Triathlon is the only endurance sport where you have to eat and drink across three completely different disciplines, each with its own rules about what your gut will tolerate. You can't sip a bottle mid-swim, you can shovel in real carbohydrate on the bike, and by the time you hit the run your stomach is often in open revolt. Getting fuelling right isn't a nice-to-have — it is frequently the difference between a strong negative split and a death-march finish where you're walking the aid stations and wondering why your legs stopped answering.
This triathlon nutrition guide breaks down what to eat and drink before, during and after each leg, with the actual numbers that matter rather than vague advice to "stay topped up". Whether you're racing your first sprint or your third full-distance, the underlying physiology is the same: you have roughly 90 minutes of stored glycogen at race intensity, and everything you do with nutrition is about stretching that reserve and defending your gut so it keeps absorbing fuel when it counts.
Quick answer: aim for 60g of carbohydrate per hour for triathlons up to around three hours, rising to 80–90g per hour for long-course racing with a trained gut and a glucose-fructose blend. Eat breakfast three to four hours before the swim, bank the bulk of your calories on the bike, then switch to small, frequent doses on the run. Alongside the carbs, drink 500–750ml of fluid per hour with electrolytes — and rehearse all of it in training first.
How Many Carbs Per Hour Do Triathletes Actually Need?
The single most important number in any triathlon nutrition guide is carbohydrate intake per hour. Your working muscles can only draw on so much stored glycogen, and once it's gone, your pace falls off a cliff. For efforts under about 90 minutes — a sprint triathlon for most people — you can largely race on what you started with, plus a bit of topping up. For anything longer, you need to be taking on fuel continuously.
The current evidence points to 60g of carbohydrate per hour as the workable target for events up to around three hours, rising to 80–90g per hour for long-course racing in athletes who have trained their gut to handle it. The key limiter is absorption: your intestine can only shuttle glucose across at roughly 60g per hour before the transporters saturate. This is why fuels that combine glucose and fructose in roughly a 2:1 ratio matter — fructose uses a separate transporter, letting you push total intake higher without the sloshing, bloated feeling that ends so many races.
Practically, that means planning your intake in advance rather than eating on feel. A 5-hour half-distance race at 70g per hour is 350g of carbohydrate you need to carry, calculate and consume — not something you can improvise at mile 40.
Fuelling Each Leg: Swim, Bike and Run
The swim is the one leg you can't fuel during, so it's all about what you did beforehand. Eat your pre-race breakfast three to four hours out — something like porridge with banana and honey delivering 100–150g of carbohydrate — then take a gel or a handful of chews 10–15 minutes before the gun so it hits your bloodstream as you enter the water. Don't experiment here; race morning is not the day to try a new breakfast.
The bike is your feeding station. You're in a stable position, your heart rate is lower than on the run, and your gut has its best chance of absorbing food. This is where you bank the bulk of your calories. Start eating within the first 15 minutes rather than waiting until you feel empty — by the time you notice hunger or fading legs, you're already behind. Alternate between carbohydrate sources and keep sipping an electrolyte drink. On a long-course bike leg, aim to leave T2 having taken on the majority of your hourly carbohydrate target so the run becomes about topping up, not catching up.
The run is where digestion is hardest. The jolting motion, the redirected blood flow and the accumulated fatigue all conspire against your stomach. Shift towards fuels that go down easily — smaller, more frequent doses work better than a single big hit. Many triathletes switch to cola or a fast gel here, but easily chewed, portable fuel that doesn't require a big gulp of water can be gentler. Take on a little at every aid station and keep the electrolytes coming, especially in heat.
