A Runner's Guide to Mastering Race Day Fueling: How often should I take gels in a marathon?

October 28, 2025 •

3 min read

Science shows that the body's glycogen stores, its primary fuel for endurance, can be depleted in as little as 90 minutes of running. Learning exactly how often should I take gels in a marathon is crucial to topping off these reserves, preventing the dreaded 'bonk,' and sustaining your energy to the finish line.

Quick Summary

Proper fueling with energy gels is vital for marathon performance by maintaining glycogen levels. The ideal frequency depends on your personal needs, pace, and gut tolerance, with a common guideline being every 30-45 minutes. A successful strategy involves consistent intake based on your practiced plan.

Key Points

Start Early: Begin taking gels 60 to 90 minutes into your marathon to start replenishing glycogen before your stores are depleted, not after you feel tired.
Aim for Consistency: A common and effective frequency is one gel every 30 to 45 minutes to maintain steady blood glucose levels and prevent energy crashes.
Hydrate with Water: Always consume water alongside your gel (unless it's isotonic) to help with digestion and absorption and prevent stomach upset.
Practice During Training: Test different gels and timing strategies during your long runs to train your gut and find what works for you before race day.
Consider Your Pace and Size: Your optimal intake rate is individual and depends on your effort level and body mass. Faster runners generally need more carbohydrates per hour.
Listen to Your Body: While a plan is important, be prepared to adapt based on how you feel. Signs of nausea or cramping may indicate you need to slow down your fueling.
Never Experiment on Race Day: Stick to the gels and fueling plan you have successfully rehearsed during your training runs to avoid unwanted surprises.

Understanding the Science of Marathon Fueling

During a marathon, your body relies primarily on carbohydrates stored in your muscles and liver, known as glycogen, for energy. These stores are limited and can deplete after 60 to 90 minutes of running, leading to reduced performance or 'hitting the wall'. Energy gels offer a concentrated and convenient source of carbohydrates to replenish these stores and provide a quick energy boost. Effective fueling depends on proper timing and frequency of gel intake.

Factors That Influence Your Gel Schedule

An individualized gel strategy is essential as needs differ among runners. Key factors include:

Body Weight and Size: Larger runners typically require more fuel.
Running Pace and Intensity: Higher intensity running increases carbohydrate use, so faster runners may need more frequent intake.
Gut Training and Tolerance: The digestive system can be trained to handle more carbohydrates during exercise. Testing gels during training is crucial to avoid gastrointestinal issues.
Environmental Conditions: Heat and humidity affect hydration and can impact how effectively your body processes carbohydrates.

The Standard Gel Timing Strategy

A common recommendation is to take one gel every 30 to 45 minutes after the first 60 to 90 minutes of running. This helps maintain consistent blood sugar levels and energy. Most gels provide 20-30 grams of carbohydrates, aligning with general recommendations of 30-60 grams per hour for endurance events.

First Gel: Consume the first gel around the 60-minute mark to proactively maintain energy levels.
Subsequent Gels: Stick to a regular schedule, using a timer if needed, rather than waiting for fatigue.
Pre-Race Gel: Some runners take a gel 10-15 minutes before the start, particularly if their last meal was long ago. Practice this in training to see how your body responds.

The Critical Role of Hydration

Taking gels with water is vital. Gels are concentrated and need fluid for proper digestion and absorption. Without water, they can cause stomach upset. Plan to take gels near aid stations or carry water. Be mindful of carbohydrate content if using electrolyte drinks alongside gels.

Comparison of Different Fueling Approaches


Fueling Strategy	Carbohydrate Intake	Gel Frequency	Best For	Potential Downsides
Standard	30-60g/hour	One gel every 30-45 min	Most runners, all distances over 90 min	Requires consistent intake and good hydration
High-Carb	60-90+g/hour	One gel every 20-30 min	Faster, elite runners; gut-trained athletes	High risk of GI issues if not properly practiced
Conservative	<30g/hour	One gel every 45-60 min	Slower runners, lower intensity; sensitive stomachs	Risk of under-fueling and 'bonking' later in the race
Mixed Source	30-60g/hour	Combined with sports drinks and chews	Runners who want variety or can't tolerate many gels	Can be complex to manage total carbohydrate intake

Training Your Gut for Race Day

It's crucial to never try anything new on race day. Practice your fueling strategy during long training runs to train your digestive system and identify suitable gels and timing. Mimic race conditions during these practice runs.

Potential Gel-Related Issues and How to Solve Them

Be prepared for potential issues during the race:

Gastrointestinal (GI) Distress: Cramps or nausea can result from inadequate hydration, too much sugar, or stress. If this occurs, slow down, take smaller sips of the gel, walk, and drink plain water. Ensure proper hydration and avoid excess fiber or fat before the race.
Energy Spikes and Crashes: Taking gels too frequently can cause blood sugar fluctuations. Evenly distributed intake helps maintain steady energy. Gels with a mix of sugar types may help with absorption.
Gel Fatigue: If you find it hard to take another gel, switch to an alternative like chews, sports drink, or flat cola.

Conclusion: Practice and Personalize

A frequency of one gel every 30 to 45 minutes after the first hour is a good starting point for most marathoners. However, the most effective approach is a well-practiced and personalized strategy. Train your gut, find your preferred gels and timing, and avoid experimenting on race day. Consistent fueling and hydration are key to a strong marathon performance.

An Outbound Link

For further details on marathon fueling, including high-carb strategies, explore The Running Channel's marathon fueling strategy guide.

Frequently Asked Questions

A first-time marathoner should aim to take their first energy gel around the 60-90 minute mark of the race. This timing ensures that you start replenishing carbohydrate stores before they are significantly depleted, helping to maintain energy levels.

The number of gels you need depends on your finish time and intake rate. For a typical 4-hour marathon, consuming one gel every 30-45 minutes (starting at 60 minutes) would mean carrying between 5 to 7 gels. It's always wise to carry an extra one as a backup.

No, it is not recommended to take two gels at once. Your body can only absorb a limited amount of carbohydrates per hour, and consuming too much at once can overwhelm your digestive system, leading to GI issues and an energy crash.

For most runners, energy gels are not necessary for a 10K run, as your body's glycogen stores are sufficient for exercise lasting under 90 minutes. For runs over 60-90 minutes, such as a half-marathon, gels become beneficial.

Classic gels are concentrated carbohydrates and require water to help with absorption and digestion. Isotonic gels are pre-mixed with water and electrolytes, are thinner in consistency, and can often be taken without extra water, which can be more convenient for some runners.

If you miss a gel, don't try to double up on the next one. Continue with your planned schedule for the next gel. If you're feeling a significant energy drop, take a small amount of an alternative carbohydrate source, like a few sips of a sports drink, to get some quick energy.

Common methods include using a running belt with gel loops, tucking them into pockets on running shorts, or using a hydration vest with front pockets. Practicing with your chosen method during training is important for comfort and accessibility.