How to Prevent Altitude Sickness When Traveling

rainbow mountain peru

Thinking about visiting a high altitude destination or planning an epic hike across some high altitude peaks? We’ll help you out with your planning checklist: 

  • break in your hiking boots
  • map out your itinerary carefully 
  • prepare for altitude sickness 

Wait—what? If you’re wondering what altitude sickness is and how you can prevent it, this guide is for you. Altitude sickness is quite common for adventurers exploring peaks and terrain above 8,000 feet (~2,400 meters). The key to managing it? Prevention and acclimation. 

What is high altitude?

Expert mountaineers generally split “high altitude” into three camps: 

  • High—areas between 8,000 – 12,000 feet 
  • Very high—areas between 12,000 – 18,000 feet 
  • Extremely high—areas above 18,000 feet 

If you’re going to be spending 2 or more days in an area where the elevation is over 8,000 feet, it’s a good idea to be thinking about altitude sickness. 

What causes altitude sickness?

Altitude sickness is an “illness” that occurs when your body has trouble adjusting to high elevations. Quick science lesson: the oxygen concentration in the air at sea level is about 21% and the barometric sea level pressure is around 760 mmHg. As you gain altitude, the oxygen concentration stays about the same, but the barometric pressure is reduced, so you get less oxygen molecules per breath. 

In other words? You have to take more breaths to get the same levels of oxygen, making physical activity more difficult and increasing your risk for high altitude illness. It’s best to prepare ahead of time not only to protect yourself and your physical health, but to ensure that you’re not stuck in a hotel room with a migraine instead of out exploring!  

What is acclimatization?

Acclimatization is the main way to prevent altitude sickness! It’s a process that allows your body to adjust to higher elevations, or other environmental changes. Typically, this is—or should be, at least!—a gradual process that helps you perform well and stay healthy. 

If you don’t allow for adequate high altitude acclimatization, more dangerous forms of altitude illness become more likely. 

Symptoms to watch out for

When adventuring at higher elevations, it’s important to watch out for high altitude sickness as acclimate from a lower elevation.  If you experience any, it’s a sign to slow down and adjust before proceeding further. 

Mild symptoms typically resolve on their own by staying at a lower elevation level for a day or so. If moderate or severe symptoms present themselves, you should make every effort to descend at least 1,000 feet if possible and get medical help.

Mild symptoms 

  • Headaches
  • Tiredness or fatigue 
  • Dizziness or light-headedness
  • Loss of appetite 
  • Nausea
  • Shortness of breath 
  • Trouble sleeping 

Moderate symptoms 

  • Nausea and vomiting 
  • Severe headache 
  • Limited coordination 
  • Extreme fatigue 
  • Shortness of breath 

Severe symptoms 

  • Reduced mental capabilities: confusion, hallucinations, etc. 
  • Inability to walk or move normally 
  • Extreme trouble breathing

What happens to your body if it doesn’t acclimate?

If you don’t give yourself time to acclimate as you gain altitude, there are several forms of altitude sicknesses that can occur, with varying degrees of severity. 

Acute mountain sickness (AMS) 

  • What is acute mountain sickness? Acute mountain sickness (AMS) is common when climbing, hiking, skiing or just traveling at high elevations (8,000+ feet). It’s caused by reduced air pressure and lower oxygen levels. 
  • What are the symptoms of AMS? Mild AMS includes headaches, tiredness, dizziness, loss of appetite and/or nausea.
  • How do you treat or prevent AMS? The best way to prevent any kind of AMS is by ascending gradually and giving yourself recovery time after new elevation gain. If symptoms present themselves, do not ascend further and rest until they resolve.

Moderate or severe mountain sickness

  • What is moderate or severe mountain sickness? As the name suggests, this is a more extreme form of AMS. Typically, this results from making a rapid ascent or ignoring mild AMS. 
  • What are the symptoms? Severe forms of AMS can include extreme headache, nausea and vomiting, extreme fatigue and trouble breathing, hallucinations, confusion or mental impairment, and decreased coordination.
  • How do you treat or prevent severe AMS? Prevention is the name of the game here—if mild AMS presents itself, stay at your current elevation, stay hydrated, and rest until it resolves.

High Altitude Pulmonary Edema (HAPE)

  • What is HAPE? HAPE is a dangerous condition connected with AMS. It occurs when fluid builds up in the lungs and prevents effective oxygen exchange (something that’s super important at a higher altitude!) 
  • What are the symptoms of HAPE? Signs of HAPE include extreme chest tightness and pain, extreme weakness and shortness of breath, impaired mental behavior (confusion, hallucinations, etc.) and/or a cough that brings up a white, frothy fluid.
  • How do you treat or prevent HAPE? Like other high-altitude sicknesses, HAPE generally occurs from ascending too high too fast. If you or someone in your group presents symptoms of HAPE, you should administer supplemental oxygen immediately, if available, and make a rapid descent to lower altitudes.

