Running Gels: How Many to Take and When in a Half Marathon and Marathon
Running gels are the most practical way to take carbs during a long race. The question is almost always the same: how many should I take and when? The answer depends on how long you will be running and how many grams of carbs each gel contains. This guide explains what the evidence says, how to work out your gels for a half marathon and a marathon, and how to take them without stomach problems.
Running gels: how many carbs you need per hour
The most cited guidance comes from Asker Jeukendrup, who matches the amount to the duration of the effort:
| Duration | Recommended carbs |
|---|---|
| About 1 hour | Small amounts or just a carb drink mouth rinse |
| 1 to 2 hours | Up to 30 g per hour |
| 2 to 3 hours | Up to 60 g per hour |
| Over 2.5 hours | Up to 90 g per hour, combining glucose and fructose |
Above 60 grams per hour you need to mix different sugars, such as glucose or maltodextrin with fructose, because the gut absorbs each one through a different pathway. I explain it in the guide to maltodextrin for runners.
Jeukendrup also notes that these amounts do not depend on body weight and may be lower when intensity is low.
How many grams are in a gel
It depends on the brand. Most contain 20 to 30 grams of carbs, and some reach 40 or more. Always check the label: the number of gels you need changes a lot depending on the one you use.
How many running gels to take in a half marathon
If you will take between 1:30 and 2:15, aim for about 30 grams per hour. With gels of about 25 grams, that means one or two gels:
- One around kilometre 8 or 10.
- Another around kilometre 15 if you will be running for more than 1:45.
If you run under 1:30, many runners get by with one gel or with what the aid stations offer.
How many running gels to take in a marathon
In a 3- to 4.5-hour marathon, a reference point is 60 grams per hour, or more if you have trained for it. With 25-gram gels, that means about two or three gels per hour:
- Start early, around kilometre 5 or 30 minutes, even if you are not hungry.
- Continue every 20 to 30 minutes.
- You can combine gels with the sports drink at aid stations to add carbs.
To calculate it with your own numbers, use the race carb calculator. Taking enough carbs is one of the best ways to avoid hitting the wall.
How to take running gels
- Take them with water, unless they are isotonic. A concentrated gel without water is more likely to upset your stomach.
- Try them first on long runs. Your gut can be trained; I explain it in the guide to training your gut.
- Do not try new gels on race day.
- If you use caffeinated gels, count the total dose; the guidelines are in the guide to caffeine for runners.
Common mistakes with running gels
- Waiting until you feel hungry or hit a low before taking the first one.
- Taking lots of gels at once in the second half to make up for it.
- Not checking how many grams of carbs each gel has.
- Trying 90 grams per hour on race day without having trained for it.
Conclusion
Running gels are calculated in grams of carbs per hour, not by number of gels. According to Jeukendrup, up to 30 grams per hour for efforts of 1 to 2 hours, up to 60 grams between 2 and 3 hours and up to 90 grams for longer efforts, combining glucose and fructose. In a half marathon one or two gels are usually enough; in a marathon, two or three per hour from the start. Always try them in training.
FAQ
How many gels should you take in a half marathon?
One or two gels of about 25 grams are usually enough, around kilometres 8-10 and 15.
How many gels should you take in a marathon?
It depends on the grams per gel and your time. A reference point is two to three 25-gram gels per hour, starting around 30 minutes.
When should you take your first gel?
In the marathon, around 30 minutes or kilometre 5. In the half marathon, around kilometre 8 or 10.
Should you take gels with water?
Yes, unless they are isotonic. Taking them with water makes them easier to digest.
Do you need running gels for a 10K?
No. In races of about an hour, you do not need carbs during the race.
