A practical guide to altitude sickness in South America

Altitude sickness might not be something you’ve had to contend with on many previous trips, but it’s pretty much part and parcel of any adventure through Bolivia, Chile, Colombia, Ecuador, or Peru. In fact, many of South America’s premier tourist destinations, like Cusco, Lake Titicaca, and La Paz, rise well above 2,500m (the typical threshold for altitude sickness).

I wrote an incredibly detailed post on preventing and treating Acute Mountain Sickness and High-Altitude Cerebral/Pulmonary Oedema when trekking at elevation, but it’s also important to acknowledge that altitude sickness and its various symptoms can affect visitors to South America even if they never set foot in the mountains. I’ve spent nearly 6 months travelling South America, plus done all the scientific research for you— here’s everything you need to know about altitude sickness and how to keep it from impacting your trip.

If you’re planning on trekking in South America (or anywhere else at high elevation), check out my comprehensive post on prevention and treatment.

What is altitude sickness?

Decreased barometric pressure at high elevation, which in turn decreases the availability of oxygen in the air, triggers a host of altitude-related physiological responses to occur in our bodies. In plain English: there’s less oxygen in the air at high altitudes, which can lead to a number of unpleasant symptoms. Minor altitude sickness can occur anywhere above 2,500m, but the higher you get, the higher the risk of developing more serious symptoms.

“Altitude sickness” is actually a broad term for 3 specific medical conditions that occur at high altitudes. The primary one you need to worry about in the city or during general day trips is Acute Mountain Sickness (AMS). 

Types of altitude sickness

• Acute Mountain Sickness (AMS): a common but typically minor condition that includes a headache and other symptoms of fatigue or nausea 
• High-altitude Cerebral Oedema (HACE): commonly referred to as “brain swelling”, this is a life-threatening progression of untreated AMS, but usually only occurs at extreme elevation
• High-altitude Pulmonary Oedema (HAPE): also a life-threatening condition characterised by fluid accumulation in the lungs, but usually only occurs at extreme elevation

Just to reiterate: if you’re sticking to the cities and the main tourist attractions of South America, you might experience minor symptoms of AMS, but thankfully the chance of serious complications is pretty low. If you’re doing some high altitude trekking, though, you definitely need to read my other post on altitude sickness, which includes heaps more detail about prevention and treatment of severe AMS, HACE, and HAPE.

What does it feel like to be at high altitude?

For the first few days in Cusco and La Paz, the cities where I personally felt most affected by altitude during my first trip to South America, I was a bit lightheaded if I stood too quickly, my stomach felt unsettled after meals, and I struggled to walk up stairs without panting — basically, I just felt really unfit. These are all totally normal physiological responses to arriving at altitude, and they passed as soon as my body acclimatised. You can probably expect similar symptoms in your first few days at altitude, but don’t fret, none of these things mean you are actually experiencing altitude sickness.

According to recent research, only about 17% percentage of travellers to 3,400m (e.g. Cusco, Peru) will experience severe altitude sickness. In milder cases, AMS is not too dissimilar to a bad hangover— expect a headache, feelings of dizziness or nauseous, difficulty eating, and just general exhaustion. In worse cases, you might experience vomiting and diarrhoea. Although it’s not necessarily the norm, altitude sickness can even interrupt your travel plans, so you should aim to recognise AMS early and take appropriate preventative/treatment steps (discussed later in this post). 

The important thing is just to take it easy for a few days when you arrive at altitude and give your body time to adjust. This means it’s probably not a great idea to jump off the bus in Cusco and go for a hike immediately, nor is it a good idea to sign up for an active day tour of Lake Titicaca if you aren’t fully acclimatised. Keep this in mind when you’re planning your trip— allowing a few days to relax and explore the city at a slower pace before jumping into all the adventure will help you avoid (or at least minimise the risk of) altitude sickness.

