When to take gels while running is one of the most common questions I get as a nutritionist for runners. There is so much confusion around fuelling your runs. When to take gels, if you should take gels, when you actually need them—there are just so many questions.

Generally, you will have heard the “rules”: anything under 60 minutes, you don’t need anything. But 90 minutes is the key. When runs go over 90 minutes, you should be fuelling. But the big question is: is this too late or too soon?

This blog post is going to give you a definitive answer on when to take gels while running. We’re going to discuss distances, we’re going to discuss timing, and we’re going to bust some outdated myths to ensure you never “hit the wall” while you are running.

We are moving away from talking about running in miles and focusing on time-based fueling. Your body doesn’t define whether you have run five miles or ten miles; it generally depends on how long we’re running for and the intensity of that run.

Myth Busting: Why 90 Minutes is Too Late to Start Taking Gels When Running

When people ask when to take gels when running, the answer is not as simple as waiting until 90 minutes into your run. Let’s look at a little bit of the science (without getting too confusing!).

When we consume carbohydrates, they are absorbed into our bloodstream and stored as glycogen in our muscles and liver. Even when completely full, these stores only last 90 to 120 minutes. But remember: that relies on you starting your run with 100% of your glycogen stores completely full.

Research has shown that about 70% of our glycogen stores are used within that first 60 minutes of exercise¹. 

The Golden Rule of Timing:

You never want to leave fueling until you are out of energy, or nearly out of energy. It takes about 20 minutes from the moment you swallow a gel to when that fuel is actually available to be used by your body.

If you waited until the 90-minute mark to take your first gel, it would take until 110 minutes for that energy to hit your system. By then, you are super, super close to that 120-minute point where your glycogen stores are likely to be completely empty. This is often where runners “hit the wall”—that sudden, overwhelming feeling of heavy, lead-like legs and mental fog where your body simply runs out of accessible fuel.

By taking fuel on in advance, you allow your body to use the carbohydrates you are putting in, rather than just draining the stores that are already there.

Maximise Absorption: How Many Grams Do You Need?

Our body is limited in how much carbohydrate it can absorb within a given timeframe. To understand when to take gels when running effectively, you need to know about “Dual Fuel.”

• Glucose/Maltodextrin: This type of sugar is absorbed at a rate of around 60 grams per hour.
• Fructose: By adding a fructose-type sugar (think fruit sugars), we can boost absorption by another 30 grams per hour.

By combining these, your body can take on 90 grams of carbohydrates per hour. It’s like having two different transport systems.

Important Note on Weight: Research has shown that body weight plays no factor in this. Whether you are heavier or lighter, your intestines have a similar absorption limit. It is based purely on time.²

When choosing your fuel, check the ingredients for that two-to-one ratio of maltodextrin/glucose to fructose.

Fuelling for Weight Loss: Why Under-Fuelling Backfires

It is not uncommon for people to want to lose weight while running. I’ve definitely caught myself thinking: “I shouldn’t fuel my runs if I’m wanting to lose weight… why put calories in when I’m trying to burn them?”

But when we under-fuel our runs, it leads to:

• Low-quality sessions: You don’t get as much out of your training.
• Increased injury risk.
• Elevated cortisol levels: This can actually slow down long-term weight loss.

Forcefully putting your body into a massive caloric deficit during a run is where you run into issues. Fuelling correctly supports your weight loss goals by allowing you to train better and recover faster. It’s what you do the rest of the time that makes the biggest difference.

Time-Based vs. Distance-Based Fuelling: When to take gels while running

Run Length	Fuelling Strategy
Under 60 Mins	Generally, no gels are needed unless it’s a high-intensity session.
60 – 90 Mins	Optional 1 gel around the 45-minute mark. Single fuel source is fine
90 Mins – 2.5 Hours	Start fuelling at 20-40 minutes, then regularly from there depending on the carb content of fuel. Single carb sources are fine here
Start fuelling at the 20-40 minute mark, then regularly from there depending on the carb content of your chosen fuel. Here, you want that dual fuel source	Start fuelling at the 20-40 minute mark, then regularly from there depending on the carb content of your chosen fuel. Here you want that dual fuel source

Table outlining when to take gels when running

Tips for Mastering Your Race Day Hydration

Hydration is a non-negotiable. Taking a gel without water can invite the very GI issues we are trying to avoid.

Unless you are using Isotonic Gels (which are pre-mixed with a higher water content), you must take your gels with water. If you put too much concentrated carbohydrate into your system without enough fluid, your body will actually draw water from your bloodstream into your gut to try and process it. This is a one-way ticket to stomach cramps and unwanted toilet stops.

FAQ: Your Top Questions Answered

Should I fuel by time or distance?

Time. Your body measures physiological stress by duration, not miles covered. Miles can vary based on hills or effort, but time is a constant.

Do I need a gel for a 10k?

Generally, no. But if you are racing particularly hard or haven’t eaten, taking one about 20 minutes before you start can give you that glucose boost to start your run.

What if I forget and miss my gel time?

Take it immediately and then resume your new schedule. Don’t double up. Taking too much at once puts too much stress on your GI system.

What are isotonic gels?

These are gels pre-mixed with water. They are easier to consume if you don’t have immediate access to a water station.

How do I prevent stomach issues?

It comes down to practice. Your gut is a muscle that needs training just as much as your legs.

Take Your Fuelling to the Next Level

What more information around fuelling your runs then grab my FREE Ultimate Guide to Fuelling here.

Looking for more than a free download? Check out my services here to see how I can help you achieve your goals and finally feel confident fuelling your runs.

References

¹Jiménez-Alfageme, R., Garrone, F.P., Rodriguez-Sanchez, N., Romero-García, D., Sospedra, I., Giménez-Monzó, D., Ayala-Guzmán, C.I. and Martínez-Sanz, J.M., 2025. Nutritional Intake and Timing of Marathon Runners: Influence of Athlete’s Characteristics and Fueling Practices on Finishing Time. Sports Medicine – Open, [e-journal] 11 (1), pp.26. 10.1186/s40798-024-00801-w. <https://doi.org/10.1186/s40798-024-00801-w>.

²Jeukendrup, A., 2013. Multiple Transportable Carbohydrates and Their Benefits. Sports Science Exchange, [e-journal] 26 (108), pp.1–5. <https://www.gssiweb.org/docs/default-source/sse-docs/sse-108-jeukendrup.pdf?sfvrsn=2>.