Nausea during high altitude cycling climbs

Question

Please accept my apology if this question is not related to this forum, but I am desperate to find the solution of my problem. I have a great interest in cycling climbs. However, I have a problem: when I do high altitude climbs, I often start feeling nauseous and vomit.

When a tough climb starts, the first thing that happens is that my thirst disappears, and I can’t drink much water. Then, I start feeling something weird in my stomach, and if I drink water, I feel nauseous. It feels like the water is stuck in my stomach.

However, there have also been incidents where I experienced these symptoms even after long rides that didn’t involve much climbing. For example, one day I traveled 182 KM without taking many pauses, and when I reached home, I started feeling nauseous. There is a hill about 26 KM from my house, which is at an altitude of 2700 meters (8,800 ft), while my house is at 1200m (3,900 ft). Every time I climb that hill, I inevitably vomit upon reaching the top. This year, during two different climbs, when I crossed 1800m altitude (5,900 ft), I started feeling nauseous. However, last year, I climbed to an altitude of about 4173m (13,700 ft) and didn’t feel nauseous, and the weather was cold.

Some people suggest that this happens to me due to dehydration, and in some cases, I suspect it might be due to high altitude climbs, but I’m not sure. One definite problem is that during tough exertion climbs, I stop feeling thirsty or hungry. If any member has experienced similar symptoms, can I get some guidance? Thank you all very much.

Answer 1

Medical questions are off-topic here, so the question may be closed (at least for the guidance part).

Nausea is among the symptoms for altitude sickness, as is it is as well for exercise that is too hard compared to what the body can sustain. That may be a plausible explanation, but there are other factors that I’m not aware of. Training to ride at high altitude is definitely out of my comfort zone, so I can only recommend to find a coach that can suggest you appropriate sessions for that purpose.

It is also common to not be hungry or thirsty when doing exercise, and many athletes are having some kind of reminder if they can’t count on their « feeling ». Personally I display the moving duration and the distance already ridden on my bike computer, and use that as a base to know when to eat or to drink. In summer, I also have periodic reminders on the bike computer (the kind that you need to mark as complete explicitly) with reminders to drink. When riding in club, I also use a water bladder so that I can drink safely when riding in tight groups - because I’m not at ease to drink from a bottle when riding in such environment, but that can also apply when riding off-road. These are little tips, but what you need to drink and at which frequency depends obviously on your metabolic requirements.

On altitude sickness, when I was in the worst of my physical shape, I got dizziness at about 1500m when hiking (another symptom of altitude sickness, but hiking is not as demanding as cycling), when coming for day hikes from my place, that was at 200m. I could go to 2000m after a few days of acclimatation, but altitude was a hard limit.

Answer 2

I'm going to answer as if there's nothing medical underlying this, because it's not an uncommon problem. But that's an assumption you might want to get tested.

Dehydration has strange effects, including nausea, and high altitude can be dehydrating.

I certainly find it hard to recover from dehydration while out, and your "It feels like the water is stuck in my stomach" is a good description. It may be worth trying electrolyte tablets in (some of) your water; I tend to use them under-strength, one to a big bottle instead of one to a small bottle.

A similar feeling comes with nutrition - too long running on empty, particularly climbing or fighting a headwind with no food, and your ability to digest a feed becomes compromised. You may get on with getting a lot of your calories from energy drinks routinely but the slower release of solid carbs works better for me.

Caffeine is also relevant. Too much, too soon, with too much milk, or without sugar are all issues I or riding buddies have suspected of leading to nausea.

On long rides (400km and up, or very hilly 300km+) I have a reminder popping up on my phone to eat, drink (and stretch) because for me the key is to not get behind.

So my suggestion to you is to address hydration, nutrition, and electrolyte provision from early in the ride. I've also found some relief from nausea with ginger sweets - there's actually scientific evidence for ginger against nausea (though not vomiting, I believe) and the sugar is helpful in that state.

Answer 3

I would like to extend my heartfelt thanks to the experts on this forum for their valuable suggestions regarding my nausea during high-altitude cycling climbs. After some research, I discovered the solution to my specific problem and wanted to share my experience here. Please note that these are my personal experiences and solutions and should not be considered medical advice. My age is 44 years!

