How to choose an energy gel

Educational content, not medical advice. Individual tolerance varies; persistent GI symptoms or any race-related medical concern should be reviewed by a sports dietitian or doctor.

There are maybe two hundred energy gels on the market and the marketing makes them sound completely different. They are not. Strip away the packaging and a gel is five numbers: how much carb, what kind of carb, how much sodium, how much caffeine, and what it costs per gram of carb. Once you can read those five numbers, the choice stops being a brand-loyalty question and becomes a matching exercise. This guide is how to read them.

If you would rather skip straight to filtering, our gel catalogue puts every gel we track side by side and lets you sort by carbs, sodium, caffeine, brand, or price. The rest of this guide is how to decide what to filter for.

1. Carb type decides your ceiling

This is the single most important attribute and the one labels bury. There are two families:

• Single-source (glucose, or maltodextrin, or "glucose syrup"). Absorbed through one intestinal transporter (SGLT1), which saturates at roughly 60 grams of carb per hour. Cheaper, simpler, and completely fine for anything under about two hours.
• Multi-transportable (a glucose-fructose blend, usually labelled 2:1 or 1:0.8). Fructose uses a second transporter (GLUT5), so the two together push the absorbable ceiling toward 90 grams per hour and beyond.

The rule that follows is simple. If your target intake is at or below 60 g/h, single-source is all you need and you should not pay extra for a fructose blend. If you are pushing past 60 g/h (long course, gut-trained, racing over two and a half hours) you must use a glucose-fructose gel or you will saturate, the carb will sit in your gut, and you will get the bloating that athletes blame on "too many gels" when the real problem was the wrong gel. The carbs-per-hour guide covers how to find your number; the gut-training guide covers the physiology.

The good news for long-course athletes is that the market has shifted this way: of the 300-plus gels in our catalogue, more than half are now glucose-fructose blends. The catch is that very few labels say so in plain language, which is why we classify each gel's carb type for you in the gel catalogue.

2. Carb dose sets how many you carry

Gels run from about 20 g to 40 g of carb each. This is pure logistics. A 40 g gel hitting 80 g/h means two gels an hour; a 22 g gel means closer to four. Over a five-hour race that is the difference between carrying ten sachets and carrying eighteen. Bigger-dose gels mean less to carry, fewer wrappers, fewer "did I take one?" moments, but they are also a bigger single bolus on your stomach. Match dose to how you like to fuel: steady sippers want smaller, frequent gels; set-and-forget athletes want the big ones.

You can sort the catalogue by carbs per gel directly, or see the highest-carb options on the most carbs per gel leaderboard.

3. Sodium is the attribute most people ignore

Most athletes choose a gel on carbs and caffeine and never look at sodium, then wonder why they cramp. Gel sodium ranges from near zero to over 200 mg per gel, a 40-fold spread. Whether you need the high-sodium ones depends entirely on your sweat: a heavy, salty sweater in the heat can lose over 1,000 mg of sodium an hour and should bias toward gels that carry their own sodium, while a light sweater in cool conditions is fine on the low-sodium ones and can get the rest from drink mix or tabs. Do not double-count: if your drink and your electrolyte tabs already cover sodium, your gel does not also have to. Work out your number with the sweat and sodium guide, then filter accordingly.

4. Caffeine is a yes/no, then a dose

Roughly two in five of the gels we track carry caffeine, usually 50 mg to 100 mg each. Caffeine is a genuine ergogenic aid (roughly 2-4% performance benefit at 3-6 mg/kg), but a gel is just a delivery vehicle for it, and three rules keep you out of trouble:

• Plan the total dose across the race, not per gel. A 70 kg athlete wants 210-420 mg total. If three of your gels are caffeinated at 100 mg each, that is your whole budget.
• Timing beats quantity. Caffeine peaks 45-60 minutes after you take it, so the caffeinated gel belongs before the part of the race that hurts, not at the finish.
• Most of your gels should be caffeine-free so you can place caffeine deliberately instead of dosing it by accident every time you fuel.

The caffeine guide has the full dosing protocol. When you shop, treat caffeine as a filter you toggle, and keep a non-caffeinated option in the mix.

5. Price per gram of carb is the number that compounds

A gel's sticker price is close to meaningless because the sachets hold different amounts of carb. The honest metric is cost per gram of carbohydrate, because carb is what you are actually buying. A 2.50-euro gel with 40 g of carb (6.3 cents/g) is cheaper fuel than a 1.80-euro gel with 22 g (8.2 cents/g), even though the second one looks cheaper on the shelf. Over a marathon build with 30-plus long runs, that gap is real money. Sort the gel catalogue by price, or compare your shortlist directly so the per-gram maths is done for you.

Putting it together: choose by race

These are starting points for a gut-trained athlete in temperate conditions. Adjust toward higher sodium for heat and heavy sweat.

Race	Carb type	Sodium bias	Caffeine
10K / parkrun	None needed; optional single gel pre-start	Low	Optional, pre-start
Half-marathon	Single-source	Low to moderate	One caffeinated, late
Marathon	Single-source, or glucose-fructose if over 3:30	Moderate	Two, placed deliberately
70.3 / long course	Glucose-fructose (2:1)	Moderate to high	Saved for the run
Ultra (4 h plus)	Glucose-fructose, mixed with real food	High	Used sparingly, late

A four-step buying process

1. Get your carb-per-hour number from the planner or the carbs-per-hour guide. That tells you single-source versus glucose-fructose.
2. Get your sodium-per-hour number from the sweat-sodium guide, and subtract whatever your drink already provides.
3. Filter the gel catalogue to that carb type and sodium range, toggle caffeine to taste, and sort by price per gram.
4. Put your top three in compare and pick on price and dose. Then, and this is non-negotiable, train your gut on the winner before race day. Never debut a gel in a race.

Compare before you commit

The whole point of NutriFinder is that you do not have to take any brand's word for it. Open the gel catalogue, filter to the numbers this guide told you to care about, add up to three to compare, and look at carbs, sodium, caffeine, and price in one table. If you want the carb target, sodium target, and a per-30-minute fuelling timeline for your specific race, the race-day planner builds it free, no signup for the first plan.

Research and references

The thresholds in this guide rest on the following peer-reviewed sources. Verify dose, side-effect profile, and contraindications against the primary literature.

1. Jeukendrup AE. 2014. Sports Medicine. A step towards personalized sports nutrition: carbohydrate intake during exercise. PMID 24791914
2. Burke LM, Hawley JA, Wong SHS, Jeukendrup AE. 2011. Journal of Sports Sciences. Carbohydrates for training and competition. PMID 21660838
3. Thomas DT, Erdman KA, Burke LM. 2016. Medicine & Science in Sports & Exercise. ACSM Joint Position Statement: Nutrition and Athletic Performance. PMID 26891166
4. Spriet LL. 2014. Sports Medicine. Exercise and sport performance with low doses of caffeine. PMID 25355191