Marathon Gels: What They Are, How They Work, and Which Ones Runners Really Use

When you hit mile 18 of a marathon and your legs feel like lead, marathon gels, concentrated carbohydrate packets designed to quickly replenish energy during endurance events. Also known as energy gels, they’re not magic—but they’re close. Most runners don’t just drink water—they carry these little packets like lifelines. They’re small, easy to stash in a pocket or waist belt, and deliver a fast spike of glucose when your body’s glycogen stores are empty.

Marathon gels work because your body runs on sugar—specifically, stored glycogen. After about 90 minutes of running, that supply starts to run dry. That’s when you crash, or "hit the wall." A gel gives you 20–30 grams of carbs, mostly from maltodextrin and fructose, which your body absorbs fast. Some even include caffeine, sodium, or amino acids to delay fatigue or reduce cramping. But they’re not all the same. Some taste like syrupy chalk. Others go down smooth. And timing matters: most runners take one every 45 to 60 minutes, starting around mile 6. Too early, and you waste it. Too late, and you’re already fading.

It’s not just about the gel—it’s about how you use it. You need to train with them, not just on race day. If you’ve never tried one before a long run, you might end up with stomach cramps or nausea. That’s because your gut needs to adapt to processing concentrated sugar while you’re pounding the pavement. Many runners pair gels with water, not sports drinks, to avoid too much sugar at once. And don’t forget: if you’re running in cold weather, gels can freeze. Keep them in an inner pocket, close to your body.

There’s a whole world of brands out there—Gu, Maurten, Science in Sport, Clif—each with different formulas, textures, and flavors. Some use real fruit. Others rely on synthetic sugars. Some come in squeezable packets. Others are thicker, almost like paste. The best one? The one you’ve tested and know your stomach tolerates. No pro runner wins with a new gel on race day.

Marathon gels are part of a bigger picture: running nutrition, the science of fueling your body before, during, and after long-distance runs. It’s not just about eating more carbs—it’s about timing, digestion, and personal tolerance. Your pre-race meal, hydration plan, and gel strategy all connect. Skip one, and you might pay for it at mile 22.

And while gels get all the attention, they’re not the only option. Some runners use chews, dates, or even mashed banana. But gels are the standard for a reason: they’re precise, portable, and proven. They’re the tool that turns a slow, painful grind into a steady, controlled effort.

Below, you’ll find real advice from runners who’ve been there—how to pick the right gel, when to take it, what to avoid, and how to make it work for you, no matter your pace. Whether you’re aiming for a 4.5-hour finish or just trying to get to the line without walking, this collection has what you need to keep going.