When to Take a Gel in a Marathon: Your First Gel and How Often
When to take a gel in a marathon: take your first one 30 to 45 minutes into the race, then one every 20 to 40 minutes depending on how many grams each gel holds and how many grams an hour you want. For most runners finishing between 3.5 and 5 hours, that works out to a gel roughly every 30 minutes.
That is the short version. The useful version depends on three numbers you can find in five minutes: the grams of carbohydrate on your gel’s label, your hourly target, and where the water stations sit on your course.
Why not wait until you feel tired?
Because a gel you swallow now does very little for the next few minutes, and its contribution keeps rising for hours. In a Birmingham lab study, cyclists took a glucose-fructose gel or the same sugars as a drink every 15 minutes for three hours. The share of energy coming from what they had swallowed climbed steadily and was still at its peak in the final minutes (Pfeiffer et al., 2010a). Starting early fills that pipeline before you need it.
The old warning against carbohydrate in the hour before a race doesn’t hold up either. Jeukendrup and Killer reviewed the pre-exercise studies and found performance was almost always unchanged or improved. Some people do feel shaky or light-headed, rarely with genuinely low blood glucose, so test it in training rather than on race morning (Jeukendrup & Killer, 2010).
Practical upshot: a gel 5 to 15 minutes before the gun is fine if your stomach likes it. A gel at 30 to 45 minutes is the first one that counts.
How often after the first?
Work it out from grams, not from habit. Divide your hourly target by the carbohydrate per gel, and that tells you how many gels an hour. The hourly targets come from the ACSM joint position statement and Jeukendrup’s duration guidelines: 30 to 60 g an hour for one to two and a half hours, up to 90 g beyond that if your gut is trained (Thomas et al., 2016; Jeukendrup, 2014). We cover where those numbers come from in How Many Carbs Per Hour Do You Need for Running?
| Gel size | 40 g/hour | 60 g/hour | 90 g/hour |
|---|---|---|---|
| 20 g carbohydrate | Every 30 min | Every 20 min | Gels alone get impractical; add drink |
| 25 g carbohydrate | Every 37 min | Every 25 min | Every 17 min, or gels plus drink |
| 30 g carbohydrate | Every 45 min | Every 30 min | Every 20 min |
| 40 g carbohydrate | Every 60 min | Every 40 min | Every 27 min |
Two things the table hides. First, a cup of isotonic drink at an aid station is carbohydrate too, so it lets you stretch the gap between gels. Second, the 90 g column assumes your gel mixes glucose (or maltodextrin) with fructose. A glucose-only gel hits an absorption ceiling around 60 g an hour, and the extra sits in your gut (Jeukendrup, 2014).
What do most marathoners actually manage?
Less than they plan. When researchers surveyed athletes after real races, marathon runners averaged about 35 g of carbohydrate an hour, well below triathletes and cyclists at 53 to 71 g (Pfeiffer et al., 2012). Running jostles the stomach, cups are hard to drink from at pace, and gels get skipped when an aid station is crowded.
The same survey found the strongest predictor of stomach trouble during a race was a history of stomach trouble. Higher carbohydrate intake was linked to more nausea and wind, but also to faster finishing times in the Ironman races. Read that as: practise the amount, don’t avoid it.
If you have been taking one gel at 10K and another at 30K, moving to a gel every 30 minutes is a big jump. Make it over four to six long runs, adding one gel per run. Ricardo Costa’s Monash group showed two weeks of repeated gut-challenge sessions cut gastrointestinal symptoms by about 60% (Costa et al., 2017).
Do you need water with every gel?
Yes, ideally a few mouthfuls. In the Pfeiffer gel study, the gel was oxidised as well as the drink, but the gel group was also drinking plain water at the same fluid rate as the drink group, about 870 ml an hour (Pfeiffer et al., 2010a). The gel worked because water went down with it.
A concentrated gel on a dry mouth sits heavier and slower. In Malaysian heat you are already fighting a stomach that empties less willingly. The Sports Dietitians Australia position statement on exercise in hot conditions flags heat stress as a cause of gut disturbance, which is one more reason to wash gels down (McCubbin et al., 2020).
So schedule gels around water stations, not around round numbers on your watch. Take the gel 100 to 200 metres before the station, then drink. If your watch says 2:00 but the next table is 800 metres away, wait.
A worked plan: Penang Bridge Marathon, 4:40 finish
The Penang Bridge International Marathon 2026 is on 13 December, starting from Aspen Vision City in Batu Kawan (The Star, 2026). Like most Malaysian city marathons, the back half of the race is run as the sun climbs and the humidity stays high. Check the official race guide for the exact start time and water station kilometres, since those decide the plan below.
