Oh Sh*t! What Happens When You Really Need a Poo While Running?

Originally published May 2022. Updated July 2026.

I first wrote this article a few years ago. I’ve now updated it with a better explanation of why running can make you need the toilet, what you can do about it, and when repeated bowel problems might need checking.

There are some running problems people are happy to talk about.

A tight calf. Heavy legs. Feeling out of breath. A watch that refuses to connect to GPS.

Needing an urgent poo when you are miles from the nearest toilet does not usually make that list.

It is embarrassing, inconvenient and, once the feeling becomes strong enough, very difficult to ignore.

I briefly mentioned toilet problems in my article about common issues you can avoid with a pre-run checklist (5 Common Problems You Can Avoid Using Your Pre-Run Checklist). However, it probably deserves an article of its own because most regular runners will either experience it themselves at some point or know someone who has.

I have been caught short many times during more than 25 years of running.

Unfortunately, the first two times I was out with running clients.

So, why can running suddenly make you need the toilet, what can you do to reduce the chances of it happening, and what should you carry in case your digestive system ignores all your careful planning?

Why can running make you need a poo?

The simple explanation I used to give was that everything gets jiggled around while you run.

There is some truth in that. Running creates repeated movement and impact through your abdomen, which can make sensations from your bowel harder to ignore.

However, that is not the whole explanation.

Exercise can affect how quickly food and waste move through your digestive system. During harder or longer runs, more blood is directed towards the muscles that are working and less may be available for digestion. Heat, dehydration, nerves and the intensity of the run can add to the problem.

This helps explain why someone might feel perfectly comfortable before starting, only to experience rumbling, cramping or a rapidly increasing urge to find a toilet once they are running.

Lower gastrointestinal symptoms such as urgency, loose stools, abdominal discomfort and diarrhoea are commonly reported by endurance runners. They appear to be particularly common during longer or harder exercise.

For most people, the occasional urgent toilet stop is unpleasant rather than medically concerning. However, it is still worth trying to understand what tends to trigger it for you.

Food may be part of the problem, but there is no single culprit

My wife, Siân, once came extremely close to being caught short during a run after eating spicy food the night before.

She made a video about the experience, and I am fairly sure she has avoided repeating that particular pre-run experiment ever since.

Spicy food can be a trigger for some people, but it is not the only food that may cause problems.

Depending on the person, difficulties may be more likely after:

• A large meal eaten too close to running.
• A particularly fatty meal.
• A sudden increase in fibre.
• Large amounts of caffeine.
• Foods containing sugar alcohols, which are found in some low-sugar products, chewing gums, gels and drinks.
• Dairy products if you do not tolerate them well.
• A very concentrated sports drink or more carbohydrate than your gut is used to processing.
• Particular high-FODMAP foods.

That does not mean runners need to avoid all these foods.

A food that causes problems for one person may be completely fine for someone else. You may also tolerate something before an easy 30-minute run but struggle with the same food before a hard session or a half marathon.

The aim is to notice patterns rather than start removing large groups of foods unnecessarily.

If bowel problems happen regularly, keep a simple record of:

• What you ate and drank beforehand.
• How long before the run you ate.
• The distance and intensity of the run.
• Whether it was particularly hot.
• How nervous or stressed you felt.
• What symptoms occurred and when they started.

You may begin to see a fairly obvious pattern.

Short-term reductions in certain high-FODMAP foods may help some athletes who experience repeated digestive problems, but the research is still developing. A restrictive low-FODMAP diet should not become the default advice for every runner, particularly without support from a suitably qualified dietitian.

Should you try to go before running?

It is sensible to give yourself time to use the toilet before you leave, particularly before a longer run, race or session where toilets will be difficult to reach.

Running at a similar time of day and following a familiar routine may also make your bowel habits more predictable.

For example, some runners find that getting up, having a drink, eating breakfast and allowing enough time before leaving gives their body a chance to do what it needs to do.

Caffeine can stimulate the bowel, which may be useful if it is already part of your routine. However, suddenly drinking several strong coffees before an event in the hope of forcing the issue could create the exact problem you are trying to prevent.

You should not sit on the toilet and strain simply because you think you ought to go.

You also cannot guarantee that your bowel is completely empty before you run. Even with a familiar routine and sensible preparation, you can still be caught out.

Think about the run you are doing

The amount of planning needed should match the run.

Before a short run close to home, you may not need to think about it much at all.

Before a long run, race or route through an isolated area, it makes sense to know:

• Where the available public toilets are.
• Whether cafés, leisure centres or other facilities will be open.
• Where you could shorten the route and get home.
• Whether you need to carry a small emergency kit.

