How Long for Energy Gel to Work?

If you’re a long-distance runner, cyclist, or triathlete, you already know the importance of fuelling your body properly during exercise. Hopefully you didn’t have to learn the hard way! Energy gels are a popular choice for quick and convenient energy, but a common question among endurance athletes is: “How long does it take for an energy gel to work?”

Understanding how energy gels work, how quickly they start to take effect, and the best way to use them is essential for optimising your performance. Taking one at the right moment can make all of the difference when it comes to getting over the line.

That’s why we’re breaking down everything you need to know about timing your gels, so you can fuel smarter, avoid fatigue, and cross that finish line strong.

But first - for those who are new to the idea, why does this matter?

Let’s jump right in:

What Are Energy Gels and Why Are They Important?

Energy gels are small sachets of concentrated carbohydrates designed to provide a rapid energy boost during prolonged exercise.

They’re typically made with simple sugars like glucose, fructose, or lower quality maltodextrin, making them easy for the body to absorb and convert into energy.

Some energy gels also include additional ingredients such as electrolytes (such as sodium and potassium) to help replace minerals lost through sweat, and caffeine for an extra performance boost.

During endurance activities, your body burns through glycogen – the stored form of carbohydrates in your muscles and liver. Once these stores start to run low, fatigue sets in. Energy gels help delay this fatigue by quickly replenishing blood glucose levels.

To read more about this, check out our more general post on energy gels.

If you’re already up to speed on the basics, just keep reading:

How Do Energy Gels Work in the Body?

When you consume an energy gel, here’s what happens:

The gel enters your stomach and mixes with gastric juices.
Carbohydrates in the gel pass into the small intestine, where they’re broken down and absorbed into the bloodstream.
Your blood sugar levels rise, delivering an immediate source of energy to working muscles.
This helps maintain your pace and stave off fatigue during long runs or rides.

The simplicity of the sugars in energy gels means they don’t require much digestion – they’re usually absorbed much more quickly than the complex carbohydrates found in whole foods.

So, How Long for an Energy Gel to Work?

For most athletes, energy gels start making a noticeable difference to energy levels within 5 to 15 minutes after consumption. This window depends on several factors:

Your metabolism – Everyone digests and absorbs sugars at slightly different rates.
How hydrated you are – If you’re dehydrated, digestion slows down, and the gel may take longer to kick in.
Caffeine content – Caffeine can slightly speed up how quickly you feel energised.
Exercise intensity – During high-intensity exercise, blood flow is prioritised to your muscles, which can slightly slow digestion.

Protein Rebel Key Tip: Drinking some water shortly after having a gel (around 200–300ml) can help to move them out of the stomach and into the small intestine faster, leading to quicker absorption.

When Should You Take an Energy Gel?

Timing is everything when it comes to energy gels. The goal is to stay ahead of fatigue, rather than trying to recover once you’re already feeling drained.

Given that you need to wait for your gels to “kick in”, taking them when fatigue starts to kick in, is likely to be already too late. By taking them early enough and at the right time, you can often prevent this from happening at all.

Here’s a general energy gel timing guide:

For shorter runs under 60 minutes: You probably don’t need an energy gel – your body has enough glycogen stored. You may still find them helpful if you’re still getting used to this kind of distance, but take them early on to prevent the full benefit kicking in after you’re done!
For medium runs of 60–90 minutes: If it’s at a moderate-to-high intensity, consider taking 2-3 gels per hour to support your glycogen levels in the later stages.
For longer runs 90 minutes or more (like marathons): Take your first gel at 45 minutes. Continue to consume 2-3 gels per hour after that.
For very long runs of 3 hours plus (like ultramarathons, triathlons and more): Follow the previous tip, but consider taking even more often if needed. Also at these distances it is best to mix in some whole foods too.

This strategy keeps your blood sugar levels steady and your glycogen topped up, delaying the “bonk” or “hitting the wall” that can derail your performance.

Examples of Energy Gel Timing

Here’s how it might look for a few common events:

Marathon:

Every 30 mins

100km cycle ride:

45 mins – 1st gel
2-3 gels per hour for the rest of the ride

Triathlon (Half Ironman distance):

After the swim (before the bike leg) – 1st gel
2-3 per hour on the bike
2-3 per hour in the run leg.