Normal responses to altitude

• Decreased “fitness”
• Shortness of breath during activity
• Minor lightheadedness
• Periodic breathing (intermittent periods of sleep apnoea, where you stop breathing and wake yourself up— everyone will experience this above their own altitude “threshold” and it is completely unrelated to any altitude sickness, although it can be a bit alarming if you aren’t aware of it!)
• Frequent need to pee

Symptoms of altitude sickness

• Headache (this is the hallmark of AMS— if you don’t have a headache, you are probably just experiencing a normal response to the altitude)
• Upset stomach
• Loss of appetite 
• Fatigue or lethargy
• Light-headedness or dizziness
• Insomnia 
• Nausea
• Vomiting 

Will I get altitude sickness?

There are several risk factors associated with developing altitude sickness, but it’s really interesting to note that physical fitness actually has nothing to do with it— you can be the fittest person in the world, but it doesn’t mean you’ll be more prepared for altitude than anyone else. Regardless of fitness, it’s important to consider the risk factors for altitude sickness and take steps to prevent it on your trip.

Risk factors for altitude sickness

Elevation

It goes without saying that the higher a city is in elevation, the higher your chance of developing altitude sickness— about 34% of travellers who ascend above 5,000m will develop AMS. Check out the elevation of some popular destinations in South America below.

Rate of ascent

Flying from Lima to Cusco or La Paz represents an ascent of about 3,500m in just a few hours, which can often trigger altitude sickness.

Acclimatisation

If you haven’t properly acclimatised to the altitude before doing physical activity (e.g. hiking the Inca Trail on your first day at elevation), you’ll be at a greater risk of developing altitude sickness.

Individual predisposition

Unfortunately, some people are just more prone to altitude sickness than others, but this is something you won’t know until you’ve actually travelled to high altitudes.

History of AMS, HACE, or HAPE

If you’ve had altitude sickness before, you’re as much as 12x more likely to develop it again (but it’s still not a guarantee).

*So what does this mean for you? 

The individual risk of altitude sickness depends on your itinerary and on your own susceptibility— no two people will experience the same symptoms at the same time in the same way, and you just won’t know how your body is going to react until you’re actually there. Which means it’s best to be prepared!

Elevation of popular destinations

So many travellers are worried about altitude sickness at Machu Picchu, but the ancient citadel actually sits below 2,500m (at 2,430m), so it’s extremely unlikely that you’ll feel the elevation at all! Here are some popular destinations in South America where you do need to consider the altitude:

• Potosí, Bolivia 4090m
• The Altiplano, Bolivia, Chile & Peru up to 4,000m
• Copacabana, Bolivia (Lake Titicaca) 3,840m
• Puno, Peru (Lake Titicaca) 3,820m
• La Paz, Bolivia 3,690m
• Salar de Uyuni, Bolivia 3,665m
• Cusco, Peru 3,400m
• Papallacta, Ecuador 3,300m
• Huaraz, Peru 3,050m
• Ipiales, Colombia 2,900m
• Quito, Ecuador 2,850m
• Bogotá, Colombia 2,640m

How can I avoid getting altitude sickness?

There are a few simple, common-sense ways to prevent serious altitude sickness from interfering with your trip or leaving you sick in bed. Some of these need to be considered at the trip planning stage (such as adding extra days to your itinerary), but there are also some simple things you can do on the trip to help keep altitude sickness at bay.

Tips for preventing altitude sickness

Ascend gradually

Arrange your itinerary in such a way that you are starting in lower elevation cities and working your way towards higher elevation destinations (e.g. Lima to Arequipa to Cusco to Lake Titicaca). This will help you get used to the altitude slowly and minimise the shock to your system.

Acclimatise

Leave a few free days at the start of your itinerary where you can just bum around town and get a feel for the altitude. This will help your body acclimatise before you go any higher in elevation.

Take it easy

It’s important to know your own limits and listen to your body, because you absolutely do not want to ruin your trip by developing severe altitude sickness. Rest often, especially during those first few days, and don’t be surprised when you can’t move at your normal pace. It gets better with time!

