Signs of High-Altitude Sickness, Treatment and Prevention

Here’s a list of the most common high altitude sicknesses and expedition illnesses. Being aware of high altitude sicknesses and expedition illnesses can mean the difference between life and death on the mountain.

Signs of High-Altitude Sickness, Treatment and Prevention

As the expedition seasons kick off, climbers should refresh themselves on the common signs of high altitude sicknesses and expedition illnesses they may encounter on the mountain. While on a mountain, elevation and the lack of oxygen can make it difficult to comprehend when you’re suffering from the effects of high altitude sickness.

Reading up on the topic before an expedition can help you remember what to do in the event you or a fellow climber are experiencing medical difficulties brought on by these elevation-related illnesses.

What is high altitude sickness?

In general, high altitude sickness covers a variety of illnesses brought on by exposure to high elevations. It is a broad term primarily used to describe Hypoxia, High-Altitude Cerebral Edema (HACE), High-Altitude Pulmonary Edema (HAPE) and Acute Mountain Sickness (AMS).

Persons most likely to suffer from these kinds of illnesses are mountaineers and rescue personnel. These illnesses are serious and can result in death if not properly treated.

For the most part of mountaineering history, these medical conditions have not been widely studied. But in recent years, more scientists have been studying the effects of altitude on athletes and mountaineers. Over a decade ago, a 2006 Nova special covered a research team of doctors, mountaineers and an astronaut led by Dr. Peter Hackett as they ascended Mount Denali in Alaska.

Their goal was to better understand the effects of altitude sickness.

High Altitude Cerebral Edema (HACE)

High-Altitude Cerebral Edema (HACE) is a rare form of altitude sickness. A person affected by HACE will begin to develop fluid around the brain, eventually causing swelling, confusion and possibly death.

HACE is caused by exposure to extreme altitude environments, especially mountains above 8,000 meters (26,247 feet) where oxygen levels are low. Generally, HACE can begin to occur in elevations of just 4,000 meters (13,123 feet) or higher.

Signs of High Altitude Cerebral Edema (HACE)

While a general lack of oxygen can lead to confusion in humans, signs of HACE are more severe and should be taken seriously. Signs of high altitude cerebral edema include:

  • Ataxia – difficulty walking, standing or maneuvering
  • Confusion – inability to think clearly, communicate thoughts or understand others
  • Headache – severe pain throughout the head area
  • Seizures – convulsions
  • Breathing irregularities – rapid breathing or shortness of breath
  • Gastrointestinal discomfort – nausea, vomiting, diarrhea
  • Rapid heart rate

Most HACE cases come about rapidly with just minutes or a couple of hours of warning. However, there are cases where HACE sets in over time. Climbers who experience the following during downtime may be suffering from high altitude cerebral edema.

  • Insomnia – continued sleeplessness, difficulty falling asleep, difficulty staying asleep
  • Sleepiness – constant feeling of being tired, fatigue or drowsiness
  • Insufficient urine production

Treatment for High Altitude Cerebral Edema (HACE)

Most cases of HACE improve after one to three days. This is for mild cases. In the event someone is experiencing severe symptoms of HACE, the only treatments are:

  • Descending to a lower altitude
  • A portable hyperbaric chamber
  • Oxygen therapy
  • Medications


Descending by at least 1,000 meters (3,281 feet) or the continued descent until symptoms improve is the best way to treat HACE. While descending, a person should be given extra oxygen, a process called oxygen therapy. This will increase oxygen levels to the brain and body and improve symptoms.

Portable Hypobaric Chamber

In cases where a climber is incapacitated, a portable hyperbaric chamber bag can be used. Descending alone is inadvisable, as physical exertion increases the symptoms of HACE.

One Man HAPO Chamber to treat high altitude sickness mountaineering

Hyperbaric Chamber | Image Credit: Biswarup Ganguly | License


Certain medications can help with the stabilization of climbers suffering from HACE. Generally, Dexamethasone can be taken at a dose of 8mg once, then 4mg every 6 hours. This medication can be administered orally, intramuscular, or IV routes. Dexamethasone is a steroid used to modify or simulate hormone effects, often to reduce inflammation or for tissue growth and repair.

More specifically, some sources cite a need for the administration of dexamethasone at 10mg intravenously, followed by 4mg intramuscularly every 6 hours.

