Altitude Sickness: What to Know

Medically Reviewed by Sabrina Felson, MD on October 30, 2021
5 min read

Sometimes called “mountain sickness,” altitude sickness is a group of symptoms that can strike if you walk or climb to a higher elevation, or altitude, too quickly.

The pressure of the air that surrounds you is called barometric or atmospheric pressure. When you go to higher altitudes, this pressure drops and there is less oxygen available.

If you live in a place that’s located at a moderately high altitude, you get used to the air pressure. But if you travel to a place at a higher altitude than you’re used to, your body will need time to adjust to the change in pressure.

Any time you go above 8,000 feet, you can be at risk for altitude sickness.

There are three levels of altitude sickness:

Acute mountain sickness (AMS) is the mildest form, and it’s very common. The symptoms can feel like a hangover -- dizziness, headache, muscle aches, nausea.

High-altitude pulmonary edema (HAPE) is a buildup of fluid in the lungs that can be very dangerous and even life-threatening. This is the most common cause of death from altitude sickness.

High-altitude cerebral edema (HACE) is the most severe form of altitude sickness and happens when there’s fluid in the brain. It, too, is life-threatening, and you need to seek medical attention right away.

You might have:

Symptoms usually come on within 12 to 24 hours of reaching a higher elevation and then get better within a day or two as your body adjusts to the change in altitude.

If you have a more moderate case of altitude sickness, your symptoms might feel more intense and not improve with over-the-counter medications. Instead of feeling better as time goes on, you’ll start to feel worse. You’ll have more shortness of breath and fatigue. You may also have:

  • Loss of coordination and trouble walking
  • A severe headache that doesn’t get better with medication
  • A tightening in your chest

If you develop a severe form of altitude sickness like HAPE or HACE, you might have:

  • Confusion
  • Shortness of breath even at rest
  • Inability to walk
  • A cough that produces a white or pink frothy substance
  • Coma

Anyone can develop altitude sickness, no matter how fit, young, or healthy they are -- even Olympic athletes can get it. In fact, being physically active at a high elevation makes you more likely to get it.

Your chance of getting altitude sickness depends on a few other things: how quickly you move to a higher elevation, how high you go up, the altitude where you sleep, and other factors.

Your risk also depends on where you live and the altitude there, your age (young people are more likely to get it), and whether you’ve had altitude sickness before.

Having certain illnesses like diabetes or lung disease doesn’t automatically make you more likely to develop altitude sickness. People who have sickle cell anemia, COPD, unstable angina, a high-risk pregnancy, heart failure, or cystic fibrosis are less likely to be able to tolerate the change in altitude. So are people who have had recent heart attacks or strokes.

If you get a headache and at least one other symptom linked to altitude sickness within a day or two of changing your elevation, you might have altitude sickness. For mild symptoms, you can try staying at your current altitude to see if your body adjusts. Rest, keep warm, and have plenty of liquids. Don’t go any higher until your symptoms are completely gone.   

If your symptoms are severe, or if mild symptoms don’t go away in a couple of days or get worse, get to a lower elevation as quickly as possible. Don’t exert yourself. Get medical help.

Your doctor might listen to your chest with a stethoscope or take an X-ray of your chest or an MRI or CT scan of your brain to look for fluid.

To treat HACE, you might need a steroid called dexamethasone. If you have HAPE, you will need supplemental oxygen and may need medications, as well as moving to a lower altitude.

The best way you can lower your chance of getting altitude sickness is through acclimatization. That means you let your body slowly get used to the changes in air pressure as you travel to higher elevations.

You’ll want to climb to higher altitudes gradually. Going slowly helps your lungs get more air through deeper breaths and allows more of your red blood cells to carry oxygen to different parts of your body.

Some basic guidelines for acclimatization are:

  • Start your journey below 10,000 feet. If you have to fly or drive somewhere that’s higher up, stop at one destination that’s lower for at least a full day before going any higher.
  • If you do fly or drive somewhere and can’t spend time at lower elevations on the way, the drug acetazolamide can help speed up acclimatization.
  • If you walk, hike, or climb over 10,000 feet, only go up an additional 1,000 feet per day. For every 3,000 feet you climb, rest at least a day at that height.
  • “Climb high and sleep low”: If you have to climb over 1,000 feet in a day, make sure you come back down to a lower altitude to sleep.
  • Drink 3-4 quarts of water every day, and make sure about 70% of your calories are coming from carbs.
  • Don’t use tobacco, alcohol, or medications such as sleeping pills, especially for the first 48 hours. Caffeine is OK if you normally drink it.
  • Don’t vigorously exercise for the first 48 hours.
  • Know how to identify the first signs of altitude sickness. Move to a lower elevation right away if you start to have these symptoms.