Altitude Illness while Trekking in Nepal

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Altitude illness occurs due to changed pressure and oxygen levels. As the altitude increases the pressure levels drop and as a result oxygen levels drop accordingly. Altitude illness may kick in when reaching 3,000 meters and above as a result of the body being unable to adapt to the new pressure and oxygen levels.

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Acclimatization while Trekking in Nepal

Ascending slowly will help your body to adjust to decreased pressure and oxygen levels. This is normally known as ‘Acclimatization’. Two infamous trekking routes in Nepal – the Everest Base Camp trek and trek to Annapurna Circuit, both reach altitude above 5,000 m. At such an  altitude oxygen levels will be approximately 50% of the normal levels. Both treks therefore normally include one or two ‘acclimatization days’ where trekkers may go for a hike or two but will return to rest place at a similar altitude level and rest for the night.

For people summiting Everest, Lhotse and other +8,000 meters mountains, as soon as reaching above 8,000 meter they enter the ‘death zone’ as oxygen levels have decreased to as much as 1/3 compared with sea levels. At such altitudes, the body is normally not able to adapt to a sustainable level and climbers are only advised to be there for a limited amount of time.

Symptoms of Altitude Sickness

While altitude illness may have severe consequences it should not be viewed as dangerous as long as proper acclimatization is made. Symptoms of altitude illness normally include headache plus one or more of the following symptoms:

  • Headache/nausea
  • Tiredness
  • Sleeplessness
  • Social withdrawel
  • Swelling extremities

When trekking or climbing above 3,000 m it is important to be on the watch out for the above symptoms. Should you believe you have any of them it is recommended to not ascend higher, or descend to lower altitude levels.


The best ways to avoid getting altitude illness are:

  • When above 3,000 m do not ascend more than 300-500 m per day
  • Drink enough water as it will speed up the acclimatization process
  • Bring Diamox pills which will can be taken to help your body adapt faster to new altitude levels
  • Do not physically exhaust your body too much – better longer and slower ascends than short and fast. It will help your body to gradually adjust to the new pressure and oxygen levels

For more information about altitude illness please refer to Himalayan Rescue Association who normally also conducts altitude sickness presentations in Namche Bazar on the Everest Base Camp trek and in Manang on the Annapurna Circuit trek.

We hope the above was useful. Check out more tours to Nepal here. If any feedback or comments please do not hesitate to comment below.

More information:
Best time to trek to Everest Base Camp
How long does Everest Base Camp trek take
How to get to Everest Base Camp

Published by Erik Jensen, updated on October 19, 2023

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1 COMMENTSWe welcome your questions or comments to this article. Our travel experts will respond within 48 hours.
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    Dolma ToursFeb 24 2023REPLY
    I found your article very informative. Do keep posting such articles! Thank You.