How Often Should I Eat GU During a Marathon?

December 11, 2025 •

4 min read

According to GU Energy, runners should consume one energy gel 5 minutes before and then every 45 minutes during endurance exercise to maintain energy levels. Understanding how often should I eat GU during a marathon is crucial for proper fuel management, preventing fatigue, and achieving your best performance on race day.

Quick Summary

This guide provides an in-depth fueling strategy for marathon runners using GU gels, explaining optimal timing, frequency, and quantity based on individual needs and race conditions. It details how to train your gut, manage hydration, and customize your nutrition plan to maximize performance and avoid gastrointestinal issues during a race.

Key Points

Standard Recommendation: Consume one GU gel 5 minutes before the race and another every 45 minutes during the marathon.
Adjust Frequency: Faster runners or those targeting higher carbohydrate intake might fuel every 20-30 minutes, while slower runners can extend intervals to 60 minutes.
Always Use Water: Consume a few sips of water with each gel to aid digestion and prevent stomach discomfort and dehydration.
Train Your Gut: Practice your exact race-day fueling and hydration strategy during long training runs to ensure your stomach is prepared.
Consider ROCTANE: For longer races or high-intensity efforts, GU ROCTANE gels offer additional amino acids and electrolytes.
Customization is Key: Your optimal fueling plan depends on your individual pace, weight, and tolerance, so experiment with timing and frequency.
Manage Caffeine: Use caffeinated gels strategically during the race, or opt for caffeine-free versions, as excessive caffeine can cause jitters or stomach issues.

Your Marathon Fueling Strategy with GU Gels

Proper fueling is a cornerstone of marathon success, and for many runners, GU energy gels are a go-to source for quick, easy-to-digest carbohydrates. While the manufacturer provides general guidelines, an optimal fueling strategy is highly personal and depends on your pace, training, and gut tolerance. Your body’s glycogen stores can sustain moderate-to-high-intensity running for roughly 90 minutes before depletion, which is why supplementing with external carbohydrates is vital for any effort lasting longer than an hour.

The Standard GU Recommendation

GU Energy Labs officially recommends a simple and effective fueling schedule: take one gel 5 minutes before starting and then one gel every 45 minutes during your run. Each GU gel contains a blend of carbohydrates, including maltodextrin and fructose, designed for efficient absorption into the bloodstream. This dual-carbohydrate approach helps your body process more fuel per hour than a single source and provides a steady energy stream to prevent a sudden sugar crash.

Customizing Your Fueling Frequency

For many runners, the standard 45-minute interval is a solid starting point, but personalizing your intake can lead to better results and fewer GI problems. Faster runners or those who can tolerate more carbohydrates might benefit from more frequent fueling. Elite runners often target a higher carb intake, sometimes as much as 60-90 grams per hour, which would necessitate consuming a gel every 20-30 minutes. Conversely, newer or slower runners may find that a gel every 45-60 minutes is sufficient. The key is to experiment during your long training runs to find what your stomach can handle comfortably at race pace.

Example Marathon Fueling Schedules

Beginner (4+ hours): Take your first gel 5 minutes before the start, then take another every 45 minutes. This would equate to one gel at the start and gels at approximately miles 3, 7.5, 11.5, 15.5, 19.5, and 23.5, assuming an average 10-minute mile pace. Always take with water.
Intermediate (3-4 hours): After the initial gel, consume a gel every 30-40 minutes. This could mean one at the start, and then every 3 miles or so, such as at miles 3, 6, 9, 12, 15, 18, 21, and 24. For a 4-hour race, this is 8-12 gels total.
Advanced (Sub-3 hours): Aim for a higher carbohydrate intake, potentially 60-90g per hour, and a gel every 20-30 minutes. This might mean one gel at the start, and then every 2-3 miles. Practice this intensity and frequency during your longest training runs.

The Critical Role of Hydration

Taking a gel is only half the equation; proper hydration is essential for digestion and absorption. Without water, the concentrated sugars in the gel can pull water from your digestive tract, potentially causing stomach cramps and dehydration. A good rule of thumb is to take a few sips of water with every gel. Be aware of race-day hydration stations, but also consider carrying your own water in a handheld bottle or hydration pack, especially if you plan to use a different sports drink than what is provided.

