Do Side Stitches Mean You're Dehydrated? What the Research Actually Says

No — current research doesn't support dehydration as a cause of exercise-related side stitches, and the fix most runners reach for instinctively, chugging water right before heading out, is actually the thing more likely to bring one on.

What's Actually Happening When Your Side Cramps Up

The sharp pain under the ribs that shows up during running, swimming, or other rhythmic exercise is technically called exercise-related transient abdominal pain, and the leading explanation involves the parietal peritoneum, a thin tissue lining the abdominal wall and diaphragm. Researchers studying the condition believe repetitive torso movement, combined with a full stomach pulling on that lining, irritates it enough to cause the sharp, localized pain athletes describe. It's a mechanical and digestive issue, not a hydration one — which is why it tends to show up regardless of how well-trained or well-hydrated someone generally is.

Why Drinking Water Isn't the Cause — But Drinking a Lot of It Right Before Exercise Can Be

This is the distinction that gets lost: being hydrated doesn't cause a side stitch, but drinking a large volume of fluid, especially something sugary, in the minutes right before a run increases the odds of one. A full stomach is more likely to pull on the diaphragm lining during the up-and-down motion of running, whether that fullness comes from food or from a quart of water gulped at the start line. The fix isn't avoiding water — it's timing it, the same way athletes are told to avoid a heavy meal right before a workout.

The Timing Fix That Actually Works

Spreading fluid intake across the day, in smaller amounts, keeps a runner just as hydrated at the start of a workout without the stomach fullness that a single large pre-run gulp creates. Practically, that means treating water the way most people already treat food before exercise: steady intake earlier in the day, a modest amount in the 30 to 60 minutes beforehand, and sips rather than large gulps once moving, instead of one big bottle finished at the trailhead.

What Else Plays a Role

Posture and breathing pattern matter too — shallow, rapid breathing during exercise has been associated with a higher likelihood of side stitches than slower, deeper breathing, and some research points to poor posture compressing or irritating nerves near the ribs as a contributing factor. None of this points back to being under-hydrated; if anything, it reinforces that a side stitch is a mechanical and digestive event layered on top of exercise, not a warning sign that more water is needed in the moment.

When It's Worth a Closer Look

An ordinary side stitch usually eases within minutes once you slow down, breathe deeper, or press on the area. Sharp chest or upper-abdominal pain that doesn't resolve with rest, or that comes with shortness of breath, dizziness, or pain radiating to the arm or jaw, is not a side stitch and warrants prompt medical attention rather than a pace change.

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This article is for general informational purposes only and is not medical advice. Chest or upper-abdominal pain that doesn't ease with rest, or that comes with shortness of breath, dizziness, or pain spreading to the arm or jaw, needs prompt medical evaluation rather than home management.

Sources: GoodRx Health, "What Causes Side Stitches, and How Can You Prevent Them?" • goodrx.com/conditions/musculoskeletal/what-causes-side-stitches • Morton, D.P. and colleagues, research on exercise-related transient abdominal pain (ETAP), as summarized in peer-reviewed sports-medicine literature • National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intakes for Water