Stop the Trots! Is Imodium Safe for Runners?

imageExperiencing ass issues (assues) while running? You’re not alone. Go on any group run and inevitably the conversation will turn to poop. That’s because, when it comes to running, not many things give runners more anxiety than poop.

Raise your hand if you’ve ever arrived at the turn-around of your favorite out-and-back route, the one with no bathrooms along the way, only to suddenly realize you HAD TO GO, suffering as you fought off the urge all the way home. And then there’s poop and racing. The thought of having a race interrupted by the need to hit a porta-potty or worse, not making it to one in time, is the stuff of our nightmares. Maybe this is why, next to caffeine, Imodium is many runner’s favorite drug!

But is Imodium safe for runners to use? We decided to investigate!

Why Does Running Give Us the Trots?

Assues, or the sudden-onset of needing to poop, is common among runners, particularly for those of us who run long. Exactly why isn’t totally clear, but several things seem to be contributing factors. Running can speed up your metabolism, which moves food through your digestive system more quickly. Meanwhile your internal organs jostle around from the movement, which just adds to the effect. Additionally, blood flow decreases to your intestines as your muscles require more. On race morning, your pre-race anxiety can lead to your stress hormones increasing which also has a stool-loosening effect.

What is Imodium?

Imodium (loperamide) is an over-the-counter remedy for diarrhea. It works by slowing the digestive tract. It’s considered an essential drug like Tylenol or ibuprofen, so is cheap and widely available. It is meant to be taken in reaction to diarrhea, not as a preventative. But, as you’ll see, that’s not how most runners use it.

How Runners Use it

In my informal survey, runners generally used Imodium preventatively, dosing right before the start of long runs or long races, regardless of the current looseness of their stool. Some also began with a pill upon waking and many also carried another dose to swallow mid-run. Although this is off-label use, it appears quite common even for doctors to recommend it as a prophylactic measure.

Side Effects

While the side effects are fairly short-lived, it’s worth taking a closer look:

  • dizziness
  • drowsiness
  • dry mouth
  • nausea
  • constipation (uh … duh?)

Many runners take Imodium before races and do not experience any of these side effects, but keep in mind you might. Definitely practice a trial dose on a training run to make sure you can run through any possible side effects. Also consider consulting with your doctor before taking it preventatively, especially if you are taking other medications or have any underlying medical issues.


Keep in mind that diarrhea happens for a reason. Sure, sometimes it may be an unfortunate reaction to nerves or to the bouncing of running but occasionally it’s a necessary function, expelling the bad stuff if you have food poisoning or allergies, for example. And of course if diarrhea is a common occurrence for you then it’s time to have an honest chat with your doctor to consider if you have an underlying medical condition causing your assues.

In addition, many runners (myself included) have noted that Imodium does not prevent running-related assues, Imodium warns it can take up to 48-hours to have an effect and, for some, it may even make their poop problems worse!

Imodium Alternatives

If you want to avoid drugs, period, try these non-medication tips if you fear an assues flare-up:

  • Track and reduce possible triggers: dairy, gluten; dehydration; artificial sweeteners; stress; caffeine; or other medications.
  • Practice what foods work for you before racing and then stick to them. The day before or morning of a race is not a good time to experiment with new foods.
  • Avoid high-fiber foods before a race and eat no closer than two-hours before your race.
When ya gotta go, ya gotta go.

Sometimes shit happens no matter how careful you are. To handle having to go mid-run or race here are some tips to make it less of a horrifying experience:

  • Wear dark-colored shorts. Skirts help hide any accidents as well.
  • Generously apply anti-chafe product such as Aquaphor.
  • Carry TP or, even better, wet wipes in a baggie.
  • Don’t stress about time lost if you do have to make a pit-stop during a race. It may seem long, but it’s possible to get out of a potty in just a minute or two and it is always much better than finishing the race with the shit happening down your leg.

Have you experienced assues? What’s your remedy? Is it really better to be sleepy than to have to hide poop in your shorts?

I'm a 20-year veteran of competitive running, USATF certified coach, mom of a toddler -- and still trying to set PRs. I write about training from 5k to marathon, motherhood and competitive running, and the elite side of the sport. The 5k is my favorite race (16:56 PR) but I've got a score to settle with the marathon.

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  1. Ahh. Story of my life. Then my “assues” (perfect term!) ended with a spa day in the local hospital the day before the marathon I trained my butt off for. Whomp whomp. I was diagnosed with “runners ischemia” and there is no fix. I constantly took Immodium before long runs and races during that training cycle and it was really hit or miss on whether it would work. I had one 20 where I didn’t have to stop once, and then a 14 miler which I stopped once or twice during (and then was on the freaking toilet ALL DAY long after).

    Although I am currently only training for a half. I am still putting in decent milage and have really had zero issues since my hospital stay. Staying hydrated before, after and during runs seems to be the biggest key for me. I also eliminated artificial sweetners from my diet, and will cut out dairy a week before my goal race.

    Stupid poop.

    1. Wow, glad you’re not having any more assues, Marion! That’s great that better hydration seemed to fix things. I’ve also (tried to) cut out dairy recently and am seeing some improvement so I think I’m going to have to get more strict about it.

  2. Has anyone tried probiotics (long term) as a means to help as well? I am fortunately on the mild side of GI issues but that’s mostly because I go 5x before long-runs, races and have cut back dairy significantly in my diet and stopped eating “danger foods” before LR/races. I have had mild success with just swigging antacids before runs as it settles the stomach which seems to trigger overall GI issues. I have been trying daily probiotics but I’m not 100% consistent in taking and that probably limits the effectiveness. I know the studies are few but I feel like the next decade will all be about bacteria curing all these woes. Just not sure the OTC capsules are the cure all yet.

    1. I hope someone pops in with experience on this question!

      I’ve tried probiotics but am inconsistent with taking them. (I forget about them since they need to be in the darn refrigerator.)

  3. I use straight up peppermint oil – I’ll drink it in a mug of hot water before a long run (helps me relax and calm the nerves before a race) and rub it directly onto my lower belly. I don’t know if it’s a placebo effect or what, but knock on wood, no assues!

  4. I have crohn’s disease and a nervous stomach, so yeah, I use immodium before races. Only side effect I’ve had is constipation.

    1. That gives me hope! I have Ulcerative Colitis and I’ve been in a flare since August and my first full marathon is this Saturday! I decided I’ll give the Imodium a try, my last long run I stopped twice and didn’t leave the potty the rest of the day

  5. I have had these assues for a number of years. I have had a colonoscopy and whatever the other one is and ruled out any other issues including dairy and celiac. They did find some hemaroids but didn’t treat them – pity as they flared up again recently on a 35 k trail run. No real idea of what brings this on, except if I can’t poop before a run, then I know I’m going to be in trouble.
    Has anyone tried sanitary pads? On some of my long trail runs there aren’t any toilets – just the bush and not always a spot where you can be discrete and go potty. I’ve had horrid experiences having to finish a run having pooped my pants and the smell, well just lets say others could tell.
    Any good ideas?