Altitude sickness is a common condition that can occur when you climb to a high altitude too quickly.

The decrease in atmospheric pressure makes breathing difficult because you aren't able to take in as much oxygen. Most cases are mild, with symptoms that can include:

  • headache  
  • nausea
  • dizziness
  • exhaustion

In rare cases, altitude sickness can cause fluid to build up either on the lungs or the brain. These are very serious conditions and require immediate medical attention. Symptoms of severe altitude sickness can include:

  • a bubbling sound in the chest
  • worsening breathlessness 
  • coughing up pink, frothy liquid
  • clumsiness and difficulty walking
  • confusion leading to loss of consciousness

Read more about the symptoms of altitude sickness and the complications of altitude sickness.

What to do if you have symptoms

If you have mild symptoms of altitude sickness, you shouldn't go any higher for at least 24 to 48 hours. You can continue to climb if your symptoms improve after this.

If your symptoms get worse or don't improve after 24 to 48 hours, you should descend by at least 500m.

Severe altitude sickness is a medical emergency. Someone with severe symptoms should immediately descend to a low altitude and seek medical help.

Read more about treating altitude sickness.

Preventing altitude sickness

Proper acclimatisation to altitudes of about 2,500m (just over 8,200 feet) or more is the best way to prevent altitude sickness. It usually takes a few days for the body to get used to a change in altitude.

Ascending slowly will give your body time to adapt to the change in altitude. For example, once you're above 3,000m (10,000 feet) try not to increase the altitude at which you sleep by more than 300-500m a night. Keeping hydrated is also important, but make sure you avoid alcohol.

Read more about preventing altitude sickness.

Who's affected by altitude sickness?

Altitude sickness is fairly common among those who spend time at high altitudes, such as mountaineers and skiers.

In its mildest form, altitude sickness can occur at heights over about 2,500m (8,000 feet) above sea level, which is a common height for many ski resorts.

However, the more severe symptoms of altitude sickness tend to occur at altitudes of 3,600m (about 12,000 feet) and above.

It's not possible to get altitude sickness in the UK because the highest mountain, Ben Nevis in Scotland, is only 1,344m (4,406 feet) high.

There are no specific factors, such as age, sex or physical fitness, that increase a person's likelihood of getting altitude sickness. Certain people are affected, while others are less susceptible to it. Just because you haven't had it before doesn't mean you won't develop it on another trip.

Page last reviewed: 28/04/2015

Next review due: 28/04/2017