Altitude Sickness

Written by April Khan and Winnie Yu | Published on August 16, 2012
Medically Reviewed by George Krucik, MD


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, which often shows up as headaches and insomnia. Altitude sickness generally occurs at altitudes of 8,000 feet and above. People who aren’t accustomed to these high altitudes are most vulnerable.

Altitude sickness shouldn’t be taken lightly. The condition can be dangerous. Altitude sickness is impossible to predict, and anyone can get it.

What Are the Types of Altitude Sickness

Altitude sickness is classified in 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, and 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?

As you go higher up in altitude, the air becomes thinner and less oxygen-saturated. Other causes of altitude sickness include extreme cold, low humidity, increased ultraviolet (UV) radiation, and decreased air pressure.

Who is At Risk for Altitude Sickness

You are at low-risk if you’ve had no previous episodes of altitude sickness. Your risk is also low if you’ve gradually increased 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 are ascending rapidly and climbing more than 1,600 feet per day.


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:

  • blue, gray, or pale skin discoloring
  • 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. If there are rattling or crackling sounds in your lungs, you may have fluid in your lungs, which 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?

Early symptoms of altitude sickness can be relieved by descending immediately. However, if you have advanced symptoms of acute mountain sickness, you should seek medical attention.

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

Other treatments may include a lung inhaler, high blood pressure medication (nifedipine), and a phosphodiesterase inhibitor medication to reduce pressure on the arteries in your lungs. If you cannot breathe on your own, you can receive assistance from a breathing machine.

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 is 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 are experiencing symptoms. Descend if symptoms get worse while you’re at rest.

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