Eat a carb-heavy diet 

Especially for those who are experiencing some stomach upset, it’s important to eat lots of carbs while keeping fats to a minimum. Not only are carb-y foods (like potatoes, pasta, rice, bread, and fruit) easier for your body to digest and therefore less likely to cause indigestion, there is also limited evidence to suggest that these foods can help reduce the symptoms of altitude sickness.

Keep hydrated

Drinking lots of water doesn’t do anything to help prevent altitude sickness per say— but many symptoms that mimic altitude sickness (e.g. dizziness) are actually related to dehydration. As a result of the altitude, we also tend to pee more frequently and lose more liquids to sweat evaporation than usual, so it’s extra important to stay hydrated.

Avoid alcohol

Sadly, alcohol can exacerbate symptoms of altitude sickness, so it’s best to skip the beers and pisco sours, at least for your first few days at elevation.

Chew coca leaves

Andean natives have been using coca for more than 3,000 years to alleviate symptoms related to altitude, and bags of coca leaves, coca tea, and even coca candy are now ubiquitous in all of South America’s high-altitude cities. There’s no concrete scientific evidence to suggest that coca leaves are an effective prevention strategy for altitude sickness, but they absolutely help manage the symptoms!

Take Acetazolamide

There is a considerable amount of scientific evidence to support the use of Acetazolamide (Diamox) for preventing altitude sickness. If you’re travelling to very high elevations or are particularly worried about AMS, your doctor might prescribe this respiratory stimulate to aid in your acclimatisation. You can read more about it in this post: HIGH-ALTITUDE TREKKING: A COMPLETE GUIDE TO PREVENTING & TREATING ALTITUDE SICKNESS IN THE MOUNTAINS

Other resources

HIGH-ALTITUDE TREKKING: A COMPLETE GUIDE TO PREVENTING & TREATING ALTITUDE SICKNESS IN THE MOUNTAINS

If you are itching to trawl through the evidence yourself, here are some good scientific papers and reputable websites to get you started.

Altitude.org 

Biondich AS, Joslin JD. Coca: High altitude remedy of the ancient Incas. Wilderness & Environmental Medicine. 2015;26(4):567-71. 

Luks AM, McIntosh SE, Grissom CK, Auerbach PS, Rodway GW, Schoene RB, Zafren K, Hackett PH. Wilderness Medical Society consensus guidelines for the prevention and treatment of acute altitude illness. Wilderness & Environmental Medicine. 2010;21(2):146-55. 

Luks AM, Swenson ER, Bärtsch P. Acute high-altitude sickness. European Respiratory Review. 2017;26(143):160096. 

Mehta SR, Chawla A, Kashyap AS. Acute mountain sickness, high altitude cerebral oedema, high altitude pulmonary oedema: The current concepts. Medical Journal, Armed Forces India. 2008;64(2):149. 

Parise I. Travelling safely to places at high altitude: Understanding and preventing altitude illness. Australian Family Physician. 2017;46(6):380.  

Richalet JP, Larmignat P, Poitrine E, Letournel M, Canouï-Poitrine F. Physiological risk factors for severe high-altitude illness: a prospective cohort study. American Journal of Respiratory and Critical Care Medicine. 2012;185(2):192-8.

Roach RC, Hackett PH, Oelz O, Bärtsch P, Luks AM, MacInnis MJ, Baillie JK, Lake Louise AMS Score Consensus Committee. The 2018 Lake Louise acute mountain sickness score. High Altitude Medicine & Biology. 2018;19(1):4-6. 

Vardy J, Vardy J, Judge K. Acute mountain sickness and ascent rates in trekkers above 2500 m in the Nepali Himalaya. Aviation, Space, and Environmental Medicine. 2006;77(7):742-4.

* Just a quick disclaimer that I am not a medical doctor, but I do have a PhD in the medical sciences— I conducted a review of the existing literature and all of the information provided here about altitude sickness is directly from peer-reviewed medical journals. Still, you should consult with a doctor about your specific trip and medical history before taking any medications.