To find a solution, I studied numerous articles and watched videos on how high-altitude climbers manage their ascents. I focused particularly on Mount Everest climbers and their safety protocols. I discovered that there are two primary factors likely causing my nausea:

• Ascending too quickly (due to the speed of the bicycle)
• Dehydration from extreme exertion and losing moisture through breathing in the thin, low-oxygen atmosphere.

To address dehydration, I started using electrolyte powder, which also helped with muscular fatigue. Additionally, I made more frequent stops for water intake to stay hydrated.

Acclimatizing to a low-oxygen environment posed a unique challenge. Ascending slowly is critical for adjusting to low oxygen levels at high altitudes, but on a bicycle, slow isn't always an option. Further research led me to the medication "Acetazolamide," commonly used by climbers to accelerate acclimatization. Additionally, a doctor recommended "Ondansetron" to counter nausea. After testing both medications on high-altitude climbs, I found that taking Acetazolamide (125 mg) in the morning and Ondansetron (8 mg) during the final sections, combined with constant electrolyte intake, effectively prevented altitude sickness.

Testing the solution

After these discoveries, I performed some high-altitude climbs to test the effect of these medications. During all these climbs, I ate dates to maintain my nutrition levels. I don’t have many food choices available because I have been a patient of Ulcerative Colitis for the past 11 years.

The first climb involved an elevation gain of 1,925 meters over 33.10 km. The climb started at an altitude of 1,200 meters and reached a maximum altitude of 2,700 meters. The final 6 km section was above 2,500 meters. Usually, I always get nauseous on this track, but this time, I felt no nausea. I took Acetazolamide in the morning of the climb and Ondansetron during the final section.

In the second climb, I traveled 102.88 km with a total elevation gain of 2,263 meters. The final 10 km of the climb were above 2,000 meters, with a maximum altitude of 2,450 meters. I started at 1,200 meters at the beginning of the climb. I wanted to understand whether it was Acetazolamide controlling my nausea or the anti-nausea medication Ondansetron. So, I didn't take Acetazolamide before the climb, and as I reached 1,800 meters, I felt nauseous. I took Ondansetron, but despite that and taking electrolytes throughout the climb, I vomited upon reaching 2,000 meters. My condition improved after I began to descend.

The third climb involved an elevation gain of 1,613 meters over 29.52 km, with the last 6 km above 2,500 meters. The starting altitude was 1,200 meters. This time, I took Acetazolamide in the morning and didn't take Ondansetron until we reached the destination and took some rest. At that moment, I felt a little nauseous, so I took an 8 mg Ondansetron, and my nausea disappeared within 20 minutes.

After these trials and testing my body, I was ready for the final big climb that I had been preparing for over the last six months. Using a similar protocol, I took Acetazolamide in the morning. It was a climb of 19.65 km with an elevation gain of 2,023 meters. The altitude at the start of the climb was 1,700 meters. The last 8 km were above 3,000 meters. I kept myself hydrated and used electrolytes when I felt muscular fatigue, which then disappeared. At 3,500 meters, I felt a bit nauseous, so I took an 8 mg Ondansetron, and my symptoms improved.

After all these trials, I hope I have resolved my issue of feeling nauseous during high-altitude climbs with the combination of three items, acetazolamide, ondansetron, and electrolytes. My all the climbing activities are recorded on my Strava profile as well as on my YouTube channel.

Answer 4

In my experience the cure for altitude sickness is to drink as much as you can. This conclusion came from living at sea level and frequently driving to Yosemite and hiking at altitudes over 8000 ft.

As I got close I would force myself to drink between 1 and 2 quarts of water. I found this to always be effective. I never really understood the mechanism. My guess was that as your body gets less oxygen it tends to increase the volume of blood circulating, causing dehydration. I really don't know, this was just the best guess I could come up with.

I would drive to Yosemite, then start hiking at about 8000 ft. in the afternoon. I had few problems if I drank enough before starting.