When trekking at high altitudes, you need to be aware of the risk of altitude sickness. It can potentially be life-threatening and requires immediate treatment in serious cases. Because the early symptoms are often vague, it’s all the more important to understand exactly what altitude sickness is, which symptoms can occur, and what to do if you start feeling unwell at high elevations.

What is altitude sickness?

Altitude sickness can occur at elevations of around 2,500 metres (8,200 feet) above sea level. This can happen, for example, when travelling to Bolivia, Peru, Ecuador, or Chile, or when hiking Mount Kilimanjaro or in the Himalayas. At altitudes above 4,500 metres (14,800 feet), up to 50% of travellers are affected. However, whether or not someone becomes ill doesn’t depend on physical fitness. The key factors are how fast you ascend and the altitude at which you sleep—also known as your sleeping altitude.

Symptoms of altitude sickness

Early signs of altitude sickness usually appear 6 to 10 hours after arriving at high altitude. These include:

• Headache
• Nausea
• Dizziness
• Loss of appetite
• Sleep disturbances
• Irritability

At this stage, it’s important to stop ascending immediately. The body needs time to adapt to the new conditions. If you continue ascending anyway, more serious symptoms may develop: balance problems, vomiting, light sensitivity, rapid heartbeat, or shortness of breath. At this point, a prompt descent is absolutely essential to prevent severe forms of altitude sickness such as high-altitude cerebral edema (HACE) and/or high-altitude pulmonary edema (HAPE). Both conditions are life-threatening and require immediate medical attention.

Can altitude sickness be prevented?

There are many ways to physically prepare for a hike, but none of them offer reliable protection against altitude sickness. As mentioned: it doesn’t matter whether someone is healthy, athletic, young, or older—anyone can be affected.

The most important preventive measure is proper acclimatisation. This means giving your body enough time to adjust to the lower oxygen levels at high altitude. You can achieve this by ascending slowly and taking regular breaks at certain elevations.

As a general rule of thumb: above 2,500 metres, your sleeping altitude should increase by no more than 300 to 500 metres per day. In addition, plan a rest day for every 1,000 metres of altitude gained, during which no further ascent takes place. Avoid nicotine, alcohol, and sleeping pills, and make sure to stay well hydrated.

If a slow ascent isn’t possible, taking Diamox® (acetazolamide)
as a preventive measure can help reduce the risk of acute altitude sickness. However, the medication can have side effects and should therefore be tested for a few days before your trip. We recommend an individual consultation for personalised advice.

Why altitude sickness is often underestimated

Altitude sickness isn’t something people talk about often, which is why it’s frequently underestimated. While many travellers do notice early symptoms, they don’t associate them with altitude. This is mainly because the symptoms are very non-specific and could have other causes. Headaches, for instance, are one of the most common early signs, but are often attributed to dehydration, lack of sleep, or physical exertion. Nausea, dizziness, and irritability can also be explained away. That’s why many people tend to ignore these warning signs. 

Peer pressure: a hidden danger

Travelling in a group is undeniably more fun. But it also carries a hidden risk: many people try to keep up with the group’s pace—even when it’s too much for them. To suppress symptoms like headaches, some take painkillers. The problem? The discomfort may be masked, but not resolved. In the worst case, you don’t even realise that your condition is worsening and continue ascending when your body urgently needs a break—or even a descent.

What to do if you experience altitude sickness

If you notice early signs of altitude sickness, stop ascending immediately. If your symptoms don’t improve within a few hours, it’s important to descend by at least 500 metres and give your body time to recover. Always descend with a companion. You may take medication for headaches or nausea—but only to ease the descent, not to continue ascending.

Once you’re feeling better, no longer have any medication in your system, and your body has acclimatised, you may resume the ascent—slowly and cautiously. Keep monitoring for warning signs and give your body the time it needs.

Good things take time

Anyone travelling to high-altitude areas should take altitude sickness seriously. With a mindful pace, careful attention to symptoms, and good preparation, many risks can be avoided.

If you’re planning a trip to higher elevations, we recommend a personalised travel consultation with us. Together, we’ll discuss your route, your risk factors, and how you can best protect yourself—so that your altitude adventure will be not only breathtaking but also safe.

References

1. Altitude Sickness – Better Health Channel. (2022). Retrieved June 3, 2022, from https://www.betterhealth.vic.gov.au/health/healthyliving/altitude-sickness
2. Fiore, D., Hall, S., & Shoja, P. (2010). Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment. American Family Physician, 82(9), 1103–1110. Retrieved from https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html
3. Health Risks – HealthyTravel.ch. (2022). Retrieved June 3, 2022, from https://www.healthytravel.ch/health-risks/