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How to avoid altitude sickness on your Machu Picchu trek

AMS (acute mountain sickness), also called altitude sickness, is a potentially dangerous illness that can be brought on by exerting yourself at very high altitudes. AMS is not a gradual worsening of the mild symptoms most people notice at high altitudes (mostly headache and shortness of breath) but a dramatic and sudden change which can leave people completely unable to care for themselves or make rational decisions.

Some people notice altitude sickness as early as 2,400 metres (Cuzco is around 3,400 metres) but many start to get symptoms above 3500 metres. The highest passes of the Inca trail are well into this danger zone.

Some people have a much higher altitude tolerance than others, and it is difficult to predict who is at risk and who is not. Generally, though, those who are in good cardiovascular shape fare better than those who are not. Even not-particularly-fit people can avoid AMS by making sure not to strain themselves, and taking proper precautions.

The thing to remember is that it isn’t really the altitude that is the problem, but rather the speed at which you ascend to that height. Simply slowing down substantially at altitude counts for a lot. That means that one of the best ways to avoid contracting AMS is to properly acclimatise yourself.

Recognising AMS

Every Kandoo guide is an expert at diagnosing AMS. This means that following their instructions is the best way to avoid AMS entirely and to get home safely if you do start experiencing symptoms. If they say it is time to come down to a lower elevation, it is time.

AMS Symptoms

The most common symptom of AMS is headache. (Note that headache is also a symptom of dehydration, so stay well hydrated and you’ll be less likely to be misdiagnosed with AMS.) Any headache occurring at an altitude higher than 2400 metres is suspect, but will only give rise to a diagnosis of AMS if it is accompanied by one or more of the following symptoms. If you notice any of these things, notify your guide immediately.

  • Vomiting, nausea or poor appetite
  • Weakness
  • Fatigue or drowsiness
  • Light-headedness or feeling dizzy
  • Insomnia
  • Tingling, numbness or ‘pins and needles’ in the extremities
  • Shortness of breath
  • A persistently high pulse
  • General malaise
  • Oedema (swelling) in the face, hands or feet

Most of the time, these symptoms will improve after a short rest. Nonetheless, they must not be ignored! If you notice any symptoms at all, tell your guide and keep an eye out for other symptoms.

How to avoid AMS

Follow these four steps to minimise your risk of AMS:

1. ‘Walk high and sleep low’
All of Kandoo’s routes are pre-planned to give you the best acclimatisation opportunities, and to allow you to sleep at a lower elevation than you have been at for most of the day.

2. Take it slow
If you are breathing too hard to easily have a conversation, you are putting yourself at risk. Slow things down and take some of the stress off your heart and lungs.

3. Drink far more water than you think you need, or are really comfortable with
Dehydration not only compromises acclimatisation, but it can be confused with AMS as well. Avoid both by drinking 3 litres of water each day at the very least.

If your wee is yellow, you are in danger of dehydration. If it is orange you are already dehydrated. Drink more immediately. Also, bring a wee bottle to bed, unless you enjoy freezing night-time strolls to the loo. 

4. Diamox
Almost everyone has an opinion about whether or not to use Diamox. (Just Google it, you’ll see.) Overall, the research shows that it helps avoid AMS if used correctly. It is though, a prescription drug and you should not decide whether or not to use it without consulting your doctor.

The biggest danger about Diamox is that some people insist upon thinking of it as a cure, or proof against AMS. A few climbers have ignored serious AMS symptoms, thinking themselves protected by Diamox, and come to grief. The simple truth is that if you get symptoms you probably have AMS and you must get to a lower altitude immediately. Diamox doesn’t ‘fix’ AMS, but it does speed up acclimatisation, which can avoid AMS entirely.

To be effective, you need to start taking Diamox a few days before going up to high altitudes. Most experts recommend 125 to 500mg daily. We personally recommend half a 250mg tablet before bed, and another in the morning. (Again, talk to your GP first.)

Diamox does have some side effects, but the common ones are quite mild. It can make your fingers and toes tingle or feel numb. It causes really frequent urination (on top of the 3 litres of water a day, you’ll really notice it). Perhaps the worst is that it makes beer (or anything fizzy) taste awful. The good news is that it all wears off quickly, and if you stop taking Diamox when you get to Machu Picchu, you can enjoy a well-earned beer in Cuzco.

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Rachel Miller

Destination expert

Phone: +44 (0) 1283 499 980

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Rachael Bode

Destination expert

Phone: + 44 (0) 1283 499981

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