Good acclimatisation to altitude is one of the most valuable qualities when trekking in the Himalayas and anywhere else where trails take you above 3,000–3,500 metres above sea level. Many trekkers assume that being in good physical shape, strength training or running will prepare them for the expedition — but altitude has a mind of its own.
The body’s ability to function in hypoxic conditions does not depend on fitness level, body type or trekking experience. It is largely individual and unpredictable. That is why it is so important to know how to tell whether your body is coping well with the altitude before symptoms of altitude sickness appear.
What does acclimatisation to altitude involve?
As altitude increases, atmospheric pressure decreases, so each breath of air contains less oxygen. This causes:
- rapid heartbeat
- increased respiratory rate
- greater fatigue
- appetite problems
- a decline in sleep quality
The body must „learn” to function in conditions where there is less oxygen. This process is called acclimatisation and involves, amongst other things:
- an increase in the number of red blood cells
- more efficient use of oxygen by cells
- a change in the heart’s rhythm
- a change in water and electrolyte balance
- improvement in respiratory function
It is during the acclimatisation period that you can tell whether you are predisposed to tolerate high altitudes well.
The key signs that your body is coping well with altitude
1. No headache after reaching a new altitude
A headache is the most common and first sign of AMS (acute mountain sickness). If, after ascending to a higher altitude:
- You don't have a headache
- you can’t feel the throbbing
- you don’t feel any pressure behind your eyes
— this is a sign that the body is coping with a lack of oxygen.
2. Stable breathing and resting heart rate
At high altitudes, your heart beats faster, but if:
- the heart rate is not drastically elevated,
- my breathing becomes calmer with every passing hour,
- you don’t feel as though you’re „running out of breath” whilst resting,
— this means that the adaptation is proceeding as it should.
3. A healthy appetite
Loss of appetite is one of the most common symptoms of AMS. If you’re eating normally or even feeling hungry, these are very good signs. A body that copes well with altitude demands calories because it uses them efficiently.
4. No nausea, loss of appetite or vomiting
Nausea in the mountains is a warning sign. The absence of it means:
- metabolic balance
- the proper functioning of the nervous system
- no cerebral oedema at an early stage
If you don’t have any stomach problems — that’s a big plus for your acclimatisation.
5. A steady supply of energy whilst trekking
Being able to cope well with heights means that you do not:
- sudden drops in energy levels
- „heavy legs”
- shortness of breath on a gentle incline
- excessive sleepiness
Your body is capable of functioning effectively, even when oxygen levels drop.
6. Getting a good night’s sleep at 3,000–4,500 metres
Sleep problems are very common, but if:
- you go to sleep at a reasonable time,
- you don’t wake up feeling short of breath,
- you don’t have nightmares or „altitude snow”,
- you feel refreshed in the morning,
— this is a clear sign that your body is adapting to the altitude.
7. No signs of „drunken balance”
Walking in a straight line is an important neurological test. If:
- you’re walking steadily,
- you don’t feel dizzy,
- you don’t sway from side to side,
— the nervous system does not react abnormally to altitude.
What else indicates a good tolerance for altitude?
A small number of mild headaches
Mild aches and pains are normal, but if they’re minor and go away quickly — that’s great.
Good hydration
An organism that copes well with altitude does not „reject” water, but absorbs it.
Mental balance
At high altitudes, people can become irritable or listless. If you feel calm, that’s a good sign.
Normal body temperature
The absence of a fever is a sign that your metabolism is functioning normally.
Tests and signs that you can aim higher
You can assume that acclimatisation is working if, after climbing 300–500 metres higher:
- you feel much the same as you did the day before
- you don’t have a headache after 1–2 hours
- you don’t feel short of breath when you’re resting
- you have a normal appetite
- the heart rate returns to normal after resting
If all the above points are met, you can carry on with the trek as planned.
And when does that mean you CAN’T stand heights?
As well as the positive signs, it’s worth being aware of the negative ones:
- The headache doesn’t go away after drinking water and resting
- no appetite at any time of day or night
- nausea or vomiting
- insomnia lasting several nights
- heart palpitations
- dizziness
- balance problems
- irritability and confusion
This means that your body is struggling, so you should take a break or go down to a lower altitude.
Is it possible to predict whether someone will cope well with heights?
Unfortunately — no.
A good tolerance for altitude does NOT depend on:
- age
- gender
- training placement
- VO₂ max
- body fat percentage
- muscle strength
Every body reacts differently. The best method is:
- a gradual ascent,
- observation,
- following the acclimatisation guidelines,
- early response to symptoms.
How can you improve your altitude tolerance? (Yes, it is possible!)
1. „Gradual” acclimatisation”
The most effective method — gaining altitude slowly in accordance with the „300–500 m” rule.
2. Climbing higher during the day
Starting with an ascent and then descending speeds up adaptation.
3. Diamox (after consulting a doctor)
It supports adaptation, but does not replace it.
4. Water intake: 3–4 litres a day
Water speeds up metabolic processes.
5. Eating regularly
The body needs energy to function at high altitudes.
6. Avoiding alcohol
Alcohol slows down acclimatisation and dehydrates the body.
Summary
Good altitude tolerance is a combination of biological predisposition, proper acclimatisation, listening to your body and making responsible decisions. You can consider that your body copes well with altitude if:
- you don’t have a headache,
- you breathe calmly,
- you’ve got an appetite,
- you sleep more or less normally,
- you feel a steady flow of energy,
- you don’t have any balance problems,
- there is no nausea.
It is precisely these signals that show your body is capable of functioning in conditions of low oxygen levels, and that you can continue trekking without any worries. But what if you experience any adverse symptoms? The rule is simple: slow down, rest or head downhill. In the mountains, it’s not the person who walks the fastest who wins — it’s the one who listens to their body.
