Why do you feel so awful at high altitudes?

A drop in air pressure and oxygen can make you feel pretty out of shape

February 26, 2015
The best advice for warding off altitude sickness? Take it easy, and descend closer to sea level. [Image credit: Flickr user Steve Hicks]

Your chest heaves, lungs burning, but you can’t catch your breath. Your head pounds, vision blurring, but you feel like you’ll faint any second. You’re definitely fit enough to climb a flight of stairs without trouble — is this some sort of nightmare?

Possibly, but if you’re up in the mountains, you’re more likely experiencing altitude sickness. When you travel to a place above about 8,000 feet, your body starts telling you there’s something seriously wrong with the air up there. The “thin” air at high altitudes has considerably less oxygen and pressure. This is because the earth’s gravity holds the oxygen close to the surface — so much so that half of the oxygen in the atmosphere is found below 18,000 feet. For comparison, Mount Everest is about 29,000 feet. The highest inhabited town in the world is La Rinconada, Peru in the Andes Mountains at nearly 17,000 feet.

With so much less oxygen, your body has to breathe more to get the same amount of the essential molecule. This leads to the shortness of breath, dizziness and tiredness indicative of altitude sickness. The oxygen drop combined with the decreased air pressure packs a one-two punch to your cardiovascular system. In order for your lungs to breathe air in without duress, the pressure has to be higher outside your body. But at high altitudes, the outside air pressure is lower than it is inside your lungs, making it more difficult to pull in the thinner air and for your veins to pump oxygen throughout the body. As a result, heart rate and blood pressure skyrocket as your body kicks into overdrive. This can lead to more unpleasant symptoms, including headache and confusion.

If altitude sickness goes untreated, though, it could become something much worse: High-Altitude Pulmonary Edema or High-Altitude Cerebral Edema. Both conditions are characterized by extreme breathlessness and tiredness, and could result in death within 24 hours. About one in 10,000 skiers in Colorado get HAPE, according to the Centers for Disease Control and Prevention. Since you could experience altitude sickness, or worse, in an airplane cruising above 23,000 feet, airlines pressurize the cabin to make the air inside feel like you’re closer to the ground.

Doctors commonly prescribe the drug Acetazolamide (brand name Diamox) for patients to take a day or two before they ascend to high altitude locales and for a couple days after they get there. The drug makes your body feel like you’re at a high altitude, so a lot of the symptoms of altitude sickness are side effects. It works by increasing the amount of gases, namely oxygen, the lungs can absorb and then distribute to the blood. Combining Acetazolamide or altitude sickness with alcohol can severely exacerbate the negative effects (trust me).

To limit the effects of the sickness when traveling to high altitudes, you can also avoid exercise, drink plenty of water, and of course, go to a lower altitude. After a few days at high altitude, you should be acclimated to the new height. Your body kicks up production of red blood cells so it can transport more oxygen, making you feel much more normal.

When you return to sea level, the increased oxygen flow will probably make you feel 10 years younger — until your cardiovascular system returns to normal in a few weeks, that is.

About the Author

Rebecca Harrington

Rebecca graduated from the University of Minnesota-Twin Cities in 2014 with a B.S. in Biology and a B.A. in Journalism. She worked at the U’s student newspaper the Minnesota Daily, where she discovered her passion for explaining the complexities and bizarre aspects of science to non-scientists. You can often find her cooking without recipes, discussing scientific explanations for everything around her, and laughing at the little surprises in life.



Wiliam Deckelman says:

Is there the possibility of high altitude visits helping PAH patients?

MedStudent says:

“Thin air” does not have less oxygen. The percentage is the same as sea-level air. The air pressure at high altitudes is not lower than the air pressure in your lungs. If this was the case, it would be physically impossible for air movement into the lungs. Lastly, veins do not pump oxygen throughout the body. They return oxygen depleted blood to the heart.

Kenneth M. says:

Take plenty of breaks if you are hiking up these altitudes.

J Carlson says:

I would like to see you print a correction on this article so that you help stop spreading the myth that there is less oxygen at higher altitudes. This is completely wrong…just google atmospheric pressure for a real scientific explanation.

jon hooper says:

yes your correct its the same anywhere on earth about 21% its the barometric pressure that makes you feel short of breath


“making it more difficult to pull in the thinner air and for your veins to pump oxygen throughout the body.”
This statement is technically incorrect. The HEART “pumps” oxygen-carrying blood throughout the body, through the ARTERIES. The VEINS return the oxygen-spent blood to the heart and lungs.

Paul says:

In case someone has the different high altitude effects, such as headaches when flying, does it help to live at high altitude for some time to get used to the pressure?

Ashley says:

High altitudes causes a severe health reaction, such as on Mount Everest, and this is because of the low amount of oxygen molecules in the air. Take Mt. Kilimanjaro for example, it has 630 molecules per breath contrasting to the 1000 molecules per breath at sea level. At a certain point, this can result in death.

Matt says:

The oxygen concentration is still 21% no matter what altitude you at until you get into the 50,000 plus foot range. Its the partial pressure that affects how much Oxygen you actually can breath in. So its no that there is less Oxygen in the air its just got a lower pressure being excreted on it. See Grams gas law..