Acetazolamide is a diuretic and was previously used in one clinical study, but it proved beneficial to the patient. The suggested dosing regimen for Acetazolamide is 250mg by mouth, given twice daily. Acetazolamide helps to relieve fluid retention, which can help with the buildup of fluid around the brain and the insufficient production of urine experienced by many climbers that experience HACE.

Other medications used to treat high altitude cerebral edema include NSAIDs to treat pain, headaches and inflammation.

HACE can equally affect any climber from any age group. While there are alternative treatments for HACE besides descending, these are used to alleviate symptoms temporarily. They should not be used as a replacement for an immediate descent.

How to Prevent High Altitude Cerebral Edema

The prevention of HACE is the same as the prevention of Acute Mountain Sickness. See below under “How to Prevent Acute Mountain Sickness.”

High Altitude Pulmonary Edema (HAPE)

High Altitude Pulmonary Edema, or HAPE, is a serious medical condition that can affect climbers in high altitude environments. A climber experiencing HAPE will have an accumulation of fluid in their lungs. Additionally, they’ll experience symptoms associated with HAPE.

Symptoms of High Altitude Pulmonary Edema (HAPE)

  • Shortness of breath when resting, difficulty breathing
  • Tachypnea – abnormally rapid breathing
  • Tachycardia – a heartbeat rate of more than 100 times per minute
  • Fatigue out of proportion with the amount of exertion undertaken
  • Cyanosis – blue or purple discoloration of the skin, pale skin, blue lips and fingertips…
  • A dry cough
  • Temperature up to 38.5°C (101.3°F) is common
  • Expelling of pinkish foam from the mouth, the sensation of drowning

The last symptom is the most serious and is indicative of the last stages of high altitude pulmonary edema. This is when the lungs fill up with fluid and it begins to seep out through the mouth. This foaming secretion is usually pinkish.

Hape can occur at any altitude above 2,500 meters (8,202 feet) and is more common at higher elevations. On average, one in every 50 climbers on Mount Denali will experience HAPE.

Treatment for High Altitude Pulmonary Edema (HAPE)

The only treatments for HAPE are, for the most part, the same as the treatments for HACE. They include:

  • Immediate descent
  • Oxygen therapy
  • A session in a portable hypobaric chamber
  • Minimizing exertion to slow progression
  • Keeping the victim warm
  • Medications

Descent & Oxygen

Immediate descent is necessary to counteract the symptoms and onset of high altitude pulmonary edema. Descent should be done with the use of supplemental oxygen, 4 to 6 L, and if possible, with a partner.

Portable Hypobaric Chamber

In the event descent isn’t possible, and a portable hypobaric chamber is available, it should be used immediately to slow down the effects of HAPE.


The medications for HAPE are different than those for HACE. Nifedipine (Procardia) can be administered at a dose of 30 mg (sustained-release). Oral nifedipine therapy, 10 mg every 4 hours, has been shown to reduce symptoms.

Be aware, if proper treatment is not rendered in time, the climber will experience death by drowning brought on by the fluid present in the lungs.

How to Prevent High Altitude Pulmonary Edema

The best way to prevent altitude sicknesses is to ascend slowly. If you’re predisposed to HACE or HAPE, do not spend a night over 300-350 meters (984-1,148 feet) higher than the previous night if ascending to altitudes above 2500 meters (8,202 feet).

Medications that lower the pulmonary-arterial blood pressure are effective in the prevention of high-altitude pulmonary edema. Nifedipine, for example, can be administered at a rate of 60mg of a timed-release preparation daily, in 2 or 3 divided doses. PDE-5-esterase inhibitors, like tadalafil at 10 mg by mouth twice a day can also be used.

Dexamethasone at a rate of 8mg orally twice daily can also prevent high-altitude pulmonary edema, only if the regimen is begun at least 24 hours before the ascent to a high altitude.

Acute Mountain Sickness (AMS)

Acute Mountain Sickness (AMS) is the most common form of altitude sickness. If left untreated, it can develop into HACE or HAPE. The latter two are severe forms of Acute Mountain Sickness.

AMS is most common in younger people and occurs when a climber proceeds with a rapid ascent to or above 2,500 meters (8202 feet) without proper acclimatization.

