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Travel health information for people travelling abroad from the UK

Altitude and Travel


Travelling to destinations at high altitude can be exciting, challenging and rewarding. Travellers going on high altitude excursions, treks or expeditions must research thoroughly, plan and prepare carefully (in some instances may include physical training) well in advance of travel, particularly if inexperienced in high altitude travel.

High Altitude Very High Altitude Extreme Altitude
Between 2400-3658m Between 3658-5500m Between 5500-8848m
  • Cochabamba, Bolivia
  • Bogota, Colombia
  • Quito, Ecuador
  • Cuzco, Peru
  • La Paz, Bolivia
  • Lhaza, Tibet
  • Everest Base Camp
  • Mt Everest summit

Good medical insurance that covers medical evacuation and repatriation is strongly recommended for those travelling to area of high altitude.

There are risks associated with high altitude including exposure to ultraviolet (UV) radiation, cold and the risk of developing Acute Mountain Sickness (AMS).

Climate Considerations

Sun Protection

The higher the altitude, the higher the exposure to UV radiation.
Protection against UV light should include:

  • Wearing clothing that covers the skin and is impermeable to ultraviolet light.
  • Using a sunscreen that protects against UVA, UVB and UVC with a high sun protection factor (at least SPF15).
  • Lips, ears and nose should be protected with a high protection sunblock.
  • Wearing sunglasses which filter out UV light (preferably wrap around style).
  • A facemask or balaclava may be required to protect against cold and sun at very high and extreme altitude.

Cold Protection

In areas at very high altitude, low temperatures combined with low oxygen levels increases the risk of frostbite. The risk is even greater in those who already have poor circulation e.g. Raynaud’s disease.

To help prevent injury from the cold:

  • Wear correctly fitting clothes that are approved for cold climates; gloves, hats, socks, boots.
  • Keep hands and feet dry, change wet socks and gloves promptly.
  • Wear goggles at very high altitudes.
  • A facemask or balaclava may be required to protect against cold and sun at very high and extreme altitude.
  • Cover up against the sun, wind and cold.
  • Apply sun block/sunscreen regularly.

Acute Mountain Sickness

At altitude the air pressure is lower than at sea level and gets lower as you climb higher. This means that although the amount of oxygen in the air remains constant, the amount of absolute oxygen in the lungs and the blood is less.

Oxygen is necessary for energy and for the body to function normally. The body will adapt to lower oxygen levels and responds by breathing faster and deeper and making more red blood cells to carry oxygen around. This response, called acclimatisation takes around 3-5 days to occur but will vary between individuals and conditions.

AMS is more likely to occur in those who do not take time to acclimatise properly or arrive directly at areas of high altitude e.g. Cusco in Peru (3300m). The higher and faster the ascent, the more likely that AMS will occur. Anyone can suffer from AMS regardless of age, gender, level of fitness or training.

Signs and Symptoms of AMS

Symptoms of AMS do not usually develop immediately upon arrival but occur during the first 36 hours at altitude.  There is a wide variation in the rate of onset  and the height at which they occur. Early, mild symptoms are similar to that of a hangover.   

  • Headache.
  • Dizziness.
  • Nausea/vomiting.
  • Loss of appetite.
  • Fatigue, flu like symptoms.
  • Breathlessness.
  • Poor sleep and irregular breathing during sleep.

AMS can be diagnosed using the Lake Louise Symptom Score (LLSS), a self assessment score for adults:

Symptoms Severity Points

- No headache

- Mild headache

- Moderate headache

- Severe headache, incapacitating






- No gastrointestinal symptoms

- Poor appetite or nausea

- Moderate nausea or vomiting

- Severe nausea or vomiting, incapacitating





Fatigue and / or weakness

- Not tired or weak

- Mild fatigue/weakness

- Moderate fatigue/weakness

- Severe fatigue weakness, incapacitating





Dizziness / lightheadedness

- Not dizzy

- Mild dizziness

- Moderate dizziness

- Severe dizziness, incapacitating





Difficulty of sleeping

- Slept as well as usual

- Did not sleep as well as usual

- Woke up many times, poor nights sleep

- Unable to sleep.





