(Latest update: 22/08/2024)
What is Acute Mountain Sickness (AMS) ?
Acute Mountain Sickness (or AMS) is a serious health condition. It’s cause by the lack of body adaptation to the rapid exposure of higher altitudes, where the partial pressure of oxygen is considerably lower *.
The reaction of the human body to altitudes is fairly personal. Generally speaking, though, mountain sickness can show up already at 2500 metres above sea level. If not properly checked and soon approached, AMS can end up with serious consequences and, in extreme cases, be fatal.
Symptoms of AMS
The first symptoms of acute mountain sickness are lack of appetite, nausea, insomnia, headache, dizziness and tiredness. They can be mistaken for a generic indisposition and therefore it’s always important to keep an eye on them. If ignored, these initially unimportant symptoms, can degenerate into an advance state of AMS with hallucinations, blackouts, pulmonary and cerebral edema .
Prevention of AMS: acclimatisation
It seems that being sportive and physically active doesn’t play into account to prevent the acute mountain sickness. Statistics say that not even age or sex influence the personal reaction to altitude.
The main factor for AMS prevention is a slow adaptation to high altitudes. This process is called acclimatisation and it consist in gaining altitude level sufficiently slow for the body to adapt to the lower pressure. The ideal daily height difference is around 300 metres.
“Climb high, sleep low” is the key. A good high mountain hiking habit is to climb even many hundreds metres high every day, but spend the night at a lower altitudes. This method gives the right time to the body to naturally adapt to altitude.
Hydration is the second important factor that helps preventing altitude sickness. As a matter of fact, the first symptoms of AMS are very similar to dehydration. Despite the intense physical activity, it’s quite common to not feel thirst when walking at high altitudes. It’s this lack of water need that often brings the first symptoms to deteriorate into more serious ones. To keep the body hydrated, the minimum suggested quantity of water per day is around 2-3 litres. I talked about it in this guide about what to pack for a few day trekking.
Alcohol and coffee need to be avoided because they dehydrate the body.
What is the cure?
Some medicines help those who want to climb shortly without symptoms. I’ve heard guides not advice these drugs at all because they don’t actually solve the issue and you might find yourself in a worse situation. I don’t know the details of this debate, though.
The only real solution to solve high mountain sickness is to interrupt immediately the climb and descend to lower altitudes.
During tough hikes, like climbing the Kilimanjaro, the guides are prepared to spot any AMS symptoms. But they are not doctors: in case of necessity, their remedy is to simply take you back down, stopping your hike. They often also have a little machine (I don’t know neither the name nor the way it works. If you have any information about it, please let me know!) that clips your finger. With it, twice per day, the guides measure whatever they need to know to make sure you are able to keep on walking high.
Sometimes you can also ask for additional oxygen. But unless you’re climbing the 8.000 metres, I personally think that if you need oxygen to keep walking, it’s actually time for you to stop!
* I’ve often heard of “less oxygen in the air”. Actually oxygen is always at 21% both at the seaside and on top on a high mountain. What’s different is the air pressure that, at high altitudes, “pushes less” the oxygen into the lungs and blood. The consequences is a lower percentage of oxygen in the body.
Disclaimer:
I’m no doctor, nurse or mountain guide.
For better medial information, ask your doctor (or do like millennials and go read Wikipedia).
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Sandra Ans
Interesting post. I have never done hiking, but one day I will because one of my biggest dreams is to visit Machu Picchu. It stands only 2,430 m above sea-level but I have heard a few times, that people are getting sick (AMS) and this trip isn’t so easy as it seems for the first time!
Have you ever had AMS?
The Lady
AMS applies to “high altitude”, which starts around 2400m. I think at the very top of Machu Piccu you might have some of the mild symptoms, like headache, but nothing serious. You are also not going to spend days up there, so AMS is definitely not going to be an issue. And even if you are getting sick, the simple thing to do is come down. I had bad headaches and I can tell you, as soon as you go down, you’ll instantly feel better!