Quick answer
- Most abdominal pain while running is one of three things.
- A side stitch, properly called exercise-related transient abdominal pain, is a sharp pain under the ribs caused by irritation of the membranes lining the abdominal cavity; it is strongly linked to drinking large volumes of concentrated fluid shortly before or during running.
- A true stomach cramp with nausea or bloating is usually food that has not left the stomach, often because it was high in fat, fibre, or protein, or eaten too close to the run.
- Lower abdominal cramping with urgency is runner’s stomach, driven by reduced gut blood flow and mechanical jostling at higher intensities.
- The fixes differ, but all three respond to earlier and simpler eating, diluted drinks, and progressive gut training.
5 key facts
- Side stitches affect around two-thirds of runners in a given year and are most common in less-trained runners and after drinking hypertonic fluids.
- Blood flow to the gut falls sharply during hard exercise, which is why symptoms scale with intensity rather than distance.
- Drinks above roughly 8 percent carbohydrate concentration empty from the stomach slowly and are a frequent cause of mid-run cramping.
- A low-FODMAP day before hard sessions has been shown to reduce gastrointestinal symptoms in runners prone to them.
- The gut is trainable: repeated practice of race-day fuelling in training measurably improves tolerance.
Abdominal pain is the most common reason runners abandon a session, and it is also the one most often blamed on the wrong thing. "I got a stitch" covers at least three separate problems with different causes and different fixes, and treating them as one is why the same runner keeps getting the same pain for years.
So the first job is diagnosis. Where does it hurt, what does it feel like, and when did it start relative to what you ate and drank?
Which one do you have?
Sharp, localised pain under the ribs, often on the right, worse on hard breathing
Most likely causeSide stitch (exercise-related transient abdominal pain)
Typical triggerDrinking a large volume of concentrated fluid before or during the run
Dull upper cramp with fullness, nausea, or burping
Most likely causeFood still in the stomach
Typical triggerA meal eaten too recently, or too high in fat, fibre, or protein
Lower abdominal cramping with urgency or looseness
Most likely causeRunner’s stomach, lower-GI symptoms
Typical triggerReduced gut blood flow at high intensity, plus fibre or FODMAPs from the previous day
Burning behind the breastbone, sour taste
Most likely causeReflux
Typical triggerEating too close to the run, or a very acidic drink
Cramp that arrives late in long runs alongside muscle cramping
Most likely causeFluid and sodium imbalance, or simply fatigue
Typical triggerVery high sweat losses, or a hypertonic drink taken repeatedly
| Symptom pattern | Most likely cause | Typical trigger |
|---|---|---|
| Sharp, localised pain under the ribs, often on the right, worse on hard breathing | Side stitch (exercise-related transient abdominal pain) | Drinking a large volume of concentrated fluid before or during the run |
| Dull upper cramp with fullness, nausea, or burping | Food still in the stomach | A meal eaten too recently, or too high in fat, fibre, or protein |
| Lower abdominal cramping with urgency or looseness | Runner’s stomach, lower-GI symptoms | Reduced gut blood flow at high intensity, plus fibre or FODMAPs from the previous day |
| Burning behind the breastbone, sour taste | Reflux | Eating too close to the run, or a very acidic drink |
| Cramp that arrives late in long runs alongside muscle cramping | Fluid and sodium imbalance, or simply fatigue | Very high sweat losses, or a hypertonic drink taken repeatedly |
One warning before the fixes. Everything here concerns exercise-related pain that starts during running and settles afterwards. Abdominal pain that persists at rest, wakes you at night, comes with blood in the stool, unexplained weight loss, fever, or vomiting is not a running problem and needs a doctor rather than a nutrition change.
The side stitch, explained properly
The old story about the diaphragm cramping has largely been abandoned. The best current explanation is irritation of the parietal peritoneum, the membrane lining the abdominal wall, which is richly supplied with nerves and produces exactly the sharp, well-localised pain runners describe. Friction between that membrane and the visceral layer covering the organs increases when the stomach is distended, which is why the strongest single association is with drinking large volumes shortly before or during a run, and why concentrated drinks are worse than water.
Surveys find that around two-thirds of runners experience a stitch at least once a year, that it becomes less common as training experience increases, and that it is more common in younger runners. It is also more common in sports involving repetitive torso movement, which is a hint about the mechanical component.
- Immediate fix: slow down, then breathe deeply into the belly rather than the upper chest. Deep, slow breaths reduce the pain far more reliably than the folk remedy of holding your breath.