Anyone who has recently ascended to over 2500m and has a score of 3 or more should be considered to have AMS.

Prevention of AMS

  • Gradual ascent is the most important preventive measure.
  • Choose a trip with time for gradual acclimatisation built in.
  • Ideally avoid flying directly to areas of high altitude.
  • Take 2-3 days to acclimatise before going above 3000m.
  • Do not climb more than 300m a day.
  • Have a rest day every 600 – 900m of ascent or every 3 – 4 days.
  • Maintain a good intake (not excessive) of fluids.
  • Gentle exercise only for the first 24 hrs.
  • Eat a light but high calorie diet.
  • Avoid alcohol.
  • Consider using a medication called acetazolamide (Diamox) which increases blood and tissue oxygenation at high altitude and is useful for some (but not all) individuals. It can be prescribed by your GP or Travel Advisor if felt appropriate for you.
    • Diamox 125mg twice daily can be taken as a trial at sea level for two days before a visit to high altitude. It should be started 24 hours before ascent. For individuals ascending to and staying at  one height for several days, Diamox may be stopped after 2-3 days at target altitude. For those ascending to a high point and then descending to a lower level, Diamox should be stopped once descent has begun.
    • It is a diuretic so urine output will be increased.
    • Using Diamox does not rule out the need for gradual ascent and will not prevent AMS if other advice is disregarded. It will not mask the signs of AMS.
  • Be aware of the signs and symptoms of AMS and recognise them early. Let someone know that you are beginning to feel unwell.

Treatment of AMS

  • If early signs and symptoms of AMS are noticed then stop and rest at that level.
  • Do not go any higher.
  • Take analgesics to treat any headache e.g. ibuprofen or paracetamol.
  • Take anti-sickness medication if necessary e.g. promethazine.
  • Maintain a good fluid intake.
  • Once fully recovered ascent can begin again with care.
  • If the symptoms of AMS do not improve over a day then descent of 500-1000m is necessary.


If AMS is ignored and ascent continues then there is a real risk that the condition will rapidly progress to either or both of the two serious forms of the illness: High Altitude Cerebral Oedema (HACE) and High Altitude Pulmonary Oedema (HAPE).

HACE by fluid gathering in the brain and symptoms include:

  • Severe headache.
  • Drowsiness.
  • Becoming confused or irrational.
  • Unsteadiness.
  • Vomiting.

HAPE is caused by fluid gathering in the lungs and symptoms include:

  • Breathlessness including at rest.
  • Marked fatigue.
  • Fast pulse.
  • Bluish discolouration of the skin (cyanosis).

Both conditions are medical emergencies and require medical attention as soon as possible. Both conditions can be rapidly fatal and descent must be carried out immediately. The person suffering from these conditions should be carried down to the lower altitude as added exertion would worsen their condition. If descent is problematic, air evacuation by helicopter (if available) may be required.

Pre-existing Medical Conditions

If appropriate care is taken, most people can travel to high altitude destinations. However, travellers with the certain medical conditions are more likely to be affected by their condition at altitude and expert medical advice should be sought,

This includes:

  • Diabetes.
  • Asthma.
  • Chronic obstructive pulmonary disease.
  • Epilepsy.
  • Heart conditions.
  • Lung conditions.
  • Pregnancy.
  • Sickle cell disease.

Further Information

This website is produced by UK doctors and aims to provide information about high altitude and its effect on the body. It includes several useful interactive altitude calculators and detailed tutorials about altitude sickness and also allows individuals who may have had HAPE to register on a HAPE database.

This website provides support for those carrying out medical expeditions. The Travel at High Altitude booklet is an excellent resource for those planning a trip at altitude and for carrying with them

British Mountaineering Council

Information for Doctors/Climbers/Trekkers.

British Mountaineering Council Website: is very comprehensive and informative with additional records e.g. prevention of mountain sickness.


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