Take a runner aiming for 4:40, targeting about 50 g an hour, carrying 25 g gels:
- Breakfast, 2.5 to 3 hours before: a familiar carbohydrate meal. Bread and kaya, or plain rice with something light. Not nasi lemak with extra sambal.
- 10 minutes before the start: optional gel, with water, if you’ve practised it.
- From 0:40: one 25 g gel every 30 minutes, each one timed to the nearest water station. That is about eight gels to the finish.
- Between gels: a cup of isotonic drink at alternate stations, which adds roughly 10 to 15 g each time. Count it.
- After 3:30: if gels start to taste awful, swap one for two cups of isotonic. Don’t drop carbohydrate altogether.
Eight gels is a lot of pocket space. A race belt with gel loops, or a few in a short-tights back pocket, works better than one bulging vest pocket. For the fluid and sodium side of the same race, see How Much Sodium Do Runners Need Per Hour?, and put your own numbers into our race fueling calculator to get race-day totals.
What changes for a half marathon or shorter?
Below about 75 minutes, you don’t need gels for fuel. A carbohydrate mouth rinse has improved performance in one-hour cycling time trials and increased distance covered in a 30-minute treadmill run, even though participants spat it out (Carter et al., 2004; Rollo et al., 2008). The effect appears to come from signals in the mouth to the brain, not from energy reaching the muscles.
For a half marathon taking 1:45 to 2:30, one or two gels is plenty: one at about 40 minutes, a second at about 80 minutes if you’re out past two hours. On a hilly half, where climbing slows everyone down and pushes finishing times up, lean towards the second.
And for a trail race or ultra?
The same logic applies, but time replaces distance and real food takes over from gels after a few hours. On long climbs you’re hiking and burning carbohydrate more slowly, so gels can come a little less often. On runnable descents, stay on schedule. A gel alarm on your watch every 30 or 40 minutes beats relying on memory at hour seven. Our ultra marathon nutrition guide covers how gels, rice balls and aid station food fit together over 50K to 100K.
Quick answers
Can I take two gels at once if I missed one? Better not. Doubling up puts 50 to 60 g into your stomach in one go, which is exactly what causes trouble. Take the missed one now and push the next one back.
Should I take a caffeine gel first? Most runners save caffeinated gels for the second half, when fatigue builds. Whatever you choose, try it in a long run first, because caffeine upsets some stomachs.
Gels are only one part of a hot-weather race. For the bigger picture on fluid and electrolytes, start with our running electrolytes and hydration guide, and for race-by-race plans, browse our Malaysian race nutrition guides.
References
- Pfeiffer B, Stellingwerff T, Zaltas E, Jeukendrup AE (2010a). CHO oxidation from a CHO gel compared with a drink during exercise. Medicine & Science in Sports & Exercise, 42(11), 2038-2045. doi:10.1249/MSS.0b013e3181e0efe6
- Jeukendrup AE, Killer SC (2010). The myths surrounding pre-exercise carbohydrate feeding. Annals of Nutrition and Metabolism, 57(Suppl 2), 18-25. doi:10.1159/000322698
- Thomas DT, Erdman KA, Burke LM (2016). American College of Sports Medicine joint position statement: nutrition and athletic performance. Medicine & Science in Sports & Exercise, 48(3), 543-568. doi:10.1249/MSS.0000000000000852
- Jeukendrup A (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), S25-S33. doi:10.1007/s40279-014-0148-z
- Pfeiffer B, Stellingwerff T, Hodgson AB, et al. (2012). Nutritional intake and gastrointestinal problems during competitive endurance events. Medicine & Science in Sports & Exercise, 44(2), 344-351. doi:10.1249/MSS.0b013e31822dc809
- Costa RJS, Miall A, Khoo A, et al. (2017). Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Applied Physiology, Nutrition, and Metabolism, 42(5), 547-557. doi:10.1139/apnm-2016-0453
- McCubbin AJ, Allanson BA, Caldwell Odgers JN, et al. (2020). Sports Dietitians Australia position statement: nutrition for exercise in hot environments. International Journal of Sport Nutrition and Exercise Metabolism, 30(1), 83-98. doi:10.1123/ijsnem.2019-0300
- Carter JM, Jeukendrup AE, Jones DA (2004). The effect of carbohydrate mouth rinse on 1-h cycle time trial performance. Medicine & Science in Sports & Exercise, 36(12), 2107-2111. doi:10.1249/01.mss.0000147585.65709.6f
- Rollo I, Williams C, Gant N, Nute M (2008). The influence of carbohydrate mouth rinse on self-selected speeds during a 30-min treadmill run. International Journal of Sport Nutrition and Exercise Metabolism, 18(6), 585-600. doi:10.1123/ijsnem.18.6.585
- The Star (8 October 2026). Go the distance: limited slots open for full Penang Bridge marathon until Oct 11. thestar.com.my
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