Why You Might Experience Nausea After Running—and What to Do to Avoid It

When you run, your body directs oxygen-rich blood away from your stomach to send it to your lungs, heart, and other working muscles. Then, because your stomach doesn’t have its normal resources to digest nutrients efficiently, leaving it feeling queasy as it sends a message that it needs a little help.

This is more likely to happen if you consume too much fuel while running or too soon after you finish. It is also common if you running when it’s hot and humid because your body redirects blood flow to the skin as a means to cool down the body.

To avoid this, practice fueling during training runs to dial in how much fuel your stomach can handle on race day, Carwyn Sharp, Ph.D., exercise physiologist and teaching assistant professor at the University of Denver tells Runner’s World. This is especially important if you’re consuming energy gels or other sugary foods.

It’s important to take notes about what and when you ate. Pay attention to the time from when you ate to when you run to fully understand what works for you and what does not in terms of nutrition, says John Vasudevan, M.D., associate professor of clinical physical medicine and rehabilitation at the University of Pennsylvania and codirector of the Penn Medicine Running and Endurance Sports Program. Remember, too, that race day is not the day to attempt any changes to your fueling routine. If you are someone with a sensitive stomach, avoid grabbing whatever beverages or food are offered on course—even if it’s free, he adds.

“When you run at a high intensity, you increase the pressure in the intra-abdominal space, which puts pressure on your stomach,” Sharp says. This occurs because you use your core more and take heavier breaths while you’re running.

When this happens, it can force contents in your stomach back up into your esophagus—possibly all the way back up to where it started. This scenario is more likely if you had a large quantity of food or liquid in your stomach before a run. This amount is highly individualized, however, so determining what your body can tolerate is essential, especially going into a race.

“The more food you have in your stomach during an intense race or workout, the higher your risk of vomiting,” Sharp says. This is more likely to happen if you suffer from acid reflux or gastroesophageal reflux disease. That’s because the lower esophageal sphincter—the muscles between the esophagus and the stomach—are weakened and may relax when they are not supposed to.

GERD can be treated with medications or an adjustment in diet away from foods that can irritate the esophageal lining, such as acidic foods, tomato products, fatty foods, alcohol, and coffee, Sharp says.

If reflux symptoms become an issue outside of running, such as after walking, it’s probably time to see your doctor, Vasudevan says.

To fuel your runs, focus more on simple carbs rather than high-fat, high-protein, or high-fiber meals and snacks. These foods slow the gastric emptying process. In other words, the food stays in your stomach longer and might give you that “brick in the belly feeling” that’s hard to keep down, making you nauseous.

Also, steer clear of highly acidic foods like citrus fruits (oranges, berries, grapefruits), processed cheeses, as well as liquids like soda or orange juice before your run.

“Acidic foods and beverages cause the stomach environment to be more acidic,” Sharp says, “which slows emptying of the stomach contents into the small intestine, but also increases risk of vomiting.”

One more thing: To keep food-induced vomiting at bay, try not to eat during the two-hour window before a hard workout or race. “If you do need to eat something, make it bland and small in volume,” Sharp says.

Your stomach at rest has a volume similar to that of your fist, so eating an amount equal to that size will help minimize symptoms, Vasudevan notes.

If diet adjustments don’t work, take antacids or Pepto-Bismol about an hour before running to reduce nausea and vomiting.

Hitting the brakes hard after your last interval or once you’ve crossed the finish line can wreak havoc on your stomach because it’s not prepared for the rapid change in exertion, causing you to feel ill as you return to normal. (It’s similar to how you might feel after riding a wild roller coaster.) This can be exacerbated if you really push hard during the final stretch, Sharp says.

Rather than dropping to the curb, keep walking or jogging to give your body time to readjust and ward off stomach cramps.

Also, resist chugging a sports drink or downing food too quickly. Sip on water, keep walking, and allow your body to return to its base level. Take about 30 to 60 seconds between sips to check in with how you feel, Vasudevan adds. If, after 30 to 60 seconds, your mouth still feels dry and your stomach feels fine, take another sip. Hold off a bit if your mouth feels moist or your stomach starts to feel queasy.

William Roberts, M.D., FACSM, chief medical officer of the American College of Sports Medicine, tells Runner’s World that athletes might get nauseated when they sweat a lot. If you lose a significant amount of body weight through sweat while running, your gut quits absorbing liquids correctly, which causes queasiness.

“This is especially true for those who are dehydrated before they start to replace fluids during exercise,” Roberts says.

Dehydration also slows the digestion process even more, so sipping water early and often is important to help you digest food better and help you avoid nausea after running.

“Hydration is key to maintaining a healthy GI after workouts, but it’s a balancing act to hydrate enough to avoid nausea but not too much so as to cause it,” says Sharp.

For those who believe spilling your guts is a sign of a race well run, it’s not. Vomiting can cause damage to the lining of your esophagus, which can affect digestion. It’s important to settle your stomach when you run in order to perform at your best.

Feeling dehydrated or nauseated at the end of a run should prompt you to re-evaluate your hydration strategy both before and during the run, Vasudevan says. Determining the regimen that works for you is just as much a part of training as the distance you cover.