Here's the whole race on one page:
| Leg | Fuelling approach | Key numbers |
| Pre-race & swim | Breakfast 3–4 hours out; a gel or a few chews 10–15 minutes before the gun. Nothing new on race morning | 100–150g carbs at breakfast |
| Bike | Your feeding station: start within 15 minutes, alternate carb sources, sip electrolyte drink, bank the bulk of your calories before T2 | 60g carbs/hour (80–90g/h long course, gut-trained) |
| Run | Small, frequent doses of easy-to-digest fuel at every aid station; keep the electrolytes coming, especially in heat | Little and often — top up, don't catch up |
| Recovery | Carbohydrate plus protein within 30–60 minutes of finishing | ~1g carbs/kg body weight + 20–25g protein |
Hydration and Electrolytes: The Other Half of the Equation
Carbohydrate gets the attention, but dehydration and sodium loss end just as many races. Aim to replace fluid at a rate that keeps body-mass loss under about 2–3% — for most athletes that's 500–750ml of fluid per hour, adjusted up in heat. More important than volume alone is sodium: sweat contains roughly 500–1,000mg of sodium per litre, and in a long, hot race you can lose several grams. Replacing it prevents the muscle cramping and that hollow, wrung-out feeling that creeps in late on.
A simple rule: if your fuel is delivering carbohydrate, make sure your drink is delivering electrolytes, and don't rely on plain water alone for anything over two hours. Weigh yourself before and after long training sessions to learn your personal sweat rate rather than guessing — it varies enormously between athletes.
Race fuel your stomach can handle
Small glucose-fructose pastilles — take a couple at a time, even on the run. Two chews deliver roughly 30g of carbs.
What We Use at FTP Endurance Fuel
We built our energy pastilles because so much triathlon fuel is either a sickly gel that's hard to stomach by hour four, or a bar you can't chew when you're breathing hard. Our pastilles use a glucose-fructose blend so you can absorb more carbohydrate per hour without the gut distress, and they're small enough to take a couple at a time — which is exactly what you want on the run when a whole gel feels like too much.
The Mixed Fruit Pastilles are our go-to for the bike leg, where variety keeps flavour fatigue at bay over a long ride. For the recovery side, the Tart Cherry Pastilles deliver anthocyanins, which help reduce the oxidative stress and inflammation that a hard triathlon leaves behind. If you're new to the brand, the taster pack is a low-risk way to test how they sit in your stomach during training before you commit to race day.
Don't Forget Recovery and Practice
The race doesn't end at the finish line, especially if you're training through a season with events close together. Within 30–60 minutes of finishing, aim for a mix of carbohydrate and protein — around 1g of carbohydrate per kg of body weight plus 20–25g of protein — to refill glycogen and start muscle repair. This window matters most when your next hard session is within a day or two.
Above all, nothing new on race day. Every gel, chew and drink you plan to use should be rehearsed in training at race intensity, so your gut is trained to absorb fuel while your legs are working hard. The best triathlon nutrition plan is the boring one you've practised a dozen times and know works.
Frequently Asked Questions
How many carbs per hour should I eat in a triathlon?
Target 60g of carbohydrate per hour for events up to around three hours, rising to 80–90g per hour for long-course racing if you've trained your gut. The upper end is only realistic with a glucose-fructose blend, because fructose uses a separate intestinal transporter to glucose and lifts your total absorption ceiling.
What should I eat before a triathlon?
Eat a familiar carbohydrate-based breakfast three to four hours before the start — something like porridge with banana and honey delivering 100–150g of carbohydrate — then take a gel or a handful of chews 10–15 minutes before the gun so it hits your bloodstream as you enter the water. Never experiment on race morning.
How do I avoid stomach problems on the run leg?
Bank the bulk of your calories on the bike so the run is about topping up rather than catching up, then switch to smaller, more frequent doses of easy-to-digest fuel — a couple of chews at a time rather than a whole gel. Take a little at every aid station, keep electrolytes coming, and train your gut at race intensity beforehand.
What should triathletes drink during a race?
Aim for 500–750ml of fluid per hour, adjusted up in heat, and make sure it carries electrolytes rather than relying on plain water for anything over two hours. Sweat contains roughly 500–1,000mg of sodium per litre, and replacing it prevents the cramping and hollow feeling that creeps in late in a race.
Dial in your carbohydrate target, defend your hydration and sodium, and treat your gut as a trainable organ, and you'll arrive at the run with something left in the tank. Ready to test your race fuel? Explore our taster pack and find what your stomach loves before your next start line.
Mixed Fruit Pastilles 1kg
Our go-to for the bike leg — a glucose-fructose blend in three rotating flavours.
£44.99
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Electrolyte Tablets
Cherry-flavour tablets to cover the sodium side of your race plan.
£5.99
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