High Altitude Cerebral Edema (HACE) 

  • What is HACE? HACE is a super dangerous illness associated with AMS. With HACE, fluid builds up in your skull and causes brain tissue swelling.
  • What are the symptoms of HACE? Symptoms of HACE include impaired thinking/motor skills, hallucinations, memory loss, lack of coordination, migraines and, in some cases, comas.
  • How do you treat or prevent HACE? HACE can be prevented by acclimating to higher altitudes gradually and treating mild and moderate AMS symptoms early. If HACE symptoms occur, you will need to get medical assistance immediately—make an immediate descent and administer more oxygen if possible. 

When do you need to acclimate?

Any adventurer looking to hike, climb or ski in high elevations should be prepared to acclimate first. This is expected when tackling Everest Base Camp or Kilimanjaro, but also during lots of treks in South America, such as the Inca Trail or a Cordillera Huayhuash trek.

Altitude sickness can affect anyone—regardless of age, gender, or fitness level.  The quicker you gain elevation and the higher you climb, the more at risk you are of developing altitude illness. Here are a few scenarios where you should definitely be acclimating: 

  • Sleeping or climbing at 10,000+ feet. Everyone’s “acclimatization line” (the point at which you start developing altitude illness) is different, but anyone traveling or climbing somewhere over 10,000 feet is at risk and should prepare accordingly.
  • If you live at low elevations. If you live at or near sea level (below 2,000 feet), you will likely need more time to adjust to the high altitude. 
  • Pre-existing conditions. Genetics can play a role in your acclimatization line and how easily you can acclimate. In addition, if you have a pre-existing condition such as low/high red blood cells, cardiac or pulmonary conditions, you’re more at risk for altitude sickness.

Of course, before attempting any kind of adventure, it’s always a good idea to check with your doctor and get the appropriate information and advice based on your body and situation.

How to acclimate to high altitude

Remember: adventures at higher altitudes don’t need to be dangerous, they just require careful planning and preparation (something we’re here to help with on Explorer Chick trips!). When planning your trip, here are some ways you can acclimate to high altitude destinations.

  • Drink lots of water! Drinking water helps your body absorb oxygen. Plus, many symptoms of altitude sickness mimic dehydration, so it’s a double-whammy if you’re experiencing both. 
  • Get enough sleep. Sleep is essential for recovery (and jet lag!). Just keep in mind that if you’re already experiencing altitude illness, some light activity can be better than a nap, since breathing rates decrease during sleep (which can make symptoms worse).
  • Avoid alcohol and sleeping pills. These can decrease respiratory rates and make acclimating to higher altitudes harder—stay dry when you’re climbing high! 
  • Eat a high carbohydrate diet. Carbs are easier to digest and require less oxygen for your body to break down, making it easier to stay fueled. 
  • Start small. Keep it light at first to give your body enough time to adjust, especially if you live at a low elevation.
  • Consider taking medicine if needed. Acetazolamide is a prescription drug used for prevention and can help your body adjust to high elevations.
  • Climb high, sleep low. The golden rule of high-altitude climbing! If you climb more than 1,000 feet in a day (above 8,000 feet), plan to make your sleeping elevation slightly lower than the highest altitude you climbed to.
  • Train hard pre-trip. You won’t be able to work at peak fitness levels at high elevation, so training hard pre-trip in nearby mountains will help your body’s ability to adjust!
  • Increase elevation slowly. When climbing and adventuring over 10,000 feet, aim to make altitude increases slowly—1,000 feet per day and a rest day every 3,000 feet (or as needed). 

Read more tips for acclimating to high altitudes from this Rainbow Mountain recap.

How long does it take to acclimate to high altitude

As we’ve mentioned, proper acclimatization happens gradually. For most people, acclimatization from lower elevations takes about 2-3 days. 

If you’re traveling to a high-elevation city, such as Lima or Quito, take it easy for the first few days and don’t plan any high-intensity activities. Be sure to stay hydrated and get plenty of fuel! If you’re planning a high-altitude trek, stay for a few days first in a nearby city to adjust to “base level” before beginning your trek. 

Can you pre-acclimate at home?

Even if you live at a lower altitude, there are ways to pre-acclimate at home! Professional mountaineers, extreme endurance athletes and others train for high-altitude sports at home with the help of exercise masks, special sleeping tents and careful training plans. An exercise mask or Hypoxico tent will imitate the thin air and decreased oxygen content of high altitudes so you can get used to exercising or living in high altitudes before you even arrive. 

Fortunately, for most people, such measures aren’t necessary—booking your adventure through an experienced tour guide will ensure that your trip itinerary includes adequate time for acclimating. 

Ready to Get Hiking?

Want to leave the ascent and descent plans to the professionals and just enjoy the views? Find your perfect trip with Explorer Chick and tackle acclimatization, higher altitudes and amazing scenery safely and alongside a bunch of new friends. 

Rachel Bicha

Rachel Bicha 

Rachel is a hiker, traveler, writer and adventurer. Whether she’s home in New England or halfway across the world, she’s probably just looking for her next mountain to climb. If she’s not traveling or hiking, you can probably find her sketching, taking long walks around town, reading on the porch or perfecting a new recipe. 

Favorite outdoor adventure: solo-hiking through the Dolomites in Italy!

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