Altitude sickness

All you need to know about altitude sickness, including symptoms, medication, prevention and treatment.

Altitude sickness can occur when you travel to a high altitude too quickly.

Breathing becomes difficult because you aren't able to take in as much oxygen.

Altitude sickness, also called acute mountain sickness (AMS), can become a medical emergency if ignored.

Age, sex or physical fitness have no bearing on your likelihood of getting altitude sickness.

Just because you haven't had it before doesn't mean you won't develop it on another trip.

This page covers:

Symptoms of altitude sickness

Symptoms of altitude sickness usually develop between 6 and 24 hours after reaching altitudes more than 3,000m (9,842 feet) above sea level.

Symptoms are similar to those of a bad hangover.

They include:

  • headache
  • nausea and vomiting
  • dizziness
  • tiredness
  • loss of appetite
  • shortness of breath

The symptoms are usually worse at night.

It's not possible to get altitude sickness in the UK because the highest mountain, Ben Nevis in Scotland, is only 1,345m.

Medication

Consider travelling with these medicines for altitude sickness:

  • acetazolamide to prevent and treat high altitude sickness
  • ibuprofen and paracetamol for headaches
  • anti-sickness medication, like promethazine, for nausea

Preventing altitude sickness

The best way to prevent altitude sickness is to travel to altitudes above 3,000m slowly.

It usually takes a few days for the body to get used to a change in altitude.

You should also:

  • avoid flying directly to areas of high altitude, if possible
  • take 2-3 days to get used to high altitudes before going above 3,000m
  • avoid climbing more than 300-500m a day
  • have a rest day every 600-900m you go up, or every 3-4 days
  • make sure you're drinking enough water
  • avoid alcohol
  • avoid strenuous exercise for the first 24 hours
  • eat a light but high calorie diet
  • avoid smoking

Acetazolamide, available from a travel clinic and, in some areas, your GP, can help prevent symptoms. It's thought to help you adjust more quickly to high altitudes.

You should begin taking the medication 1-2 days before you start to go up in altitude and continue to take it while going up.

If using acetazolamide, you should still go up gradually and follow the general prevention advice.

If you get symptoms of altitude sickness while taking acetazolamide, you should rest or go down until you feel better before going up again.

Treating altitude sickness

If you think you have altitude sickness:

  • stop and rest where you are
  • don't go any higher for at least 24-48 hours
  • if you have a headache, take ibuprofen or paracetamol
  • if you feel sick, take an anti-sickness medication, like promethazine
  • make sure you're drinking enough water
  • avoid alcohol
  • don't smoke
  • avoid exercise

Acetazolamide can be used to reduce the severity of your symptoms, but it won't completely hide them.

Tell your travel companions how you feel, even if your symptoms are mild – there's a danger your judgement can become clouded.

You can continue going up with care once you feel fully recovered.

If you don't feel any better after 24 hours, you should go down by at least 500m (about 1,600 feet).

Don't attempt to climb again until your symptoms have completely disappeared.

After 2-3 days, your body should have adjusted to the altitude and your symptoms should disappear.

See a doctor if your symptoms don't improve or get worse.

Complications

If the symptoms of altitude sickness are ignored, they can lead to life-threatening conditions affecting the brain or lungs.

High altitude cerebral oedema (HACE)

High altitude cerebral oedema (HACE) is the swelling of the brain caused by a lack of oxygen.

Symptoms of HACE:

  • headache
  • weakness
  • nausea and vomiting
  • loss of co-ordination
  • feeling confused
  • hallucinations

A person with HACE often doesn't realise they're ill, and may insist they're all right and want to be left alone.

HACE can develop quickly over a few hours. It can be fatal if it's not treated immediately.

Treating HACE:

  • move down to a lower altitude immediately
  • take dexamethasone
  • give bottled oxygen, if available

Dexamethasone is a steroid medication that reduces swelling of the brain. 

If you can't go down immediately, dexamethasone can help relieve symptoms until it's safe to do so.

You should go to hospital as soon as possible for follow-up treatment.

High altitude pulmonary oedema (HAPE)

High altitude pulmonary oedema (HAPE) is a build-up of fluid in the lungs.

Symptoms of HAPE:

  • blue tinge to the skin (cyanosis)
  • breathing difficulties, even when resting
  • tightness in the chest
  • a persistent cough, bringing up pink or white frothy liquid (sputum)
  • tiredness and weakness

The symptoms of HAPE can start to appear a few days after arrival at high altitude. It can be fatal if it's not treated immediately.

Treating HAPE:

  • move down to a lower altitude immediately
  • take nifedipine
  • give bottled oxygen, if available

The medication nifedipine helps to reduce chest tightness and ease breathing.

You should go to hospital as soon as possible for follow-up treatment.

If you've had HAPE, you can register with the International HAPE Database to help develop new treatments for the condition.

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