Runners’ Stomach – Causes for Stomach Pain After Running


Do you ever struggle with stomach pain after running? Or perhaps even during running? You’re not alone. Runners’ stomach is a thing, and more than 60 percent of distance runners have been affected at some point!

But even though it’s a real phenomenon, it’s not fun to deal with, either during or after a run. Delving into the potential causes of this kind of pain and discomfort can give you some insight into how to prevent it from happening.

Here are some common causes for stomach pain after running, as well as some quick tips on handling it if it happens to you mid-run.

What Is “Runners’ Stomach?”

Runner’s stomach is a common complaint among runners, where you experience gastrointestinal distress during or after a run. You often have a sudden urge to sprint to the bathroom, with symptoms such as:

  • Painful stomach cramps
  • A grumbling sensation
  • Gas
  • Nausea
  • Vomiting
  • Diarrhea
  • Bloating

Also called runners’ gut or runners’ trots, you do not want it to happen to you when you’re on your way to the finish line!

Common Causes of Stomach Pain After Running

Runners’ stomach can be caused by a variety of factors. In most cases, a combination of these factors leads to pain and other unpleasant symptoms.

Here are some of the most common reasons you could suffer stomach pain after running. Address these, and you may find that your mid-run or post-run gut problems stop!

Reduced Blood Flow in the Gut

One of the most common yet least understood reasons for stomach pain during and after running is reduced blood flow to the gut.

There’s only a limited amount of blood in your body. When you’re exercising, it tends to go more to the heart, lungs, and muscles to facilitate the level of exercise you’re doing. This means it gets diverted away from the organs of your digestive system. Almost 80 percent of blood goes away from the digestive system during exercise.

When there’s less blood flow to the digestive system, digestion slows down and almost stops entirely. This means food in your stomach begins to ferment thanks to gut bacteria. You may experience bloating, gassiness, and cramps because of this.

If you’re quite focused on your run, you may not notice these feelings until after your run when you’ve stopped your activity.

Hormonal Changes

Any exercise counts as stress on the body. When your body is under stress, it releases stress hormones like cortisol and adrenaline. When these hormones are present in the body, you’re in a fight-or-flight state.

This means your blood gets diverted from the stomach so that it’s ready to power your legs if you need to run away from something or your arms if you need to fight. It sounds primitive, but it’s true!

These hormones cause the problem mentioned above—a lack of blood flow to the gut, which can leave you with pain and discomfort after your run.

Incorrect Fueling

Fueling before and after your runs is an important part of success. But doing it incorrectly can lead to stomach pain after running.

Your pre-workout meal—2 to 4 hours before your run—should contain easy-to-digest carbohydrates. It shouldn’t be too high in protein, fat, or fiber, as these can cause GI distress. These compounds take longer to digest, so they can become problematic when the blood flow to the gut decreases.

How you fuel during your run can also make a difference. Some runners dislike the texture of energy gels, which can contribute to a feeling of nausea. However, the biggest key with energy gels and chews is that they need to be balanced out by your water intake.

The sugar in gels and chews can draw water into the gut. This can lead to diarrhea, especially as the gut is jostled as you run. The same is true of energy drinks with high sugar and carbohydrate content.

You can avoid this by practicing your fueling during training. It’s a good way to assess what works for you and doesn’t, so you never have to be caught unawares on race day.

Incorrect Hydration

Dehydration can increase your risk of unpleasant gut symptoms. If you aren’t drinking enough, your body begins to retain water, leading to discomfort.

Interestingly, drinking water with an electrolyte supplement can help. Instead of just taking in plain water—which could unbalance the body’s electrolytes as you lose them through sweat—adding electrolytes to your water can help ease your stomach.

Overhydration is another way you might accidentally end up with gut problems. Too much water means you’re at risk of cramps and diarrhea, so it’s essential to figure out what’s right for you during training.

Pre-Workout Supplements & Vitamins

If you take pre-workout supplements, some can inadvertently cause gastrointestinal distress. In particular, those with high levels of caffeine can cause cramping and diarrhea.

Usually, the body needs some time to adjust to these supplements, so you should be able to continue using them.

How to Prevent Runners’ Stomach

Wondering how to prevent stomach pain after a run? Here’s some good advice.

Strengthen Your Gut

Taking a probiotic supplement can help to boost the good bacteria in the gut, help it to absorb nutrients, and help you to strengthen your gut and make it more resilient against potential threats.

Studies indicate that probiotics can help to reduce the chance of GI distress during a race. It’s best to discuss this with your doctor first, as they’ll be able to give you the right probiotic strains and the right dosage.

Experiment With Fueling

It may take some time to optimize your fueling. You’ll need to experiment both with pre-workout fueling—whole food and supplements—and mid-run fueling to find out what works best for you.

During training, try different pre-workout meals and see how you feel running after each one. Make sure whatever you try is healthy, high-carb—about 15 to 20 grams to start, up to 60 grams depending on you—and low in protein and fats.

On the other hand, you could try running fasted—without a pre-workout meal—with just a pre-workout supplement. You’ll need to try a few different pre-workouts to see which gives you the boost you need. Some people will tolerate caffeine well, while others won’t, for example.

You’ll also need to play around with your mid-run fueling. Some runners may not be able to tolerate the consistency of energy gels, but it might also just be a case of finding the right brand for you.

Clean Up Your Diet

Pre-workout isn’t the only meal you need to be careful with. If you often suffer from stomach pain after running, you might benefit from shifting to a low-sugar, low-carbohydrate diet. A low-FODMAP diet may be the way to go for many.

How to Handle Stomach Pain During a Race

What happens when you feel the telltale signs of runners’ stomach during a race? Here are some things you can do to ease the pain and prevent it from becoming worse.

Slow Down

The faster you run, the more your stomach gets jostled around. Slowing down gives your body some space to allow for blood to flow back to the stomach and to settle whatever is in your stomach at the time.

Sip Water Slowly

Don’t gulp your water down, as this could worsen pain and discomfort. Sip water slowly to prevent dehydration. If you can, try to find cold water instead of warm water heated by the sun. Warm water could speed up the digestive process, having you running for the bathroom!

Eat A Bland Snack

You might also suffer from abdominal issues during a race if your stomach is empty. If you didn’t fuel up before your race, try to eat a bland snack during the race, like some crackers or a granola bar.

Try Ginger

Ginger is excellent for sore stomachs or nausea. Add a ginger sweetener or two to your stash if you’re already carrying energy gels or chews in your pockets.

When you start to feel nauseous, suck on the ginger. It helps to dampen nausea, but it will not necessarily fix the problem. You should still sip a bit of water, slow down, and try to snack on something bland.

Take a Pit Stop

When all else fails, you may need to make a stop along the way. There’s no shame in this—it even happens to the greats! Make sure you know where the closest toilets are.

When to Worry About Runner’s Stomach

If you suffer from runners’ stomach occasionally, it’s quite normal. Sometimes small changes in diet, not getting enough sleep the night before, or the beginnings of a cold can lead to digestive upset.

But when it happens often—or every time you run—you should visit your doctor to ensure there’s no underlying reason for it.

If you experience any of the following symptoms along with runners’ stomach, you should stop immediately and seek medical attention:

  • A headache
  • Lightheadedness
  • Dizziness
  • Vomiting
  • A lack of sweating

You should also get it checked by a doctor if you have the symptoms of runners’ stomach even when you don’t run.

Photo of author


Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.