What is altitude sickness?

Altitude sickness, also known as mountain sickness, can happen if you travel to a high altitude.

Altitude sickness can affect anybody — being young or physically fit does not decrease the risk.

Whether or not you get altitude sickness could depend on:

• your height above sea level
• the time you took to make the ascent
• whether or not you have any problems affecting your heart and lungs

Altitude sickness can be fatal if not treated.

What are the symptoms of altitude sickness?

If you have altitude sickness, you are likely to feel dizzy and weak, you might also have a headache and feel nauseous. It can feel like a hangover.

Altitude sickness can affect your lungs, in which case it is sometimes known as high altitude pulmonary oedema or HAPE. People with HAPE can feel short of breath and have a cough and a racing heart. In extreme cases, their lips turn blue.

Altitude sickness can also cause your brain to swell with fluid, which is sometimes known as high altitude cerebral oedema or HACE. People with HACE can feel confused and irritable and behave in an erratic way.

Altitude sickness can be worse at night and can last for days, even if you stay at the same altitude.

What causes altitude sickness?

Altitude sickness is caused by low oxygen levels in the air at altitudes above about 2,500 metres. It occurs when the body has not had time to adjust to less oxygen.

How is altitude sickness treated?

If you have altitude sickness, you should stay at the same altitude or go lower until the symptoms disappear. Rest, fluids and painkillers are likely to improve the symptoms. Do not continue to climb higher.

It is best not to drink alcohol or take sedatives or sleeping pills because they interfere with the body's adaptation to high altitude.

If you have signs of altitude sickness affecting your lungs or your brain, this is a medical emergency. You need help to descend as soon as possible. Breathing oxygen from a tank can help.

Can altitude sickness be prevented?

If you're planning to travel to a high altitude, consider talking to your doctor about drugs that can help with acclimatisation, particularly if you have had altitude sickness before.

You can reduce the chance of getting altitude sickness by:

• avoiding a rapid ascent from sea level — don't go above about 2,500 metres for the first night's sleep
• once you get above 3,000 metres, ascending by no more than 500 metres per day
• spending the night below the day's highest altitude
• avoiding strenuous exercise before your body has had time to adjust to the lower oxygen levels
• avoiding alcohol at high altitude
• resting for the 48 hours after arriving at a place of high altitude

If you have a medical problem that affects your lungs, heart or circulation, you are at increased risk of getting altitude sickness.