sugars in the end. The difference is how fast they land in the bloodstream and how easy they are to carry at pace.

• Chews match gels on carbs per serving but take longer to work through at pace, and they get annoying above threshold effort. Fine for easy long runs and slower ultras.
• Sports drinks hydrate and fuel at the same time. Useful when a race has predictable aid stations and the flavor is one you have practiced with. Unreliable when it is not, or when you finish a bottle and cannot get another for six miles.
• Real food (rice cakes, dates, boiled potatoes) works well at ultra distances where you have hours to digest between bites. In a marathon, the weight in your pockets and the chewing time cost more than the calories help.

How to pick a gel that actually works for you

Ignore most of the marketing. Three variables matter, and everything else is texture and taste.

1. Carbohydrate blend. A gel with both glucose (or maltodextrin) and fructose absorbs faster than a single-sugar gel because the two use different transporters. If the label lists only one sugar and you are running more than 90 minutes, keep shopping.
2. Consistency. Thicker gels are more concentrated but need more water to swallow safely. Thinner gels go down easier, especially in heat, but hit the stomach in more liquid. If you race in warm humid conditions, a thinner gel plus separate hydration usually works better than a syrupy one.
3. Caffeine. A single caffeinated gel in the back half of a marathon can help. Two in a row on a stomach that is not used to caffeine, or four across a race, will not. Practice caffeine dosing on training runs, not on race day.

What does not matter as much as the packaging suggests: brand, price, whether it is "natural," and whether it lists five other ingredients that sound performance-related (BCAAs, MCT oil, adaptogens). The sugars are doing the work.

The race-day fueling protocol

Race day is not the day to change anything. It is the day to execute the plan you already rehearsed. For a marathon, that plan usually looks like this:

Half marathon is simpler. For most runners, one gel about 15 minutes before the start and one around 45 minutes in is enough. If you are racing under about 90 minutes and you have carbo-loaded properly, you can often finish on the pre-race gel alone. For a 10K, most runners do not need in-race gels at all. A pre-race gel 15 minutes before the gun is optional but often helps. Whichever distance you race, the pace target itself should come from a recent number rather than a hope, and a VDOT-based estimate is the simplest way to get one.

The people who blow up at mile 22 have almost always made one of three mistakes: they took their first gel too late, they skipped one somewhere in the middle because they "felt fine," or they tried something new on race morning. All three are avoidable. None of them are about fitness.

What to do this weekend

You do not need a new brand or a new plan. You need a rehearsal.

1. Pick the gel you will race with. Buy three of them.
2. On your next long run over 90 minutes, take one at minute 40 and one at minute 75. Small sip of water with each.
3. Write down how you felt, how the gel went down, whether your stomach settled, and whether you faded in the last 20 minutes.
4. Repeat that setup for the next three long runs. If the stomach cooperates, add a third gel around minute 105.
5. Never introduce a new gel closer than three weeks to a goal race. If it worked in training, it will work on race day. If it did not, you now know before it counts.

The gels themselves are commodity products. What separates the runners who finish their marathon strong from the ones who walk from mile 22 is not a better packet. It is a rehearsed protocol. Get one written down, practice it, and it will still work when the mile markers stop feeling friendly.

Written by

Coach Johnny Crain

2:12 marathoner. 4× US Olympic Marathon Trials qualifier. 4× NCAA national champion and 4× NCAA runner-up. Spoke at the RRCA National Convention. Founder and head coach at RunFitCoach, where he coaches every athlete personally.