Ethan BrooksBy Ethan Brooks

Updated November 2026

Yes, energy gels can cause diarrhea, especially during long runs or races. The most common triggers are high carbohydrate loads taken too quickly, concentrated sugars that draw water into the gut, and gels taken without enough water. Gut tolerance varies widely, so what upsets one runner may sit fine with another.

Why Energy Gels Can Upset Your Stomach

Energy gels are designed to deliver fast-absorbing carbohydrate, usually 20 to 30 grams per packet, in a small, concentrated volume. That concentration is what makes them useful, and it is also what causes problems. When a large amount of sugar reaches the small intestine faster than the body can absorb it, the excess pulls water in by osmosis. The result can be cramping, bloating, urgency and loose stools.

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

Exercise adds another layer. Blood flow shifts away from the digestive tract toward working muscles and skin, which slows digestion and makes the gut more sensitive to whatever is in it. A gel that sits comfortably at rest can feel very different at kilometer 25.

Factors That Increase the Risk

Several variables determine whether a gel causes diarrhea:

  • Carbohydrate type and concentration. Gels high in fructose or in multiple sugars can be harder to absorb in large amounts than maltodextrin alone. Many gels use a blend specifically to improve absorption, but a high total intake still strains the gut.
  • Intake rate. Taking two or three gels in a short window is a common mistake. Spacing them out matters more than the gel itself.
  • Fluid intake. Gels are concentrated. Without enough water, osmotic load becomes a bigger problem.
  • Intensity. Hard efforts divert blood away from the gut more than easy running does.
  • Additives. Some gels contain caffeine, electrolytes or sweeteners that can irritate sensitive stomachs. Check the label for sugar alcohols such as sorbitol, which are a well-known laxative.
  • Individual sensitivity. Some runners have sensitive guts, a history of irritable bowel symptoms or simply a low tolerance for fructose.
  • Heat and dehydration. Hot conditions increase the chance of gut distress, particularly when fluid losses are not replaced.

Most gut problems from gels can be reduced with a systematic approach. Treat gut training like any other part of your training plan.

  1. Start testing gels on training runs, not on race day. Try the exact product, flavor and timing you plan to use.
  2. Begin with a lower intake, for example one gel per hour, and increase gradually over several weeks.
  3. Take each gel with about 150 to 250 milliliters of water, and sip regularly rather than gulping.
  4. Check ingredient labels for sugar alcohols, high-fiber additives and high caffeine doses if you are sensitive.
  5. Consider switching brands. A different carbohydrate blend or a lower-concentration gel may sit better.
  6. Avoid new gels in the 24 hours before a key workout or race, and avoid stacking gels with other sugary foods.
  7. Keep a log of intake, pace, weather and symptoms. Patterns often show up within a few long runs.

If diarrhea is severe, bloody, persistent, or accompanied by fever or dehydration, stop fueling with gels and see a doctor. Runners with a diagnosed digestive condition should consult a sports dietitian or physician before changing their fueling strategy.

Practical Tips for Race Day

  • Plan your gel schedule on paper before the race, including kilometer or mile markers and water stations.
  • Carry only gels you have used successfully in training.
  • If you feel gut discomfort mid-race, slow down, sip water and skip the next gel for a while.
  • Consider a mix of gels and solid foods, such as chews or bananas, to spread the carbohydrate load.

What We’d Use

Gels with a multiple-carbohydrate blend and no added sugar alcohols tend to be a reasonable starting point for runners with sensitive stomachs. Look for a formula you can test in training. View on Amazon

Runners who want to reduce concentration can try a lower-sugar gel, paired with extra water on the run. View on Amazon

Can energy gels cause diarrhea even if I have no stomach problems?

Yes. Even runners with strong guts can react to high intake, low fluid or hard efforts. Tolerance is situational.

How long after taking a gel does diarrhea usually start?

Symptoms often appear within 30 to 90 minutes, depending on intensity, fluid intake and the gel’s composition.

Are caffeine gels more likely to cause diarrhea?

Caffeine can stimulate bowel movements in some people, so caffeinated gels may be a trigger for runners who already have a sensitive gut.

Should I stop using energy gels if they upset my stomach?

Not necessarily. Try adjusting timing, water intake and brand first. If problems persist, consider solid carbohydrate sources or consult a sports dietitian.

Can I train my gut to tolerate gels better?

Yes. Gradually increasing intake during long training runs over several weeks can improve tolerance for many athletes.

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.