Some of the world's most majestic peaks and landscapes exist high above sea level. Alpine tundras and snow-capped mountains draw folks in to bask in their beauty, but even a casual sightseeing trip at a high altitude location has its risks. When your body is not accustomed to existing at a high altitude, it can struggle to acclimate to the changes in air pressure and oxygen levels, leading to altitude or mountain sickness which consists of varying degrees of physical and mental symptoms.

A few summers ago, I worked in Rocky Mountain National Park as a horseback tour guide. Most of our tours took place between 8,000-10,000 feet, leaving many folks susceptible to mountain sickness. I witnessed countless people become dizzy or fatigued, while some even fainted, still on their horses, because they drove up to the park from a lower elevation that afternoon and hadn’t acclimatized to the higher altitude yet. It can be surprising and scary for those who haven’t experienced altitude sickness before.

So how do we as hikers and climbers and adventurers prepare for high altitude trips and prevent altitude sickness? There are a number of steps you can take, but first, let's go deeper into what altitude sickness is and how it affects the brain and the body.

What Is Altitude Sickness?

Altitude sickness can begin to occur at around 8,000 feet above sea level, depending on the individual. Some may experience symptoms at lower altitudes (5,000-6,000 feet). Some folks are more at risk than others, though anyone can experience symptoms. Those who have pre-existing medical conditions, specifically those lung and heart-related, like asthma, may be susceptible to experiencing more serious symptoms, as well as pregnant people and those who live at lower elevations closer to sea level. Effects of altitude sickness can become severe at extreme altitudes (greater than 5,500 meters or 18,000 feet). Brief trips above 6,000 meters are possible, though are markedly more dangerous and typically require supplemental oxygen. You enter the “Death Zone” at around 8,000 meters (26,000 feet). The pressure of oxygen at this altitude is not sufficient to sustain human life, and an extended stay will result in extreme symptoms and death. Believe it or not, however, there are a number of superhumans out there who regularly climb 8,000-meter peaks, like Everest, with no supplemental oxygen (not recommended!!).

*If you have a pre-existing condition or are worried about traveling to high elevation, check with your healthcare provider.

Symptoms of altitude sickness can range from mild to severe and can be broken down into three separate categories based on severity. It should be noted that a person could experience symptoms from multiple categories at once, based on the severity of their illness.

Acute Mountain Sickness (AMS)

Acute Mountain Sickness or “AMS” is the most common form of altitude sickness and can include symptoms such as headache, fatigue, lightheadedness, dizziness, nausea, and loss of appetite. AMS usually occurs due to a rapid rate of ascent (driving or hiking to high altitude without allowing acclimatization time). Symptoms usually onset within 1-24 hours of ascending to altitude. Symptoms will usually begin to improve after 24-48 hours as long as you do not continue to ascend in elevation.

High Altitude Pulmonary Edema (HAPE)

The second category of altitude sickness is high altitude pulmonary edema, also known as “HAPE.” HAPE usually occurs 24-72 hours after ascending to altitude and causes fluid to develop in the lungs, resulting in symptoms such as coughing, shortness of breath, and a full or heavy sensation in the chest. This is a serious medical condition. If you experience symptoms of HAPE, descend immediately and seek medical attention.

High Altitude Cerebral Edema (HACE)

The third and most severe category of altitude sickness is high altitude cerebral edema, or “HACE.” Symptoms usually onset between 24-72 hours after ascending and include severe fatigue, weakness, lethargy, inability to walk normally, lack of concentration, confusion, and delirium or delusions. HACE is an emergency medical condition that requires immediate descent and medical care.

*HAPE and HACE can lead to coma or death if left untreated. Altitude sickness is no joke, even in its mildest form and the best way to deal with it is to prevent it.

How to Prevent Altitude Sickness

Here are some tips for preventing altitude sickness:

• Ascend slowly: Gradually increasing elevation over the course of several days or weeks can lessen symptoms and help your body acclimate, whereas a rapid ascent can worsen symptoms. Depending on your trip and the level of exertion you will experience, you may need to plan out your stay with elevation in mind. For hiking at 10,000 feet in Colorado, for instance, a couple of days should suffice for most physically fit and healthy folks to be well enough acclimatized. For climbing in the Himalayas, you are looking at a very slow rate of ascent, with several weeks to months in preparation and acclimatization, and you will likely still experience symptoms.
• Be in good physical shape: If you have a difficult time hiking at lower elevations, you will find hiking at higher elevations nearly impossible. Create a conditioning or training schedule to reach a good base fitness level. Both cardio and strength training are important when conditioning for high-altitude hiking and climbing.
• Hydrate: Drink plenty of water (3-4 liters a day or more depending on exertion levels) and electrolytes in the week leading up to your trip and during your trip. Chugging water alone will not keep you hydrated—you need to replace the essential nutrients your body loses by intaking electrolytes and replenishing foods. Avoid consuming alcohol the first few days of your trip (Yes, that includes the vodka soda you were planning on nursing during the flight).
• Don’t overhydrate: Excessively hydrating can cause an electrolyte imbalance.
• Eat: You need plenty of calories and nutrients on a normal day, but at high altitudes, especially while being active, you need even more to keep your body going. It is recommended that you consume a diet of at least 70% carbohydrates (sorry keto dieters). You will need to substantially increase your calorie intake as well to keep your body going strong.
• Rest: For every 3,000 feet in elevation you climb, build a rest day into your schedule so that your body can recoup and acclimatize.
• “Climb high and sleep low”: If you’re climbing or hiking at a high altitude and are gaining considerable elevation in a day, make sure to come back down and sleep at a lower camp. This will help your body rest and acclimatize.
• Don’t smoke: This should be a given even on a normal day, but avoid smoking, especially during your trip. Avoid sleeping pills as well since they are a respiratory depressant.
• Medication: Bring Tylenol (acetaminophen), Advil (ibuprofen), or Motrin to combat mild symptoms, like headaches. Certain medicines, such as acetazolamide, can be taken preventatively if you have a history of altitude sickness and can be prescribed by a doctor. Dexamethasone, which can be taken in cases of HAPE, can also be taken preventatively in certain situations but can have serious side effects.
• Carry oxygen: At extremely high altitudes you may be required to carry additional oxygen to sustain your body and prevent HAPE and HACE.
• Be self-aware: Know your body and know your limits. Take breaks when you need them. If you are experiencing symptoms, stop, rest, and descend to a lower elevation if you need to.
• Know your susceptibility: If you have struggled with altitude in the past or if you have a pre-existing condition, take appropriate steps to ensure your health and safety.

Visiting higher altitude locations can be fun, safe, and rewarding. It can also be extremely dangerous if you do not prepare or if you ignore the signs of altitude sickness. Regardless of whether you are taking a drive in the mountains a few hours outside of your city or embarking on a mountaineering expedition in a different country, make sure you take the time to acclimatize and listen to your body. If you're heading to high elevation, reach out to a Camping & Hiking expert here on Curated and we can answer your questions and give you free, personalized gear recommendations. Happy hiking!