Ironman Nausea

Triathlon Forum
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I’m desperate for answers. As a 9 time IM finisher I suffer from nausea on the run. It’s classic IM symptoms, starts on the run about halfway and forces me to walk. Never in training or 70.3, only fulls. I have tried everything .. my current fuel is all liquid, self mixed maltodextrin/ fructose 90 carbs/ hr on bike, 60g / hr on run. 600g per hour sodium on bike/ 800g on run. Generally on top of hydration. Also have been working with an endurance sports nutritionist. No other GI issues come with this besides dizziness after the nausea as my gut shuts down.

Has anyone ever solved this issue ? Any experience with zofran or other meds?

I can always find tons of people that have this issue but 0 that have solved it. I walked away from my last race at mile 18 and fear I may have to quit fulls for good.

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have you tried removing/reducing fructose from your fueling plan as a test? when you say generally on top of hydration, what is that in terms of liquid volume? 800mg of sodium without enough fluid could lead to problems. if i had to guess, your ability to absorb fructose while under heat/fatigue may be limited and after a long time which is why it happens in a 1406 not 703.

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Thanks! The trouble is that where I to remove the fructose at least from my bike solution, I couldn’t just replace it with maltodextrin because research shows that gut issues can occur above 60g per hour. Fructose is absorbed through a different pathway thus it’s benefit in combining with maltodextrin. On that note I’ve tried fueling with all sucrose solution (table sugar) , gels (huma, gu, spring energy) to no avail, so not sure fructose is the culprit here. But it may be worth trying cutting out the fructose on the run (since I could raise the maltodextrin there since it’s only at 40g per hour) . I may just try that

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Also generally I am taking in about 30 oz of water per hour. And to add, I have tried much lower sodium levels to no avail. Still good call out !

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i think switching to pure glucose on the run is a good call, since you are only doing 60g/hour is a safe way to test this. the problem (if this fructose malabsorption is it) uusally gets worse over time so this could be the easy fix. sucrose is 50% fructose, can you try something like UCAN on the run?

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We’ve got the exact same problem. I’ve finished 16 fulls and have been sick on them all, with the nausea starting around mile 14 on the run. It’s prevented me from having a decent full IM race performance vs I’ve found the podium many times at 70.3 distance where I can ingest about anything with no problems.
I’ve found the major hurdle with getting advice like “did you try this” is that it takes me a full Ironman to test that advice. How many times can you have training days where you swim 2.4, bike 112, and run 13 just to test nutrition/hydration strategies?

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Again good call! I have tried UCAN and also mixing my own waxy maize mix. Again to no avail.

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Totally agree! Even if you do do a full training “test” the race day stress phenomenon would likely not present itself

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I’d fade the carb/sodium intake on the run, no need in taking 60g cho/800g sodium on the run unless you are going to be out there for 5 hours. Fade them as you go, as well as your H2O intake. Maybe start with 45g cho, then maintain with 30g for the rest of the race if you are really terrified of not having enough gas in the tank. Skip the sodium, it could be screwing up your gut osmolality on the run, at that point you probably don’t need it. Any brand telling you that you do is using it as a marketing scheme.
I think we tend to overdo it with nutrition on the run. Try something as simple as alternating every mile with 6oz coke/water in training.

Zofran works by blocking serotonin, providers usually won’t prescribe that for motion sickness either.

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I feel your pain and frustration! I have had the exact same problem. I usually have a great swim/bike and come off the bike feeling fine and at mile 13 almost exactly I start feeling it. I first feel like ok I need more nutrition because I start to fade a little but nothing dramatic. When I add any fuel or liquid at this point I get the nausea, dizziness and a heavy feeling in my shoulders. The nausea usually lasts until the next morning and I have had to drop out of 3 Ironmans because I was reduced to dry heaving and on my hands and knees. I have spent many hours in the med tent post race nauseated and dry heaving. They test my sodium (normal). and give me anti nausea meds which did nothing to help. I do drink and take gels leading up to this point in the race but for some reason at this point in the run everything shuts down. I have tried almost every nutrition out there. I have worked with two nutritionists and practiced with nutrition. I finally wrote it off to age related problems and heat intolerance. The only thing I haven’t tried is backing off the watts on the bike to see if that helps. However my training is very consistent and the coaching I get is great. I have been doing Ironman races since I was 23 and have probably done 30 over the years. This problem started at age 57. I am a 65 year old former female pro and for the life of me cannot figure out what is going on. 70.3’s are not a problem for me. Long training in build up to Ironman races won’t simulate what is going on either. Baffled!

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How about a motion sickness patch? I have thought that might help as it does feel similar to motion sickness.

