When to Take Energy Gel in a Race
Most runners who've bonked made the same mistake. Not a wrong product. Not the wrong dose. They waited too long.
By kilometre 30, energy is dropping, pace is drifting and the gel that goes in now is 15 minutes from making any real difference. The carbohydrate hasn't failed — the timing has. Energy gels are preventive tools, not rescue tools. The gap between those two things decides whether your race holds together or doesn't.
Knowing when to take energy gel in a race is as important as knowing which gel to take and how much carbohydrate it delivers. Get the timing right and the rest of the plan gets easier to execute. Get it wrong and even the best gel can't undo what's already been lost.
"The biggest timing mistake I see is athletes waiting until they feel they need a gel. By then they're chasing a glucose drop, not preventing one. I start taking fuel earlier than most people would consider necessary — within the first 20 minutes of a long race or hard effort. You're not fuelling for right now. You're fuelling for 45 minutes from now."
— Alistair Brownlee, Two-time Olympic Triathlon Champion and founder of truefuels
The physiology behind gel timing
When you run, you burn a mix of fat and carbohydrate. At marathon pace and above, carbohydrate becomes progressively more dominant. Muscle glycogen stores are limited — enough for roughly 90–120 minutes of racing, depending on pace and individual glycogen loading.
Blood glucose starts to drop before you feel it. By the time the sensation of fatigue, pace drag or mental fog arrives, glucose availability has already been compromised. Carbohydrate takes 15–30 minutes to fully enter the bloodstream and become available as fuel — faster with a 1:1 glucose-to-fructose gel like truefuels that activates both SGLT1 and GLUT5 transporters simultaneously, but still not instant.
That's the core timing principle: fuel for where you're going, not where you are.
When to take your first gel
The most common error in gel timing is treating the first gel as a rescue. The first gel should be taken before any signs of fatigue.
For most race distances, that means taking the first gel 20–30 minutes after the start, once breathing has settled and the gut is tolerating movement comfortably. Not because you're already depleted — you're not. Because the carbohydrate needs time to absorb, and you want it available when you enter the middle section of the race.
Gel timing by race distance
| Race distance | Typical race time | First gel at | Subsequent gels | Gels per hour |
|---|---|---|---|---|
| 10K | 40–60 min | 20–25 min | End of race if needed | 1 total (optional) |
| Half marathon | 1:30–2:30 | 20–25 min | Every 25–30 min | 1–2 |
| Marathon | 3:00–5:00+ | 20–25 min | Every 20–25 min | 2–3 |
| Triathlon bike | 2–5+ hours | 10–15 min in | Every 20 min | 2–3 |
| Triathlon run | 45 min–3+ hours | Start of run | Every 20–25 min | 1–2 |
| Ultra | 5+ hours | 20–30 min | Every 20–30 min | 2–3 variable |
At 40g per truefuels gel, 2 gels per hour delivers 80g of carbohydrate — within the 60–90g range where performance benefits are consistently demonstrated in the research. The 1:1 glucose-to-fructose ratio means both intestinal transporters are active simultaneously, which is what allows higher intake rates without the GI distress that comes from saturating the SGLT1 pathway alone.
How frequently to take gels
Even spacing works better than reactive dosing. Small, regular amounts every 20–30 minutes keeps carbohydrate delivery steady and avoids the stomach discomfort that can come from taking a large dose infrequently.
If your target is 80g per hour using 40g gels, that's one gel every 30 minutes. If you're pushing towards 90–120g/hour in a longer, harder race, you might take a gel every 20 minutes or combine with a carbohydrate drink. The schedule should be set before the race starts, not decided on the move.
Set a timer or use landmark cues — aid stations, kilometre markers, turn points. Under race stress, passive reminders fail. Structured ones don't.
What changes when pace and heat rise
At faster paces, carbohydrate burn rate increases. Your timing schedule should remain the same, but the consequences of missing a gel become more significant — there's less glycogen buffer and less margin for error.
In heat, the gut is under greater physiological stress. Blood flow to the digestive system decreases as the body prioritises thermoregulation. That means:
- Take gels slightly earlier than you otherwise would
- Always take with water (unless specifically designed otherwise) to aid gastric emptying
- Smaller doses more frequently are easier on a heat-stressed gut than larger doses less often
- The 40/1.0 truefuels variant becomes more relevant — the higher sodium supports both fluid retention and SGLT1 co-transport of glucose
Common gel timing mistakes that cost races
Taking the first gel only when energy drops. By then you've spent 15–20 minutes under-fuelled, and the carbohydrate you take now won't rescue that section.
Spacing gels too far apart and compensating with a larger dose. A 60g intake at one time is harder on the gut than two 30g takes at intervals.
Skipping a gel because the pace feels comfortable. Comfort now doesn't mean carbohydrate availability is fine. It means glycogen depletion hasn't progressed far enough to be felt yet.
Not practising the exact timing in training. If you've never taken a gel at 20 minutes into a race-pace effort, don't discover how your gut handles it on race day. Race rehearsal in training means the same products, the same timing, the same intensity.
Taking gel without water. Concentrated carbohydrate in the gut without fluid slows absorption and increases GI distress risk. Most gels, including truefuels, benefit from being washed down with water — or can be diluted into a drink if preferred.
Training your gut for race-day timing
The gut adapts. Consistently taking in carbohydrate at race-intensity intervals in training improves both tolerance and absorption efficiency over time. If you currently struggle with gels during high-intensity efforts, the answer is almost never to avoid them — it's to gradually habituate the gut through training.
Start with lower doses (one gel at 30 minutes into a long run), ensure adequate fluid intake, and build from there over several weeks. Record exactly what you took, when, with how much water and what the conditions were. This is performance data.
A simple rule to anchor everything
Start earlier than feels necessary. Stay consistent throughout. The worst moment to take a gel is the moment you most feel like you need one. The best moment is 20–30 minutes before that feeling arrives.
When timing is precise, the gel stops being an intervention and starts being part of a protocol you can trust. That's when race nutrition does its job quietly — supporting everything you've built in training, without needing to rescue anything.