For races, look at the event information rather than assuming toilets will be available whenever you need one. Start-area toilets often have long queues, and toilets on the course may be several miles apart.

Trying new foods, gels, drinks or pre-workout products on race morning is also asking for trouble. Practise your race-day nutrition during training so your gut has some idea what is coming.

What should you do when the urge starts?

Do not automatically try to run through it.

Sometimes an early rumble settles. At other times, continuing to run turns a manageable warning into a genuine emergency.

Slow down or walk briefly and work out what your realistic options are.

Can you:

• Turn around and get home?
• Use a nearby public toilet?
• Stop at a café or leisure centre?
• Call someone for help?
• Adjust your route towards somewhere with facilities?

It may feel embarrassing to ask to use a toilet, but it is usually less embarrassing than the alternative.

Well-known elite runners have experienced the same problem. Paula Radcliffe famously stopped at the roadside during the 2005 London Marathon before continuing and winning the race.

Running ability does not make anyone immune from bowel urgency.

What happens when there genuinely is no toilet?

Sometimes you are a long way from home, there are no facilities nearby, and waiting is no longer an option.

I have been in that position more than twice.

The first time, I was not carrying toilet paper or wipes. I had to use leaves.

That brings me to an important piece of advice: make sure you know what plant you are grabbing.

One of my clients once managed to use a nettle leaf. Somehow, it stayed in place until the end of the run. I will leave the rest of that story to your imagination.

Since my own first incident, I have carried a small emergency toilet kit on longer or more isolated runs.

Mine includes:

• A small amount of toilet paper or a few wipes in a sealed bag.
• A separate bag for carrying used paper or wipes to a bin.
• Hand sanitiser.

Ordinary toilet paper is usually a better option than relying on wet wipes. It is lighter and creates less persistent waste.

Never leave wet wipes behind, including wipes described as biodegradable or flushable. They may remain in the environment for a long time and should always be carried out and disposed of properly.

If you have no alternative but to go outdoors, be considerate.

Move well away from paths, homes, picnic areas, farmland and places where other people are likely to stop. Stay away from streams, rivers and other water sources. Follow any local rules or signs, and carry all wipes, bags and other non-degradable waste away with you.

A proper toilet should always be the first choice when one is reasonably available.

Can you stop runner’s diarrhoea completely?

Probably not.

You can reduce the likelihood of problems by:

• Learning which foods and drinks you tolerate.
• Allowing enough time after larger meals.
• Practising your fuelling during training.
• Avoiding unfamiliar products before important runs.
• Planning routes around available toilets.
• Carrying a small emergency kit when necessary.
• Managing the intensity of the run if your stomach already feels unsettled.

Hydration matters too, but drinking a huge amount immediately before running is unlikely to solve anything. Drink normally across the day rather than trying to correct poor hydration in the final few minutes before leaving.

The gut can also adapt to consuming carbohydrate during exercise. If you need gels or sports drinks for longer events, gradually practising with them can improve your tolerance rather than introducing a full race-fuelling plan all at once.

Sometimes, despite doing everything sensibly, your body will still have other ideas.

Shit happens.

When should you speak to your GP?

Occasionally needing the toilet during a run is common.

Regular diarrhoea, severe pain or a lasting change in your bowel habits should not automatically be dismissed as part of running.

Speak to your GP if you notice symptoms such as:

• Blood in your poo or bleeding from your bottom.
• A persistent and unexplained change in how often you go.
• Regular loose stools or diarrhoea that is unusual for you.
• Ongoing or severe abdominal pain.
• Unexplained weight loss.
• Unusual tiredness or signs of anaemia.
• Symptoms that repeatedly interfere with your training despite changing your routine.

These symptoms are often caused by conditions other than cancer, but they still deserve proper assessment rather than self-diagnosis. The NHS advises seeking medical advice for persistent bowel changes, bleeding, abdominal pain and unexplained weight loss.

A little preparation can save a very awkward walk home

No pre-run routine can guarantee that you will never be caught short.

However, you can make the situation less likely and much easier to deal with.

Learn your usual triggers. Leave enough time before longer runs. Know where the toilets are. Practise the food and drink you intend to use during events.

And when you are heading somewhere remote, carry a little toilet paper and a spare bag.

You may carry them for years without needing them.

But on the day you finally do, you will be extremely glad they are there.

Have you ever been caught short while running?

You can share your story in the comments or send me an email. I suspect there are far more runners with a story like this than are willing to admit it.

Chat again soon,

Barrie