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Might not hurt trying Scopolamine patches at this point if you want to continue. I have used them whenever I had to use supplemental O2 on HALO/HAHO parachute jumps. If you do want to give them a go, try them out before a training session, they can make you pretty dizzy and drowsy.

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Thanks for sharing! Currently considering trying orally dissolving Zofran as I don’t know that taking anything that needs to be digested would work, assuming my gut is shutting down

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I did have a friend who is a P.A. And her husband was a great triathlete. She suggested the Zofran to prevent the nausea.

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Not sure I will attempt another IM, but I am tempted;) I would love to do Kona one more time. I am a former A.G. World champion in Kona and finished top ten as a pro 5 times so this is so hard for me to accept:(

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Just answered a similar post on another thread. I wouldn’t try any of the fancier solutions until I’d eliminated sodium deficiency as the culprit. Symptoms match. Some people need double what you’re taking.

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I can’t help as far as the full IM stuff: I’ll never do more than a half (and may never do another tri again, but that’s another discussion).

But, I do know zophran: just got over a bout of awful giardia (you don’t want it), and had some zophran leftover. It happened way to close to a benefit ride I was doing, and was still having some nausea on the long rides. Brought some zophran with me, and it really helped me get through it (170 miles, 8.5k feet of gain).

I do not know if there are any downsides of using zophran, or using it too often - there should be enough docs on here that can chime i for that - but as far as using it for getting through an event, it worked for me.

  • Jeff
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I used to get it at the start of the run. I was consuming seven or eight gels on the bike, a carbo pro / sport drink mix, and then water/gatorade provided at aid stations. Way too much sugar. Something about the movement of my stomach going from horizontal to vertical made it brutal to adjust to running.

I cut back on the carbo pro and started to make a point of eating a banana or some solid food on the bike. It worked

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Wow, you and a few other posters in this thread have described exactly my issue! I’ve completed 9 Ironmans and my average time to nausea is around 9 hours or mile 9 of the run. It’s been such a debilitating issue I made a chart of each race day that include: the exact time/ distance to nausea; nutrition/calories/sodium consumed; CTL fitness level; weather conditions…. and I’ve come to the conclusion that despite the nutrition, weather conditions, fitness level, or how easy I go on the bike, the fact remains I encounter debilitating nausea around 9 hours that causes me to throw up and walk.

I used to think it was caused by heat, or solar sickness from being in the sun all day, but this past July was Ironman Lake Placid and it was very cool conditions, little sun, I rode 60% of FTP, I had switched to Infinit custom mix, consumed lots of water, was very fit, and ironically the nausea was the worst it’s ever been. And when I threw up, because I had timed my nutrition well there wasn’t even barely a few cups of stuff coming out of me. When I was younger in my late 30’s, early 40’s, I used to be able to throw up, walk a few miles, then rally and eat and my gut would start back up, but that’s becoming less frequent.

I am going to try going back to introducing more solids on the Bike and try to eat more “whole foods”. My guess is taking in 90%+ of simple sugars all day is what is ultimately shutting down our gut and causing the nausea reaction. I think by carefully introducing some more fiber, fats and proteins, maybe that’ll help? I plan to try this on some long bricks – but as one poster mentioned, it’s very difficult to simulate 9 hours of continuous racing in a training environment! LoL. Although of note, I raced Ironman Maryland in 2023 which had a very shortened swim and even with just 16 minutes of swimming, the nausea still hit, just earlier, around 7 hours in at mile 10 of the run. So for me, I think I can simulate the same problem without the swim.

The solutions I’m going to try separately and then together based on what works are introducing ginger into my drinks; introducing more whole foods on the bike (banana, cliff bar pieces, honey stinger waffles, etc…) ; tums ; pickle juice ; zofran. I’m also switching to flat courses with cooler temps which are typically quicker for me, and I’ve been able to get further into the run just based on time to nausea. Like others I’ve done 20+ half Ironmans, 7 marathons (avg 3:30) and I’ve even done a virtual Everlasting that took 12 and half hours and encountered ZERO NAUSEA during any of these. But for the Eversting I actually ate French toast with maple syrup and got a 10 to 12 minute full rest each time the bike coasted down Alpe du Zwift.

So to conclude, I think I’m going to try and find/ test easily digestible alternative fuel sources that down shut the gut down like sugar does after 9 hours of consistent consumption. Along with some different anti nausea solutions. Planning to try this on some 100 mile rides followed by a long run in the Spring and Summertime of 2026. I’ll report back if I find any success and hope any of you do the same! Keep the faith that we’ll find a solution!

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