Carlie King says:

I understand the theory of low altitudes (Mesa, AZ) not benefiting a COPD patient any more than (for example) an altitude of 3,000 – (average American altitude). Does the theory that a “dry” (Phoenix) climate is better for the COPD patient than (for example) San Antonio, which is more humid? Is this a myth also?

bitch says:

bitch naw

Donna Frost says:

Why is it on a recent trip to Denver, CO, I not only suffered being short of breath the entire 9 days but also couldn’t carry on a halfway intelligent conversation with my family? It was as though I had left my brain in NC. Could not think right at all, as though I was a different person.

Donna Frost says:

I forgot to mention I suffer from both asthma and COPD. SO SORRY.

Ibrahim Shebl says:

it is a known fact 1400 years ago, but now you present the reason change in pressure …. makes one sure he is right !!

Brown says:

No, that fact did not discover 1400 years ago. The person who discovers this as a fact was Paul Bert. In 1878, he published a book on his barometric pressure research. His book called From Physiology to Barometric Pressure. He discussed in his book altitude sickness. Although, I search to find if somebody else discovers that fact; I did not find anybody. But what I found a religion book (Quran), mention { يُضِلَّهُ يَجْعَلْ صَدْرَهُ ضَيِّقًا حَرَجًا كَأَنَّمَا يَصَّعَّدُ فِي السَّمَاءِ} which means {He makes his breast tight and constricted as though he were climbing into the sky} (Alan’amm, 125). Quran was filly written in 632 C.E. I’m actually surprised how can a person climes this fact in the 7th century.


Anthony says:

@Medstudent What you have said is true but you should at least give her some credit. She has the general idea.

Mike says:

Are there any studies done on people who have the opposite problem? At sea level up through an altitude of 1,000-2,000 feet or so, I feel like I’m breathing sludge. The time when I lived in the Denver suburbs was much better, but to really feel like I could breathe freely I had to go up into the mountains, around 10,000-14,000 feet. Physically activity was easier up there.

As an aside, I’m finding it amusing that people are objecting that “thin air” does not have less oxygen. It most certainly DOES have less oxygen – per unit volume, that is. Since you breathe in a certain volume of air, not a certain number of molecules, the fact that both sea level air and high-altitude air are about 21% oxygen does not change the fact that a full breath of high-altitude air has fewer oxygen molecules in it than a full breath of sea level air.

A literal chemist, check the website. says:

You pedantic bitches, none of yall should be allowed to comment. No s*** higher altitudes have less oxygen PER BREATH, all the “armchair scientists” can shove it up their a**. Yall likely had to google what percentage of the air is Oxygen, just to sit there and say “hurr durr oxygen is the same percentage everywhere on earth”. do you know what does change with elevation? THE VOLUME OF AIR, OXYGEN, CO2 EVERYTHING, ENTERING RHE LUNGS. That is what the article says, and that is a scientific fact.

Scienceline pbs says:

I think these are nice comments about high altitudes and great facts

Scienceline pbs says:

like the comments

Justin Barnard says:

I should think that it would be fairly obvious to any scientist, or even a med student, that with the percentage of oxygen not changing and the volume of lungs staying the same that there would be less moles of oxygen

Francisco says:

I was driving over the mountains in colorado n i felt like i was gonna pass out n my heart started beating so fast my whole body was shaky while driving n i knew i had to get to lower altitude so i continued driving has this happened to anyone. I live in colorado just at a lower altitude

Charlie says:

When I am above 6k feet I eventually feel like the life force is leaving me and I return to lower altitudes asap. My blood pressure increases I hear my heart pounding in my head and worry that it’s detrimental to my well being.

Steven says:

I have that same problem mike I live at sea level I feel like I’m breathing sludge also when I was on vacation at 6500 feet it felt so much better. I’m not sure what my ideal altitude is to be honest but one reason I found why I’m acclimated to altitude is severe ADHD I wonder if you have that I’m not sure how I would do at 10-14000 feet since I haven’t slept higher then 7000 feet in 9 years but I’m the only one I know with this problem I also do much better in cold weather to I live in south Florida btw and I’m pretty much as unacclimated to south Florida as can be.

Steven says:

Well Mike if you ever do read this page again, I just came back after 18 days I notice that when I was in Leadville when I breath the same way as I breath in Florida (forcing out oxygen I would get altitude sick) but when I took deep breaths and breath efficiently I got relaxed seems like at sea level I breath heavy force out oxygen, at 6500 I do that still but much less of it at 10100 feet I do none of it I can breath freely there just like you. I’m still not sure however how I would do at 14000 feet. I’m quite sure your from south Florida just like me right and I’m guessing you stayed at that lifeskills program in Denver.

Christine says:

It’s a myth that there is less oxygen at higher altitudes. The air’s composition is constant, regardless if you are at sea level or on Mt. Everest. The lower pressure changes the way the body processes the available oxygen and less of it reaches the cells. A scientific article should have noted this!

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