- Press firmly into the painful area with your fingers while exhaling. It sounds crude and it usually works.
- Change which foot strikes the ground as you exhale. Many runners consistently exhale on the same foot; switching alters the mechanical loading on the affected side.
- Stretch the side by raising the arm on the painful side overhead and leaning gently away as you jog easy.
- Prevent it next time: stop drinking large volumes in the 30 minutes before a run, dilute concentrated drinks, and strengthen your core and deep trunk muscles.
Fixing cramps caused by food
If your cramp comes with fullness, sloshing, or nausea, the problem is almost always that your stomach still has work to do. Gastric emptying slows as intensity rises, and it slows further with fat, fibre, and protein. A meal that would be entirely comfortable on the sofa can become a rock at threshold pace.
3 to 4 hours
Safe to eatA normal mixed meal
AvoidVery large portions, heavy fried food
2 to 3 hours
Safe to eatCarbohydrate-forward meal, low fat and fibre
AvoidCreamy sauces, large amounts of meat, big salads
1 to 2 hours
Safe to eatSmall carbohydrate snack: toast and jam, banana, white rice
AvoidNuts, nut butter, beans, high-fibre cereal, dairy if you are sensitive
30 to 60 minutes
Safe to eatA gel, a few dates, a sports drink
AvoidAnything solid and bulky
Under 30 minutes
Safe to eatFluid only, small sips
AvoidEverything else
| Time before running | Safe to eat | Avoid |
|---|---|---|
| 3 to 4 hours | A normal mixed meal | Very large portions, heavy fried food |
| 2 to 3 hours | Carbohydrate-forward meal, low fat and fibre | Creamy sauces, large amounts of meat, big salads |
| 1 to 2 hours | Small carbohydrate snack: toast and jam, banana, white rice | Nuts, nut butter, beans, high-fibre cereal, dairy if you are sensitive |
| 30 to 60 minutes | A gel, a few dates, a sports drink | Anything solid and bulky |
| Under 30 minutes | Fluid only, small sips | Everything else |
Two specific offenders deserve naming. Sugar alcohols such as sorbitol and xylitol, common in sugar-free bars, sweets, and chewing gum, are poorly absorbed and reliably cause bloating and cramping during exercise. And large fructose doses without accompanying glucose overwhelm the single intestinal transporter that carries fructose, leaving unabsorbed sugar drawing water into the gut. That is why modern sports products use a glucose-to-fructose blend rather than fructose alone.
If a product keeps upsetting you, swap it for a lower-risk version before you give up on fuelling altogether.
Gels heavy in fructose without matching glucose
Gels led by glucose or maltodextrin, or a glucose-fructose blend you have practised with
Whole fruit during the run
Gels or chews made for sport
Juice or soda at full strength
A 6 to 8 percent sports drink
High-fibre energy bars
Low-fibre chews or blocks
Dairy-based products, if you are sensitive
Dairy-free versions
| Higher GI risk | Lower GI risk |
|---|---|
| Gels heavy in fructose without matching glucose | Gels led by glucose or maltodextrin, or a glucose-fructose blend you have practised with |
| Whole fruit during the run | Gels or chews made for sport |
| Juice or soda at full strength | A 6 to 8 percent sports drink |
| High-fibre energy bars | Low-fibre chews or blocks |
| Dairy-based products, if you are sensitive | Dairy-free versions |
The drink concentration rule most runners break
This is the single highest-yield fix in the whole article. Fluids leave the stomach fastest when they are close to the concentration of body fluids. Drinks above roughly 8 percent carbohydrate sit in the stomach, pull water in from the body, and produce exactly the cramping and sloshing runners complain about.
