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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Runner’s diarrhea is frequent, loose stool during or shortly after a run. Running can contribute through physical jostling, changes in blood flow and digestion, food and drink choices, and pre-run stress—but no single cause explains every case. Track your own pattern and test modest changes; see a doctor for blood in your stool, persistent symptoms, or diarrhea that does not improve.
Why do you get diarrhea when you run?
Runner’s diarrhea is most often reported by long-distance runners, but it can happen during or immediately after other runs too. Exercise-related symptoms may reflect several factors acting together rather than one identifiable trigger.
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- Reduced blood flow to the gut: During strenuous exercise, blood flow may shift away from the digestive system. Hypohydration can contribute to reduced mesenteric blood flow.
- Running’s physical impact: Repeated jostling may aggravate the digestive tract.
- Changes in digestion: Exercise can affect intestinal hormone secretion and gut activity.
- Food and drink: Unfamiliar or increased food intake, and some ingredients in drinks or energy products, may contribute.
- Stress or anxiety: Pre-race nerves may play a role for some runners.
These are possible contributors, not a diagnosis of what is happening in an individual case. Gastrointestinal complaints are common across sport: a 2014 review estimated that 30–50% of athletes report GI complaints in studies generally. That figure is not a rate for runner’s diarrhea specifically, and estimates vary by study methods, population, sport, intensity, and conditions. The review in Sports Medicine discusses those differences.
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How to find your triggers without over-restricting food
There is no established forbidden-food list or prevention routine that works for every runner. Instead, keep a short diary for several runs and look for a pattern.
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- Record the run’s duration and intensity, and when symptoms begin.
- Note what and when you ate, including fiber-rich or high-fat foods.
- Record caffeine, gels, bars, sports drinks, and other products.
- Note hydration, pre-run stress, and whether the run or food was unusual for you.
Change one plausible factor at a time where practical. A change is more useful if it reduces symptoms while still allowing you to eat and drink adequately. If symptoms keep recurring, a clinician or sports dietitian can help assess the pattern.
Changes to test before a run
Mayo Clinic suggests several adjustments that runners can test against their own symptoms. They are options, not mandatory restrictions for everyone.
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- Experiment with an amount and timing of fiber you tolerate; consider limiting high-fiber or gas-producing foods shortly before a run if your diary points to them.
- Avoid sugar alcohols before running if they appear to trigger symptoms.
- Try limiting caffeine and high-fat foods in the hours before a run if they correlate with urgency or loose stool.
- Consider avoiding food for a short period before running if eating close to a run is a repeatable trigger.
- Drink fluids, and be cautious with energy gels and bars. Do not try a new product on race day.
- Avoid using NSAIDs such as ibuprofen or naproxen to manage a run unless a clinician advises you; they can increase gastrointestinal complaints. If you take regular medication, discuss any change with your clinician.
Mayo Clinic’s advice is to consult a health care provider if practical changes do not help. Its prevention guidance was published July 8, 2021.
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Specific prevention strategies are not equally well established. A 2017 review describes ischemic, mechanical, and nutritional factors as major proposed causes, while noting that research supporting prevention strategies is limited. It does not support recommending a gluten-free diet to prevent exercise-induced diarrhea in athletes who do not have celiac disease. Read the review abstract.
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A 2025 joint position statement supports individualized assessment and identifies hydration, carbohydrate and protein intake, dietary FODMAP manipulation, and gut training or adjustments to feeding tolerance among strategies with generally consistent beneficial outcomes for exercise-associated symptoms. That does not establish a single dose or schedule for every runner, nor does it mean everyone should follow a restrictive low-FODMAP diet. Discuss substantial dietary changes with an appropriately qualified professional. The 2025 position statement emphasizes choosing management based on an individual’s symptoms and contributing factors.
When should you see a doctor?
Contact a health care provider if you see blood in your stool, have persistent diarrhea, or symptoms continue despite reasonable changes. The International Foundation for Gastrointestinal Disorders advises bringing bleeding and persistent diarrhea to a doctor’s attention and discussing athlete diarrhea with a health care provider. Its patient guidance discusses exercise-related GI symptoms.
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If symptoms are severe or you feel acutely unwell, seek prompt professional assessment instead of assuming the cause is running or trying to manage it on your own. These warning points are not a complete diagnostic checklist; a clinician can assess whether another cause needs attention.
Should you take medicine or buy a special product?
No medication, food schedule, gel, or hydration device is established as a universal fix for runner’s diarrhea. Because symptoms and possible triggers differ, do not make antidiarrheal medicine a routine solution without individualized advice from a health care professional. A diary and a targeted, low-risk adjustment are more useful starting points than buying a product or eliminating broad food groups.
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- HEALTHY & CONVENIENT HYDRATION: Include 2x 10oz/300ml NO RESIDUAL TASTE BPA-free Water Bottles, which apart from safe is also incredibly durable, You don't need to remove the cap in order to drink your water, this drinking bottle has a leakproof PUSH-PULL nozzle that allows you to enjoy your water even while you're on the move! TOP TIP, wash the flask out a few times before using.
- SPATIAL DESIGN AND SPORTS PROFESSIONAL: The bottle running belt is perfect for credit cards, ID, keys, paper towel, bars choc, energy gel packs, running accessories, etc, very convenient. Convenient 6.5 Inches Large Pocket fits most smartphone phones up to 6.5 inches, like iPhone 8 Plus, 7S Plus, 6 Plus.
- SUPER EASY TO WEAR & SAFE: Complete with headphone hole, enjoy the music during running. Design of 2 removable race bib strap toggles can hold your race number for triathlons, marathons or running race. Reflective tab on the pocket ensures your safety in the night runs. Ideal for endurance running & training. Also suitable for walking, dog walking, hiking, golf, skateboarding, snowboarding and cycling.
- PEACE OF MIND AFTER SALES SERVICE - We, AiRunTech Team, provide lifetime after sales service for you unconditionally on all the products to make sure that customers enjoy to buy our products.
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