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Altitude and Travel


Travelling to destinations at high altitude can be exciting, challenging and rewarding. However there are risks associated with high altitude including developing altitude sickness, exposure to ultraviolet (UV) light and cold temperatures.

You should have travel insurance that covers you for travelling to altitude.  Your policy should have cover that includes medical evacuation and repatriation home if necessary.

Some destinations at high altitude include:

High Altitude Very High Altitude Extreme Altitude
Between 2,400-3,658m Between 3,658-5,500m Between 5,500-8,848m
  • Cochabamba, Bolivia
  • Bogota, Colombia
  • Quito, Ecuador
  • Cuzco, Peru
  • La Paz, Bolivia
  • Lhaza, Tibet
  • Everest Base Camp, Nepal
  • Mount Everest summit, Nepal
  • Mount Kilimanjaro, Tanzania 5,895m

Altitude Sickness

At altitude the air pressure is lower and this means there is less oxygen available to your body when you breath. We need oxygen for our bodies to work properly. The process of your body adapting to the lower oxygen levels is called acclimatisation and it takes about 3 to 5 days.  If your body does not get enough time to acclimatise to being at high altitude, you can develop altitude sickness (sometimes called mountain sickness). Altitude sickness usually happens at levels above 2,500m.

  • Altitude sickness can develop very quickly and can be life threatening.

There are 3 types of altitude sickness:

Acute Mountain Sickness

Acute Mountain Sickness (AMS) is more likely to occur if you go to high altitude too quickly and there is not enough time to acclimatise properly.  Even if you are physically fit, you can still suffer from AMS.

Signs and Symptoms of AMS

Symptoms of AMS do not usually happen immediately but start to show a few hours after being at a high altitude.  Symptoms can be mild to begin with, often being likened to having a hangover.  Symptoms you might get can include:

  • headache
  • loss of appetite
  • being sick or feeling like you want to be sick
  • feeling very tired
  • flu like symptoms
  • dizziness
  • poor sleep and irregular breathing during sleep

If symptoms of AMS are ignored, you can go on to develop more severe and life threatening types of mountain sickness called HAPE or HACE

Preventing AMS

The best way to prevent AMS is to give your body enough time to acclimatise to being at a higher altitude. 

You can do this by not travelling too quickly to altitudes above 2,500m

  • Take the first 2 to 3 days to acclimatise to being at altitudes below 2500m before going any higher.
  • If you can, avoid flying directly to somewhere at high altitude, but if unavoidable acclimatise before any further ascent.
  • If you are climbing or trekking, then a slow, gradual ascent is advised.

The major cause of AMS is going too high too quickly.

The Wilderness Medical Society recommend that once you are at an altitude of 2,500m, you should:

  • not sleep more than 500m higher than you slept the night before
  • have a rest day every 3 to 4 days

It is also important that you:

  • make sure you drink enough water so you do not get dehydrated
    • you may need to drink 4 to 5 litres of safe water to avoid getting dehydrated
  • avoid drinking alcohol
  • eat a light but high calorie diet

Treatment of AMS

  • be aware of the signs and symptoms of AMS and let someone you are travelling with know that you are beginning to feel unwell
  • you should rest at that altitude you are at and not go any higher
  • take painkillers to treat any headache e.g. ibuprofen or paracetamol
  • if your symptoms of AMS do not improve over a day, then you should descend 500 to 1,000m to a lower altitude
  • once your symptoms have gone and you have fully recovered you can ascend again

Medication to prevent AMS

Acetazolamide (Diamox) is a medicine that is sometimes taken to prevent AMS.  It works by speeding up the processes your body goes through to acclimatise to high altitude.  It might be recommended if you have had AMS before or if a gradual ascent is not possible

  • Acetazolamide does not replace the need to acclimatise through a gradual assent.

You should speak with a travel health professional who will be able to advise further on using Diamox. 

In South America, Coca tea or Mate de Coca is sometimes suggested for preventing AMS. There is no evidence that this prevents AMS and should not be taken to treat or prevent AMS.


If the signs of AMS are ignored and you continue to go higher, you are at risk of developing life threatening altitude sickness,  High Altitude Cerebral Oedema (HACE) and/or High Altitude Pulmonary Oedema (HAPE).

HACE is due to swelling of the brain.  Symptoms include:

  • severe headache
  • unsteadiness or not being able to walk in a straight line
  • being sick
  • drowsiness
  • becoming confused or irrational

HAPE is caused by fluid gathering in your lungs. Symptoms include:

  • breathlessness even when you are resting
  • feeling very weak
  • fast pulse
  • bluish discolouration of the skin (cyanosed)

Both conditions are an emergency and can quickly result in death; descending to a lower altitude must be carried out immediately.

Pre-existing Medical Conditions

If you have certain medical conditions, you should get advice from the health care professional that manages your condition or a travel health professional before travelling to altitude. These conditions include:

  • diabetes
  • epilepsy
  • heart conditions
  • lung conditions including chronic obstructive pulmonary disease (COPD) and moderate/severe asthma
  • sickle cell disease

  It is important to make sure that your underlying condition:

  • is as stable as possible
  • will not be made worse by travelling to altitude
  • is covered by your travel insurance


If you are pregnant and travelling to altitude then you should discuss your travel plans with your midwife or obstetrician before you travel.

Other Considerations at Altitude

Sun Protection

The risk of exposure to Ultra Violet (UV) light is greater at higher altitudes.  The risk of sunburn is increased when UV light is reflected, for example, off snow.

To protect against UV light, you should:

  • wear clothing that covers your skin and blocks out UV light
    • a facemask or balaclava may be required to protect your face against the cold and sun at very high and extreme altitude
  • use a sunscreen that protects against UVA, UVB and UVC light with a high sun protection factor (at least SPF15)
  • protect exposed skin such as lips, ears and nose with a high protection sunblock
  • wear sunglasses which filter out UV light to protect your eyes

More information on minimising exposure to the sun can be found on our sun safety page.

Cold Protection

Frostbite is a risk in areas at very high altitude due to low temperatures combined with lower oxygen levels in your blood. The risk is even greater if you have poor circulation. To help prevent injuries from the cold you should:

  • wear correctly fitting clothes that are approved for cold climates; gloves, hats, socks, boots
    • a facemask or balaclava may be required to protect your face against cold and sun at very high and extreme altitude
  • keep your hands and feet dry, change wet socks and gloves promptly
  • wear goggles to protect your eyes at very high altitudes

Further Information

Altitude Physiology Expeditions
British Mountaineering Council
Medex: Travel at high altitude booklet
Wilderness Medical Society

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