Water
Approx. carbohydrate concentration0 percent
Behaviour during runningEmpties fastest; carries no fuel
Standard sports drink
Approx. carbohydrate concentration6 to 8 percent
Behaviour during runningDesigned to empty quickly while delivering fuel
Fruit juice
Approx. carbohydrate concentration10 to 12 percent
Behaviour during runningToo concentrated; dilute roughly half and half
Regular soft drink
Approx. carbohydrate concentration~11 percent
Behaviour during runningToo concentrated, and carbonation adds distension
A gel taken without water
Approx. carbohydrate concentrationEffectively very high
Behaviour during runningThe most common self-inflicted cramp; always chase a gel with water
Modern high-carb race drink mixes
Approx. carbohydrate concentrationOften 14 to 20 percent
Behaviour during runningSpecialist products with modified formulations; require real gut training
| Drink | Approx. carbohydrate concentration | Behaviour during running |
|---|---|---|
| Water | 0 percent | Empties fastest; carries no fuel |
| Standard sports drink | 6 to 8 percent | Designed to empty quickly while delivering fuel |
| Fruit juice | 10 to 12 percent | Too concentrated; dilute roughly half and half |
| Regular soft drink | ~11 percent | Too concentrated, and carbonation adds distension |
| A gel taken without water | Effectively very high | The most common self-inflicted cramp; always chase a gel with water |
| Modern high-carb race drink mixes | Often 14 to 20 percent | Specialist products with modified formulations; require real gut training |
The gel-without-water case is worth repeating because it accounts for a large share of mid-race cramping. A gel is a concentrated syrup. Swallowed dry, it needs your body to supply the water to dilute it, and it pulls that water out of circulation into your gut at exactly the moment you need it elsewhere. Take gels at a water station, not between them.
- Take each gel with about 150 to 250 ml of water. A few good mouthfuls from a cup or bottle is enough.
- On long or hot runs, use an electrolyte drink with roughly 300 to 600 mg of sodium per 500 ml. Sodium helps your gut absorb the fluid.
Runner’s stomach: the lower-gut version
Cramping low in the abdomen, with urgency and sometimes diarrhoea, comes from a different mechanism. During hard exercise, blood is redistributed away from the digestive tract toward working muscle and skin, and gut blood flow can fall substantially. The intestinal lining is sensitive to that reduction, and the resulting combination of reduced absorption, altered gut permeability, and mechanical jostling produces the classic runner’s trots.
Because the driver is intensity, this problem gets worse in races rather than in training, which is precisely when it is least welcome. The controllables are what you ate in the previous 24 hours, how hot it is, whether you are dehydrated, and whether you take NSAIDs.
- Reduce fibre for the 24 hours before hard sessions and races. This is temporary and race-specific; a high-fibre diet is good for you the rest of the time.
- Try a low-FODMAP day before hard efforts if you are symptom-prone. Controlled work in runners has found meaningful symptom reduction from short-term FODMAP restriction.
- Avoid ibuprofen and similar NSAIDs before and during long runs. They increase gut permeability and are associated with worse gastrointestinal symptoms and, at extremes, kidney risk.
- Stay ahead of dehydration. Losing more than about 2 percent of body mass worsens gut symptoms as well as performance.
- Establish a reliable pre-run toilet routine, including a consistent wake-to-start interval and caffeine timing, rather than leaving it to chance.
Train the gut like any other system
The most under-used remedy is also the most effective one: the gut adapts. Repeatedly taking carbohydrate during training increases intestinal transporter density and gastric emptying capacity, and reduces symptoms at a given intake. Runners who eat nothing on every long run and then attempt 60 g per hour on race day are asking an untrained system to perform on demand.
1 to 2
Carbohydrate per hour on long runs30 g
FocusOne familiar product, always with water
3 to 4
Carbohydrate per hour on long runs45 g
FocusFix a schedule, for example every 25 minutes
5 to 6
Carbohydrate per hour on long runs60 g
FocusIntroduce a glucose-fructose blend
7 to 8
Carbohydrate per hour on long runs70 to 90 g if targeting that range
FocusRehearse at race pace, not just easy pace
Race week
Carbohydrate per hour on long runsRepeat the exact plan you have practised
FocusNo new products, no new concentrations
| Week | Carbohydrate per hour on long runs | Focus |
|---|---|---|
| 1 to 2 | 30 g | One familiar product, always with water |
| 3 to 4 | 45 g | Fix a schedule, for example every 25 minutes |
| 5 to 6 | 60 g | Introduce a glucose-fructose blend |
| 7 to 8 | 70 to 90 g if targeting that range | Rehearse at race pace, not just easy pace |
| Race week | Repeat the exact plan you have practised | No new products, no new concentrations |
Practise at goal race intensity at least a few times. Fuel tolerance at easy pace tells you very little about tolerance at threshold, because the underlying problem is blood flow, and blood flow tracks intensity.
One caveat on the blend step. A small number of runners never tolerate fructose well, however much they practise. If fructose-containing products keep causing trouble, stay on glucose or maltodextrin fuels. Glucose alone absorbs at up to about 60 g per hour, which still covers most training runs.
A troubleshooting checklist
- Did I drink a large volume in the 30 minutes before starting? Reduce it and sip instead.