Symptoms of Acute Mountain Sickness

  • Headache, nausea, dizziness
  • Malaise – A general sense of being unwell, often accompanied by fatigue, diffuse pain, or lack of interest in activities.
  • Lassitude – a lack of energy, physical or mental weariness
  • Anorexia – inability to eat, lack of enthusiasm for food, not hungry
  • Insomnia – inability to sleep, difficulty falling asleep, difficulty staying asleep

Treatment for Acute Mountain Sickness

To treat AMS, climbers should cease all further ascents and descend at least 500 meters (1,640 feet). Acetazolamide can be given in dosages of 125 to 250 mg twice a day. In addition to this, analgesics like acetaminophen, NSAIDs, or antiemetics can be given depending on the symptoms present.

In severe cases, acetazolamide and oxygen, 1 to 2 L per minute by nasal cannula, should be considered. Dexamethasone can be an option if evacuation is impossible. A portable hyperbaric chamber can be used if available as well.

How to Prevent Acute Mountain Sickness

The administration of acetazolamide 250mg orally twice a day for the prevention of acute mountain sickness has proved effective in many case studies.

Dexamethasone at a rate of 4mg two or three times a day can be used to prevent acute mountain sickness as well, but should only be given in case of intolerance of acetazolamide.


Hypoxia is a silent killer on the mountain. It is a medical condition that occurs when the tissues in the body are deprived of oxygen. The telltale sign that a climber is suffering from the effects of hypoxia is the presence of noticeable confusion. In many cases, a climber isn’t identified as being affected by hypoxia unless the observer is present for a significant amount of time to see the changes in behavior.

In the beginning stages, a person with hypoxia can seem sure about their actions, only the actions themselves are what is wrong. They just aren’t mentally capable of identifying this.

Historically, hypoxia has been the cause of many deaths on high-altitude climbs. It is believed to have been the cause of Andy Harris’ death during the 1996 Everest Disaster on May 10. An account in Jon Krakauer’s book “Into Thin Air” reports that he was disoriented and confused.

When he went to the South Summit of Everest to assist Rob Hall, he told Rob there was no supplemental oxygen in the cache below, and he seemed sure of this. Then he walked away. Later, it was clearer that he was very confused as there was oxygen at the cache. By then, Harris was too far gone and may have unintentionally walked off the edge of the mountain during the expedition. In this example, he may not have seemed confused to Hall who spent little time with him during the exchange. But other climbers were able to tell afterward.

In the later stages of hypoxia, a climber can become more noticeably unsure of their actions, confused, volatile and uncooperative. This was the case with Lincoln Hall, who survived a day on Everest exposed to the elements after refusing help from Sherpas in what became known as the Miracle on Everest.

Symptoms of Hypoxia

Hypoxia isn’t like HAPE where serious physical signs can be seen. And it isn’t like HACE where the brain swells. However, it does have many of the same symptoms as these two conditions. Thus, it should be taken seriously, as the symptoms can cause a climber to make fatal mistakes and harm themselves or others. The most common signs of hypoxia are:

  • Severe confusion
  • Disorientation
  • Changes in skin color from blue to red or vice versa
  • Shortness of breath
  • Wheezing
  • Uncooperative behavior
  • Aggressivity, violence toward others
  • The inability to grasp one’s surroundings

Treatment for Hypoxia

The only treatment for hypoxia is the immediate descent of the climber to a more manageable elevation and the introduction of oxygen into the patient’s system. Oxygen should be rendered prior to descent, and a climber experiencing hypoxia should not be left alone during descent, so long as the climber isn’t posing a significant threat to the assisting climber.


Hypothermia is when a person’s body temperature drops below 35°C (95°F) due to a cold environment. During hypothermia, their blood cells begin to slowly move away from their extremities to the center of their body mass in an effort to protect the vital organs.

Hypothermia can occur anywhere where the temperatures are cold and/or the victim is not properly dressed for the weather. However, it can also occur on the mountain, and it does a lot.

The 4 Stages of Hypothermia

There are four stages of hypothermia according to Swiss Mountain Medicine. They are:

  • Hypothermia I (Mild): alert, uncontrolled shivering with a temp of 35 – 32°C (95 – 90°F). Shivering is most effective with removal from the cold. Limited exercise may help. Eat and drink.
  • Hypothermia II (Moderate): altered mentation, shivering stops. The person has a temp of 32 – 28°C (90 – 82°F). At this point, the person must be actively warmed because they are unable to warm themselves.
  • Hypothermia III (Severe): unconscious with a temperature of 28 – 24°C (82 – 75°F). Handle the person carefully, as the heart becomes progressively more irritable below 32°C
  • Hypothermia IV: Not breathing with a temperature of <24°C (75°F)

People who experience hypothermia may also be affected by frostbite in their fingers, toes, hands and feet. As the blood moves away from the limbs, it leaves the area susceptible to frostbite.