Why Is It Important to Practise with Energy Gels?

Every energy gel causes a slightly different reaction. While natural energy gels can be easily tolerated, others, especially more budget gels by major brands can cause gastrointestinal discomfort like cramping, bloating, or diarrhoea.

Practising with gels during training allows you to:

Work out how many gels your stomach can handle.
See how quickly your body absorbs them.
Find your preferred gel brand and flavour.
Train your gut to absorb carbohydrates more efficiently.

How to Choose the Right Energy Gel

There’s a huge variety of energy gels on the market, and finding the best one for you can take a bit of trial and error. Here are a few things to consider:

Carbohydrate type: Some gels use only glucose, others use a mix of glucose and fructose. Research suggests that a glucose–fructose mix such as that found in natural maple syrup can increase carbohydrate absorption and improve performance.
Caffeine content: Caffeinated gels can boost focus and reduce perceived exertion. If you’re sensitive to caffeine, go for caffeine-free gels.
Ingredients: Some budget gels made by big brands to turn a profit tend to contain low quality filler and other nasty, unhelpful ingredients, or low quality forms of carbs like maltodextrin. Higher quality gels will use less ingredients and more easily digestible forms of carbohydrate.
Company: Choose a company you are happy to support, such as one that is part of the running community and supports runners, as opposed to a large corporation who simply creates gels to turn a profit.

Hydration: Why It’s Essential When Taking Energy Gels

Energy gels are a concentrated source of sugar. Taking them while dehydrated can:

Slow down absorption in the stomach.
Increase the risk of stomach cramps or bloating.
Leave you feeling thirsty or dehydrated.

Always aim to take energy gels with at least 200–300ml of water. This not only speeds up digestion but also helps replace fluids lost through sweat.

Factors That Affect How Long It Takes for Energy Gels to Work

Let’s recap and expand on what influences energy gel effectiveness:

Hydration levels: Dehydration slows gastric emptying, so staying hydrated is key.
Body temperature: In hot conditions, blood is redirected to the skin to help cool you down, slightly slowing digestion.
Exercise intensity: Very intense efforts can divert blood away from your stomach, slowing digestion a little.
Caffeine sensitivity: Caffeine speeds up how you feel energised but can also cause GI distress for some.
Type of gel: Gels with easily digestible sugar sources tend to absorb faster.

Common Mistakes to Avoid with Energy Gels

We’ve not only been around the block when it comes to running ourselves, but we’ve worked with countless runners of all levels. Here are some of the most common pitfalls to avoid:

Taking gels too late: If you wait until you’re already exhausted, it’s hard to catch up, and sometimes the boost of energy won’t come until after you’re done running. Start fuelling early and consistently.
Not using water: Gels need water for proper absorption. Even if that wasn’t true, a dehydrated runner isn’t a good runner. Don’t skip it!
Using too many gels: More isn’t always better – stick to 1–3 per hour, depending on your energy needs and what you’ve practised in training.
Trying a new gel on race day: Always test new gels during training first. If you’ve purchased one that doesn’t agree with you, halfway through race day isn’t the time to find out!

Mastering Your Energy Gel Strategy

Energy gels can be a game-changer for endurance athletes, providing a rapid energy source when your body needs it most.

For most runners and cyclists, they start working within 5–15 minutes – but to get the most out of them, you need to remember what we’ve covered today:

Start fuelling early, 10-15 minutes before starting is a good idea (don’t wait for fatigue to set in).
Take 2-3 gels per hour during longer efforts.
Always practise in training and take gels with water, or at least drink often.
Find the brands that work best for you, but start with those that offer fewer ingredients and natural sources of energy such as maple syrup.

By mastering your energy gel strategy, you’ll keep your energy levels steady, and power through to the finish line feeling strong and energised!

Want more endurance nutrition tips?

Check out our guides on:

At Protein Rebel, we create natural, high quality running supplements with as few ingredients as possible, allowing for easy digestion and a huge boost to your ability to perform, improve and recover.

Our running gels are made in the UK from premium ingredients and contain zero unhelpful filler, additives or bulking agents.

You can learn more about why runners love them by clicking below:

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