- Was my last meal within 2 hours, or high in fat, fibre, or protein? Move it earlier or simplify it.
- Am I taking gels without water? Pair them, every time.
- Is my drink more concentrated than about 8 percent? Dilute it.
- Did I eat a lot of fibre or FODMAPs yesterday? Reduce them before hard sessions.
- Did I take ibuprofen? Stop taking it around long runs.
- Am I trying to consume more carbohydrate than I have ever practised? Build up over weeks.
- Did I wait until I felt hungry to start fuelling? On runs that need fuel, take the first dose 20 to 30 minutes in and keep to a schedule.
- Did symptoms start as I pushed my intake up? Cut in-run carbohydrate by about 20 to 30 percent for a while, then build back gradually.
- Is this new, persistent, or present at rest? See a doctor rather than adjusting your breakfast.
Frequently asked questions
Why do I get stomach cramps when I run?
Usually one of three things: a side stitch from a distended stomach irritating the abdominal lining, undigested food that has not left the stomach, or reduced gut blood flow at high intensity causing lower abdominal cramping. Timing, drink concentration, and the previous day’s fibre intake explain most cases.
How do you get rid of a side stitch while running?
Slow down, breathe deeply into the belly rather than the chest, press firmly into the painful spot while exhaling, and try changing which foot strikes as you exhale. Raising the arm on the painful side and leaning away also helps. It usually resolves within a minute or two of easing off.
What causes runner’s stomach?
Blood flow is redirected away from the digestive tract during hard exercise, which reduces absorption and irritates the intestinal lining. Fibre and FODMAPs eaten the day before, dehydration, heat, NSAIDs, and concentrated drinks all make it worse.
What should I eat before running to avoid stomach cramps?
Simple carbohydrate that is low in fat and fibre, eaten 2 to 3 hours before: white toast with jam, a bagel with honey, white rice, or a ripe banana. Closer to the run, shrink the portion and lean on liquids.
Should I run through a stomach cramp?
A side stitch can usually be run through after easing the pace and adjusting your breathing. Cramping with nausea or urgency is better handled by slowing until it settles. Any pain that continues after you stop running, or that is severe, needs medical attention rather than persistence.
Does dehydration cause stomach cramps when running?
It contributes. Once fluid losses exceed about 2 percent of body mass, gastric emptying slows and gastrointestinal symptoms become more likely, which is why cramping is more common in heat and in long events.
Why do I get stomach cramps when I take gels?
Usually one of three reasons: the gel went down without water, it is heavy in fructose without matching glucose, or you took it during a hard surge when gut blood flow is already low. Take each gel with about 150 to 250 ml of water, choose one led by glucose or maltodextrin, and take it on a steadier stretch of the run.
Should I stop eating during a run if my stomach hurts?
Not always. Cut back your carbohydrate for a while, keep sipping fluid, and return to small, frequent doses once it settles. Stopping all fuel on a long run just swaps a stomach problem for an energy crash. If the pain is severe or does not ease, stop running and get it checked.
How long does gut training take?
Most runners notice less discomfort within 2 to 4 weeks of fuelling on 1 to 2 runs a week. Reaching 60 g per hour usually takes 5 to 6 weeks, and 70 to 90 g per hour at race pace around 8 weeks, following the progression above.
Sources
- 1Exercise-Related Transient Abdominal Pain (ETAP)Sports Medicine (Morton and Callister, 2015)Prevalence, the peritoneal-irritation mechanism, and the fluid link
- 2Gastrointestinal Complaints During Exercise: Prevalence, Etiology, and Nutritional RecommendationsSports Medicine (de Oliveira, Burini and Jeukendrup, 2014)Causes of upper and lower gastrointestinal symptoms and practical prevention
- 3Systematic Review: Exercise-Induced Gastrointestinal SyndromeAlimentary Pharmacology and Therapeutics (Costa et al., 2017)Splanchnic blood flow reduction and gut permeability during exercise
- 4Low FODMAP: A Preliminary Strategy to Reduce Gastrointestinal Distress in AthletesMedicine and Science in Sports and Exercise (Lis et al., 2018)Short-term FODMAP restriction and symptom reduction in runners
General guidance for healthy adults, not medical advice. Talk to a doctor or registered dietitian if you have a health condition, take medicines or have special dietary needs. Caffeine advice is for healthy adults only. EFSA's safe limit is 200 mg in one dose and 400 mg in a day.
