Altitude sickness is when your body doesn’t have time to adjust to lower oxygen availability higher up in the atmosphere. It’s usually preventable and treatable. When severe, it can rapidly turn into a life-threatening concern. Recognizing the symptoms early is key to pausing your ascent, which can head off complications or worsening symptoms.
Altitude sickness is the term for medical conditions that can happen when you move to a higher altitude too quickly. The higher up you go, the thinner the atmosphere gets. That means breathing in the same amount of air gets you less oxygen than at a lower altitude. Altitude sickness happens when your body has trouble adjusting to the difference in how much oxygen you’re getting with each breath.
Altitude sickness can refer to three distinct conditions:
Altitude sickness is common among people who aren’t acclimated, meaning they’re not used to breathing at high altitudes. AMS is rare below 8,000 feet (2,438 meters) above sea level. Almost everyone who ascends quickly to 11,000 feet (3,352 meters) will develop AMS.
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Altitude sickness can cause many symptoms, and these can vary depending on the severity. The symptoms of acute mountain sickness usually appear within the first day or so of reaching a high altitude. More severe forms like HAPE or HACE take longer to appear, usually between two and five days.
The symptoms of AMS include:
Given time, your body can usually adapt to altitude-related changes that affect how much oxygen you get with each breath. Without enough time to adapt, altitude sickness is the result.
The risk factors for altitude sickness often relate to the altitude itself or how you get there.
A common misconception is that your physical health is a risk factor for developing altitude sickness. It isn’t, but altitude sickness can make symptoms of some existing conditions worse. Examples include anemia and chronic obstructive pulmonary disease (COPD).
Altitude sickness can become deadly if AMS turns into HAPE or HACE. HAPE can be deadly within 12 hours. HACE can be deadly within 24 hours. That’s why recognizing altitude sickness of any kind is critical to preventing severe complications.
A healthcare provider can diagnose altitude sickness based on your symptoms and a physical exam. That includes checking your breathing, blood pressure and heart rate. They’ll also ask questions about what you’re experiencing and how you feel. They may also check your coordination or other abilities to see if you have any signs of a more serious condition like HAPE or HACE.
Altitude sickness often happens in locations that are remote and don’t have readily available medical equipment. By the time you descend to lower elevations where you can receive more advanced medical care, your symptoms are improved or gone entirely. However, medical testing is still possible when you reach a place where more advanced care is available.
Tests that may help diagnose or treat altitude sickness include:
There’s only one way to “cure” altitude sickness outright: descend to a lower altitude.
Several treatments can help altitude sickness when it’s not as severe. Some of these are also helpful when an immediate descent isn’t possible. Treatment approaches include:
Complications can vary depending on the treatment you receive, especially medications. Your healthcare provider is the best person to tell you what complications you might experience or should watch for.
How quickly you feel better depends strongly on the severity of your altitude sickness and the treatments you receive. Descending to a lower altitude is the fastest way to feel better, and most people feel progressively better as they descend.
People who choose to stop and acclimate may have symptoms that last several hours or up to a day. Minor symptoms usually stop within a day or two as your body gets used to the altitude.
Altitude sickness is very preventable, and there are a few key ways you can prevent it. They are:
For most people, altitude sickness doesn’t get beyond acute mountain sickness, the mildest form. A headache is the most common — and often the earliest — symptom of acute mountain sickness. If you notice you have a headache or other mild symptoms and stop ascending, your symptoms should remain the same. After a day or two, they should stop.
Milder forms of altitude sickness usually only last a few days. The symptoms should disappear once your body gets used to the higher altitude.
When altitude sickness is more severe, however, it can get worse quickly. The more severe forms of altitude sickness, HAPE and HACE, can be deadly within 24 hours. Because of that, keeping altitude sickness from worsening is critical. Recognizing the symptoms of HAPE and HACE, such as trouble breathing (even while resting) or clumsiness (ataxia), is crucial.
The outlook for altitude sickness depends on the severity, how you react to the symptoms and how you respond to treatment. If you ignore symptoms and keep ascending, you’ll likely experience worsening symptoms. Ascend too quickly, and you’re more likely to develop dangerous complications.
If you experience more disruptive symptoms of acute mountain sickness, especially nausea or fatigue, you should stop ascending. They’re a warning that you’re at risk for more problems if you keep going.
If you experience symptoms of HAPE or HACE, especially trouble breathing or loss of coordination, descend immediately (if possible). They’re signs of life-threatening complications.
If you develop symptoms of altitude sickness, the best thing you can do right away is not make it worse. Stop ascending, or descend if you can. Resting and limiting exertion are also helpful. Try to make it as easy as possible for your body to adjust to the altitude.
If you use tobacco products, you should quit before going to high altitudes. Tobacco use of any kind can affect oxygen levels, which is a key concern with altitude sickness. If you use tobacco products, stop. Your healthcare provider can guide you and offer resources on how to do so before you travel.
If you have altitude sickness, modifying your diet is usually not necessary. But you should avoid alcohol for the first couple of days after you arrive at a high altitude. Alcohol can make some of the symptoms of altitude sickness worse. You should also be sure to get plenty of fluids to avoid dehydration, which can worsen some altitude sickness symptoms.
You should talk to a healthcare provider before traveling to a high-altitude destination. They can advise you on precautions to take that’ll be helpful for your specific needs. They may also be able to advise you on preventive measures or prescribe medications that can prevent altitude sickness.
You should get emergency medical care (at a hospital, emergency room or another facility or setting that’s applicable) if you experience more serious symptoms of altitude sickness.
The most important symptoms to watch for are:
These are all symptoms of more severe forms of altitude sickness. Both these other forms, HAPE and HACE, can be deadly within hours. Treating them as soon as possible is essential.
The milder form of altitude sickness, acute mountain sickness, isn’t dangerous (as long as you don’t keep ascending). It’s unpleasant and disruptive but should resolve in a day or two.
The more severe forms of altitude sickness, HAPE and HACE, are life-threatening medical emergencies. They need immediate care.
A note from Cleveland Clinic
Altitude sickness is a widespread issue for people traveling to higher elevations. If you experience the symptoms, take them for the warning signs they are. Stop ascending and descend if you can. Resting and giving your body time to acclimate are the best ways to get past altitude sickness. Treatments can also help you feel better.
Altitude sickness is often very preventable. A flexible schedule can make a big difference, allowing time to acclimate to higher altitudes. Medications can also help. And if you experience more severe symptoms, don’t ignore them.
Last reviewed by a Cleveland Clinic medical professional on 08/21/2023.
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