Ethan BrooksBy Ethan Brooks

Updated November 2026

If energy gels give you diarrhea, the most common cause is the way your gut handles concentrated sugar while you are running. Gels pack a lot of carbohydrate into a small volume, and when that load outpaces your intestines’ ability to absorb it, the extra sugar and water pull into the bowel. Changing the gel type, timing and fluid intake usually fixes the problem.

Why Gels Can Upset Your Gut

Running diverts blood flow away from the digestive tract toward working muscles and skin. That slows digestion and reduces absorption, so anything you swallow sits in the gut longer than it would at rest. Add a concentrated carbohydrate and the osmotic effect can draw water into the intestine, which speeds things up in the wrong direction.

Shopping for one? See our guide: Honey Stinger Energy Gels Review (2026): Pros and Cons.

Many gels also contain fructose or sugar alcohols, which some people absorb poorly. Unabsorbed sugar ferments in the colon and produces gas and loose stool. For a fuller breakdown of the mechanisms, see our guide on Can Energy Gels Cause Diarrhea? Causes and How to Prevent It.

Factors That Make It Worse

Several variables tend to stack up on race day:

  • Gel type. Gels high in fructose or containing sugar alcohols are more likely to cause trouble. Check the label before you buy a box.
  • Carbohydrate per hour. Taking more than about 60 grams of carbohydrate an hour is hard for most runners to absorb without GI symptoms, and single-source glucose gels tolerate better at higher doses than mixed sources.
  • Fluid. Taking a gel with very little water can make the sugar load more concentrated in the stomach. Sipping water with each gel helps dilute it.
  • Intensity. Hard efforts shift blood away from the gut more than easy running does, so a gel that is fine at an easy pace may cause problems at race pace.

Maltodextrin is a common carbohydrate in gels, and it has its own trade-offs; Why Is There Maltodextrin in Energy Gels? Purpose and Trade-Offs explains why manufacturers use it.

What to Do About It

Treat your gut like any other part of your training. Test your fueling on long runs before race day, and change one variable at a time so you can tell what helps.

  1. Start with a lower dose, around 20 to 30 grams of carbohydrate per hour, and build up over several weeks.
  2. Switch to a gel with a glucose-dominant carbohydrate blend if fructose is the suspected trigger.
  3. Take each gel with 4 to 6 ounces of water, and avoid large gulps of plain water right after.
  4. Take gels early and at regular intervals, such as every 30 to 45 minutes, rather than all at once when you feel low.
  5. Practice the same plan in race-like conditions, including heat and your race-day pace.

For timing guidance tailored to distance, see When to Use Energy Gels Running: Timing, Dosing and Race-Day Tips.

What We’d Use

If you need a gel that is generally gentler on the stomach, look for a glucose-based formula with a clear ingredient list and no added sugar alcohols. Products like the Maurten Gel 100 are often discussed among runners with sensitive stomachs, though individual tolerance varies. View on Amazon

Many runners also prefer a multi-carb gel designed for steady absorption over long efforts, such as the GU Roctane Energy Gel, which is widely used in endurance events. View on Amazon

FAQ

Can I still use gels if they upset my stomach?

Often yes, once you adjust the type, dose and fluid intake. Test changes on training runs rather than on race day.

For most runners it passes within a few hours after the run ends. Persistent or severe symptoms should be checked by a doctor or sports dietitian.

Should I stop taking gels altogether?

Not necessarily. Many runners switch to chews, drink mixes or real food such as dates or rice cakes. A registered dietitian can help you build a plan that fits your body.

Ready to choose one?

Ethan Brooks

About Ethan Brooks

Ethan Brooks is part of our editorial team and reviews and edits our marathon & half-marathon guides, checking product details against manufacturer specifications and owner feedback.