Training Your Gut for Race Day

Your digestive system needs training just like your legs. You should never try a new gel or fueling strategy on race day. During your long training runs, practice the exact fueling schedule you intend to use in the marathon. This includes the timing, frequency, specific GU gel flavors (some have caffeine, others don't), and the type of fluid you'll use to wash them down. Keeping a training log can help you track how different fueling intervals and products affect your energy levels and stomach. This is also the time to test if you want to incorporate caffeinated gels strategically.

Alternative Fuels and the Benefits of ROCTANE

While GU Original gels are a standard for a reason, GU also offers ROCTANE gels, which are designed for longer efforts. ROCTANE gels contain more amino acids and electrolytes, which can help reduce muscle damage and support heart function during prolonged activity. Mixing up your fuel sources can also be helpful. Some runners combat flavor fatigue by alternating between gels, chews, and sports drinks. Others find a mix of solid food and gels works best for them.


Feature	GU Original Energy Gel	GU ROCTANE Energy Gel
Primary Use	Standard endurance fuel	High-intensity or prolonged efforts (>90 min)
Carbohydrates	Maltodextrin & Fructose	Maltodextrin & Fructose
Amino Acids	Standard amounts	Extra Branch Chain Amino Acids (BCAAs)
Electrolytes	Sodium, typically 50-125mg	More sodium than Original
Caffeine Options	Some flavors available	Some flavors available
Overall	Reliable energy for most runs	Enhanced formula for tougher conditions

A Final Fueling Checklist

Carb-Load Properly: In the 2-3 days leading up to the marathon, increase your carbohydrate intake to top off glycogen stores.
Pre-Race Meal: Eat your final meal 2-4 hours before the race. Make it carb-heavy and low in fiber.
Take a Pre-Race Gel: Take your first GU gel about 5-15 minutes before the start.
Practice on Long Runs: Test your gel timing and flavor preferences during long training runs to train your stomach.
Use Water: Always drink a few sips of water with each gel to aid absorption and prevent stomach upset.
Listen to Your Body: Pay attention to your energy levels. If you feel a dip, take a gel earlier. If you feel nauseous, space them out more or switch flavors.
Have a Backup Plan: Carry an extra gel just in case.

Conclusion

Mastering your marathon fueling strategy is a game-changer. By understanding the standard recommendation to eat GU gels every 45 minutes and then customizing that frequency based on your individual needs and pace, you can ensure a steady supply of energy throughout the race. Don't forget the vital combination of gels with water and the importance of practicing this nutrition plan during training to avoid race-day surprises. With a well-thought-out fueling plan, you'll be able to conquer the marathon distance and cross the finish line strong.

Frequently Asked Questions

The standard recommendation is to take one GU gel 5 minutes before your race and then one gel every 45 minutes during the marathon. Many runners adjust this based on their pace and tolerance, with some fueling every 20-30 minutes for higher intensity.

Yes, unless you are using a specifically formulated isotonic gel, it is critical to drink a few sips of water with each GU gel. This helps your body properly digest and absorb the concentrated carbohydrates and prevents stomach upset.

Practice during your long training runs and track your energy levels in a log. If you feel a noticeable energy crash or 'bonk' near the end of a long run, you may need to increase the frequency or quantity of your gels. A good benchmark is to aim for 30-90 grams of carbohydrates per hour.

Yes, you can use caffeinated GU gels, but use them strategically. Some runners take a caffeinated gel in the later stages of a race for a mental boost. However, practice with them first, as they can cause jitters or GI issues in sensitive individuals.

Gastrointestinal distress is a common issue. Try practicing with gels during training to let your gut adapt, use smaller amounts more frequently, or switch to a less-processed brand or alternative fuel. Pairing with water is also crucial.

It is best to take your first GU gel about 5-15 minutes before the start of the race to top off your glycogen stores and begin fueling proactively.

GU ROCTANE gels are formulated for longer, more intense efforts, providing additional amino acids and electrolytes compared to the Original gels. The best choice depends on your specific race strategy and body, but ROCTANE is often preferred for marathons due to its enhanced formula.