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Energy gels are concentrated carbohydrate in a portable, fast-absorbing format. They’re the standard fuelling tool for runs over 60–75 minutes and virtually universal at half marathons and marathons. But choosing the right gel — and using it correctly — makes a significant difference to both performance and stomach comfort.
When Do You Need Energy Gels?
The body stores approximately 90 minutes of glycogen (carbohydrate energy) at moderate running effort. Beyond that point, carbohydrate from external sources is required to maintain pace.
Gels are necessary for: runs over 60–75 minutes at moderate-hard effort, half marathons, marathons, and trail races.
For runs under 60 minutes at easy pace, water is sufficient and gels are unnecessary.
How to Use Energy Gels
When to take the first gel: Start fuelling before you need it — approximately 45 minutes into the run, not when you feel the energy dropping. By the time you feel glycogen depletion (“bonking”), it’s too late for a gel to rescue the session.
Frequency: Every 30–45 minutes after the first gel. Most runners take 3–5 gels in a half marathon and 5–8 in a marathon depending on pace and individual needs.
With water: Gels are concentrated — take each one with 100–200ml of water to prevent nausea and ensure absorption. Never take a gel with a sports drink (both are concentrated carbohydrate; combined, they can cause significant GI distress).
Practice in training: Never use a new gel for the first time on race day. Test your chosen gel brand and flavour on long training runs before the race. Stomach tolerance varies significantly between individuals and products.
Best Energy Gels Available in the UK
1. SiS (Science in Sport) Go Isotonic Gels — Best for Beginners
– Carbs per gel: 22g
– Consistency: Liquid (no water required)
– Flavours: Orange, apple, tropical, lemon, cola
– Price: Approximately £1.50–1.80 each
– Where to buy: Widely available — Wiggle, Chain Reaction, Decathlon, Amazon
SiS isotonic gels are the most popular choice in UK running events and widely distributed at race aid stations. They’re thinner than most gels (no need for water) and easy on the stomach. Lower carbohydrate per gel than some alternatives, so you may need to take them more frequently.
2. Maurten 100 — Best for Sensitive Stomachs
– Carbs per gel: 25g
– Consistency: Thick (hydrogel technology)
– Flavours: Unflavoured (plain)
– Price: Approximately £3.50–4 each
– Where to buy: Wiggle, Running4Women, specialist running shops
Maurten uses hydrogel technology — the carbohydrate is encapsulated in a gel matrix that passes through the stomach more quickly, reducing GI issues. Used by elite marathon runners including Eliud Kipchoge. Expensive and unflavoured (which some runners find easier; others find unappealing).
3. Torq Energy Gel — Best Value Performance Option
– Carbs per gel: 28g (2:1 maltodextrin:fructose ratio)
– Consistency: Thick
– Flavours: Raspberry, rhubarb, guarana, orange, banana
– Price: Approximately £1.20–1.50 each
– Where to buy: Wiggle, Amazon, Running4Women
Torq gels use the 2:1 maltodextrin:fructose ratio shown in research to allow greater carbohydrate absorption than single-source carbs. Good value, decent flavours, and widely trusted in the UK endurance community.
4. Gu Energy Gel — Most Variety
– Carbs per gel: 22g
– Consistency: Thick
– Flavours: 25+ including Salted Caramel, Strawberry Banana, Vanilla Bean
– Price: Approximately £1.40–1.80 each
– Where to buy: Amazon, Wiggle, specialist running shops
American brand with the widest flavour range available in the UK. Some varieties contain caffeine (labelled clearly). The variety helps for long training blocks where flavour fatigue is a genuine issue.
5. Clif Shot — Best Caffeinated Option
– Carbs per gel: 24g
– Available with 25–50mg caffeine
– Consistency: Thick
– Price: Approximately £1.20–1.60 each
– Where to buy: Amazon, Wiggle, health food stores
Caffeine is one of the most evidence-backed legal ergogenic aids for endurance performance. A caffeinated gel 45–60 minutes before a race finish is a common strategy — take the caffeine gel at miles 8–9 in a half marathon for a late push.
Gel vs Chews vs Real Food
Gels: Fast absorption, portable, easy to take on the move. Best for races.
Chews (e.g. Clif Bloks, Gu Chews): Slower to eat, require more chewing — impractical at race pace but useful for long training runs at easier effort.
Real food (Medjool dates, banana, rice cakes): Some runners strongly prefer real food for long training runs. Works well at easy pace; less practical at race pace.
The rule: Use race conditions in training. If you’re racing with gels, train with gels.
Caffeine in Gels
Caffeine improves endurance performance in most runners — the evidence is consistent. Effective dose: 3–6mg per kg of bodyweight (approximately 200–400mg for a 70kg runner).
Practical approach for racing: 1 caffeinated gel (25–50mg caffeine) every 40–45 minutes from the midpoint of the race, or a single large dose (150–200mg) 45 minutes before the start.
Caveat: Caffeine affects GI motility — some runners find it increases urgency. Test in training, not on race day.
Summary
Best energy gels for UK runners:
- SiS isotonic gels are the most accessible starting point — no water needed, easy to find at UK race aid stations, gentle on the stomach
- Maurten is worth the premium if you have GI issues with other gels — hydrogel technology is the most significant gel innovation in recent years
- Take the first gel at 45 minutes, then every 30–45 minutes — fuel early, before you feel depletion, not after
- Always take gels with water, not sports drink — doubling up concentrated carbohydrate sources is the most reliable way to cause mid-race GI issues
- Test your race gels in long training runs — no new products on race day, ever