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Travel health information for people travelling abroad from the UK

Altitude and Travel


Travel to destinations at high altitude is no longer a rare occurrence. In South America travellers may traverse passes in the Andes often above 4000m, e.g. the Inca Trail in Peru. Trekkers in the Himalayas, especially in Nepal, often reach similar heights as they attempt to reach Everest base camp at 5500m. Kilimanjaro in Tanzania and Mount Kenya are both more than 5000m and are popular challenges for various charity fund raising events.

High AltitudeVery High AltitudeExtreme 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/repatriation is strongly recommended for those travelling to area of high altitude.

Travelling to destinations at high altitude can be exciting, challenging and rewarding, however there are risks associated with this environment. Travellers may experience altitude sickness, a condition also known as Acute Mountain Sickness (AMS), exposure to ultraviolet radiation and cold.

Acute Mountain Sickness

At altitude the air pressure is lower (‘thinner’) than at sea level and gets lower as you climb higher. This means that there is less oxygen in each breath you take; 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). Anyone can suffer from AMS regardless of age, gender, level of fitness or training.

Signs and Symptoms of AMS

AMS may become apparent after 6-12 hrs spent at an altitude of 2500m or higher but symptoms may also be felt at lower levels and take longer to develop (more than 24hrs).

  • Headache.
  • Nausea/vomiting.
  • Loss of appetite.
  • Fatigue.
  • Breathlessness.
  • Poor sleep.

Prevention of AMS

  • If possible chose 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.
  • Get lots of rest.
  • 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.
  • Gradual ascent is the most important preventive measure.
  • Consider using a medication called acetazolamide (Diamox) to aid acclimatisation if gradual ascent is not possible. Diamox 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, prophylaxis may be stopped after 2-3 days at target altitude. For those ascending to a high point and then descending to a lower level, prophylaxis 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.
  • Do not climb more than 300m a day when above an altitude of 3000m. If this is not possible then 2 rest days are recommended.
  • One full rest day is recommended every 3 days.
  • 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 form of the illness: High Altitude Cerebral Oedema (HACE) and High Altitude Pulmonary Oedema (HAPE).

HAPE is caused by fluid gathering in the lungs and HACE by fluid gathering in the brain. 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 following conditions should seek medical advice well in advance of planning to do so:

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

Climate Considerations

Sun Protection

The higher the altitude, the higher the exposure to ultraviolet (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 ultraviolet 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 sunblock/sunscreen regularly.

Further Information

Academic Unit of Respiratory Medicine

The British Mountaineering Council

Travel at High Altitude Information Booklet

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