Sign up for our newsletter
Get health tips, wellness advice, and more

Thanks for signing up!
You've been added to our list and will hear from us soon.

See all Healthline's newsletters »

Altitude Sickness


When you’re flying, mountain climbing, hiking, or driving at a high altitude, your body may not get enough oxygen.

The lack of oxygen can cause altitude sickness. Altitude sickness generally occurs at altitudes of 8,000 feet and above. People who aren’t accustomed to these heights are most vulnerable. Symptoms include headache and insomnia.

You shouldn’t take altitude sickness lightly. The condition can be dangerous. Altitude sickness is impossible to predict — anyone at a high elevation can get it.

What Are the Types of Altitude Sickness

 Type 1

Altitude sickness is classified into three groups:


Acute mountain sickness (AMS) is considered the most common form of altitude sickness. The symptoms of AMS are very similar to being intoxicated.


High-altitude cerebral edema (HACE) occurs if acute mountain sickness persists. Symptoms of HACE resemble AMS. It also causes drowsiness and confusion. If not treated immediately, HACE can cause death.


High-altitude pulmonary edema (HAPE) is a progression of HACE, but it can also occur on its own. Symptoms of HAPE include increased breathlessness during exertion, coughing, and weakness.

If HAPE isn’t treated promptly by decreasing altitude or using oxygen, it can cause breathlessness when resting or death.

What Causes Altitude Sickness?


If your body does not acclimate to high elevations, you may experience altitude sickness. It’s most common at elevations above 8,000 feet. Twenty percent of hikers, skiers, and adventurers traveling to high elevations under 18,000 feet experience altitude sickness. The number increases to 50 percent at elevations above 18,000 feet.

As altitude increases, the air becomes thinner and less oxygen-saturated. Other causes of altitude sickness include:

  • extreme cold
  • low humidity
  • increased ultraviolet (UV) radiation
  • decreased air pressure

Who Is at Risk for Altitude Sickness?

Risk Factors

You’re at low-risk if you’ve had no previous episodes of altitude sickness. Your risk is also low if you gradually increase your altitude. Taking more than two days to climb 8,200 to 9,800 feet can help reduce your risk.

Your risk increases if you have a history of altitude sickness. You’re also at high risk if you ascend rapidly and climb more than 1,600 feet per day.

What Are the Symptoms?


The symptoms of altitude sickness can show up immediately or gradually. Symptoms of altitude sickness include:

  • fatigue
  • insomnia
  • headache
  • nausea
  • rapid heart rate
  • shortness of breath (with or without exertion)

More serious symptoms include:

  • skin discoloration (a change to blue, gray, or pale)
  • confusion
  • coughing
  • coughing up bloody mucus
  • chest tightness
  • decreased consciousness
  • inability to walk in a straight line
  • shortness of breath at rest

How Is Altitude Sickness Diagnosed?


Your doctor will listen to your chest using a stethoscope. Rattling or crackling sounds in your lungs can indicate fluid in your lungs. This requires prompt treatment. Your doctor may also do a chest X-ray to look for signs of fluid or lung collapse.

How Is Altitude Sickness Treated?


Descending immediately can relieve early symptoms of altitude sickness. However, you should seek medical attention if you have advanced symptoms of acute mountain sickness.

The medication acetazolamide can reduce symptoms of altitude sickness and help improve labored breathing. You may also be given the steroid dexamethasone.

Other treatments include a lung inhaler, high blood pressure medication (nifedipine), and a phosphodiesterase inhibitor medication. These help reduce pressure on the arteries in your lungs. A breathing machine may provide assistance if you can’t breathe on your own.

What Are the Complications of Altitude Sickness?


Complications of altitude sickness include:

  • pulmonary edema (fluid in the lungs)
  • brain swelling
  • coma
  • death

What Is the Long-Term Outlook?


People with mild cases of altitude sickness will recover if it’s rapidly treated. Advanced cases of altitude sickness are harder to treat and require emergency care. People in this stage of altitude illness are at risk of coma and death due to brain swelling and the inability to breathe.

Can You Prevent Altitude Sickness?


Know the symptoms of altitude sickness before you ascend. Never go to a higher altitude to sleep if you’re experiencing symptoms. Descend if symptoms get worse while you’re at rest.

Read This Next