Energy gels are a core tool for endurance runners, developed to deliver fast-absorbed carbohydrates that fuel your performance late into a race. They help replenish your body’s limited glycogen stores, stave off energy dips, and promote steady pacing. For half marathons and marathons in particular, strategising when and how many gels to take can be the key to hitting your goals and avoiding “the wall.”

Energy gels typically contain simple sugars such as glucose, maltodextrin, or fructose designed for rapid digestion during exercise, often blended with electrolytes and sometimes caffeine for added effect. Their role is to provide a concentrated, portable energy source for runners and athletes engaged in prolonged or high-intensity efforts, especially as muscle glycogen depletes after around 90 minutes of steady exercise.

When to Start Taking Gels

• Most guidance suggests taking your first energy gel around 40-45 minutes into your half marathon.
• Continue taking a gel every 30-40 minutes afterwards for consistent energy.

How Many Gels is “Typical” for a Half Marathon?

• 2–4 gels during a half marathon is typical for most runners, depending on pace and finish time.
• Faster runners may only need two, those finishing around two hours may benefit from three to four gels to maintain carbohydrate intake.

Sample gel strategy for a 2-hour half marathon:

• Start: 0:00
• 1st gel: 00:40
• 2nd gel: 01:20
• Optional 3rd gel: 01:50 (for runners closer to 2 hours)
• Aim for 30–60g of carbohydrates per hour from gels and other sources (check label for carbs per gel, most contain 20–30g).

How Many Energy Gels for Full Marathons?

• The typical recommendation is 2–3 gels per hour during your marathon, starting from around 20–30 minutes in and repeating every 30–40 minutes thereafter.
• For a 4-hour marathon, that equates to 8–12 gels; for a 5-hour marathon, up to 15 gels may be reasonable at the upper end.

See our full range of recommended marathon supplements here.

To aid your half marathon and marathon training too, discover our marathon training plans to help you achieve your personal best.

• Taking gels “just in case” or doubling up won’t double your energy—in fact, it can result in an energy crash and gastrointestinal distress, including cramps, nausea, or diarrhea.
• Overuse also increases dental risks (due to high sugar and acidity) if not followed with water/rinsing.

• Gels are rarely needed for runs lasting under an hour (most 5K/10K events)—your body’s stored energy is typically sufficient.
• Gels can be used for slower 10Ks or if you are experimenting with longer effort, but your digestive system may not have enough time to process them for a performance boost.
• For these short runs, hydration and electrolytes are more important. Reserve gels for when you’re training/racing at 60–90 minutes or more.

Explore electrolytes, which come in single use sachets and perfect for those shorter distance runs.

Practice your gel strategy on training runs to see what your stomach tolerates, how soon you feel a benefit, and what flavors/textures work for you. Never experiment with a new gel or new timing on race day—always use your training to fine-tune what feels best. Try to take gels with water, not sports drink, to aid absorption and minimize digestive upset.

• Start your first gel 40-45 minutes in for a half marathon; repeat every 30–40 minutes.
• 2–4 gels for most half marathoners; 8–12 gels for marathoners finishing in 4 hours.
• Avoid doubling up; more is not better and can backfire.
• Gels aren’t needed for most runs under 1 hour — focus on hydration instead.
• Practice your plan in training for best results on race day.

With the right plan, energy gels are a powerful tool to help you run fast and finish strong through your next half or full marathon.