Your guide to Altitude Acclimatization

by Debra Bouwer

You have longed to get out and climb a mountain or do an extended trek to high altitude and you read about acclimitization. It may all sound very complicated but what is it.

Acclimatization refers to the process that occurs when your body adjusts to a change in your environment, be it cold or heat, lower oxygen levels or extended periods of dark and light. When it comes to mountains, it refers to your body’s adaptation to lower levels of oxygen.

Let us look at a train as an analogy, first mentioned by Stephen Bezruchka. Image a train running along a track and delivering cargo at an end point. After a period, let us say 5 minutes, the train returns to get the next load of cargo and heads back up the track. Now imagine if after 5 minutes the cargo was not all unpacked it would head back down the track, only to return again. The only way to ensure that the cargo was all unpacked would be to make the unloading bay work faster.

This is essentially what happens. Your blood vessels are the railway tracks and your cargo is oxygen. As you ascend in altitude, your body needs to work harder to get all of the oxygen unloaded which means your heart starts to pump faster.

Mt Meru Tanzania

At higher altitudes, (normally above 1500m), the density of oxygen in the atmosphere is decreased which means you get less oxygen. Your heart starts to pump faster to try to get more oxygen to your blood and muscles as it slowly adapts.  Generally speaking, at 2000masl your heart will be about 10% higher than at sea level and at 4500m, about 50% higher. By spending time at each altitude level, your body starts to adjust and your heart rate gradually decreases.  It is for this reason that monitoring your resting heart rate is a good indicator of how well you are acclimatising.

So what can you do to help your body adjust? Simply follow a few steps.


Plan enough time on your trek to acclimatise so e.g. on Kilimanjaro a minimum of 7 days is better than the standard


Allow your body to adjust to a new time zone. It is always a good idea if flying across time zones to give you body time to adjust to the new time zone and also give yourself enough rest before you start climbing

Hiking in Bhutan


There is a reason why there are phrases like “pole pole” which mean slowly slowly. If you walk at a slower pace it helps to keep your heart rate lower and allow you body top get the oxygen it needs.


Drink plenty of water. Water is needed for many bodily functions. Cells need water, water is needed in the blood, and it is needed for keeping our bodily temperature stable and for eliminating waste from our body.

When you hike to higher altitudes, your body will sense the changes and start to make adjustments. Your heart will beat faster and you will breathe more rapidly. Helping your body make those changed to adapt by following the simple steps will go a long way to ensure better acclimatisation and a more enjoyable and safe climb.

Article by Debra Bouwer

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3 thoughts on “Your guide to Altitude Acclimatization

  1. Pingback: How difficult is it to climb Kilimanjaro? | Nomadic Adventures's Blog

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