During the final stages of hypothermia, a person may experience a sensation of warmth all over the body. This is caused by the blood cells rushing back to the extremities as the body prepares for death. This is identifiable when the victim is removing articles of clothing, complaining that they are “hot.” It is important to not allow a person experiencing hypothermia to remove their clothing. They should remain clothed at all times and kept warm.

How to Treat Hypothermia

Treating hypothermia is tricky. Try to rewarm the person slowly. Rewarming a person suffering from hypothermia quickly can result in cold blood reaching the extremities, hindering the process. Make a hypothermia wrap.

Items Needed for a Hypothermia Wrap

Create a hypothermia wrap for the victim. What you will need to create a hypothermia wrap is:

  • A waterproof sheet like a tarp
  • Several sleeping bags
  • Warm items, such as hand and feet warmers, sealed bottles of hot water
  • Rope

How to Make a Hypothermia Wrap

  1. Set down a waterproof sheet like a tarp.
  2. Place a foam mat or other improvised cushioning on top in the center of the tarp.
  3. Remove all wet articles of clothing from the victim if replacements are available.
  4. Place the victim in the sleeping bags and stuff the warm items into the sleeping bag with them. The best locations to place warm water bottles are under the arms, on the chest and on the groin area. Touch the bottles and make sure the contents are not too hot, you don’t want to burn your victim and hurt him more than he/she already is.
  5. Do not leave the victim unattended and try to prevent them from falling asleep.
  6. Then, wrap the victim/sleeping bag in the waterproof sheet like a burrito.
  7. Use the rope to secure the wrap.

Here’s an excellent short video from Greg Friese and Kevin Collopy of Wilderness Medical Associates on how to build a hypothermia wrap quickly.

Below is another in-depth video by Jeffrey from Colorado Mountain Man Survival School, which explains everything you need to know about a hypothermia wrap and how to make it.

Of course, a hypothermia wrap only works if you remember to bring these items with you on an expedition. Sleeping bags, rope and water bottles are standard, just remember to bring a waterproof sheet.

How to Prevent Hypothermia

In conditions where hypothermia is going to happen due to circumstances, it’s very hard to prevent it. But if the circumstances allow, the best way to prevent hypothermia is to keep warm. Do not remove any clothing under extreme weather. Always remember that when your body starts feeling hot, it means your body is preparing itself for death – don’t remove your clothing. Huddle together if you’re with other people.

Snow Blindness (Photokeratitis)

Snow blindness occurs when the glare and reflection of the sun on the white surface of snow gradually causes a person to lose their eyesight. It can be described as overexposure to the sun’s UV rays, and this condition is temporary.

Example of small pupils associated with snow blindness.

Example of small pupils associated with snow blindness.

Snow blindness, or photokeratitis, can occur anywhere snow covers a vast area a person will be traversing in. It isn’t necessarily attributed to just mountains, however, mountaineers who spend long periods of time around snow on an expedition are most susceptible.

Mountaineers and climbers should always pack a pair of snow goggles when climbing. Even though an alpine-style ascent is planned, if there is snow, always pack a pair in the event a delay or accident happens.

Symptoms of Snow Blindness

  • Pain and/or redness in the eyes
  • Blurry vision
  • Tearing, swelling of the eyes
  • A gritty feeling
  • Sensitivity to bright light
  • Headache
  • Perception of seeing halos
  • Small pupils
  • Twitching eyelids
  • With extreme exposure, temporary vision loss may occur
Example of red, irritated, tearing eyes associated with snow blindness.

Example of red, irritated, tearing eyes associated with snow blindness.

Treatment for Snow Blindness

On the mountain, the most effective and only treatment for snow blindness is to leave the outdoor environment and retreat to a tent or a dark space. When the symptoms of snow blindness occur, it’s important to descend to a safe location early, as blindness on descent can be deadly.

How to Prevent Snow Blindness

Preventing snow blindness is as easy as utilizing a quality pair of snow goggles for most of the time spent in exposure to UV rays. Climbers are advised to remove goggles as little as possible.

If you found this article useful, also see our short Lesson 101 on high altitude sickness.



Jensen JD, Vincent AL. High Altitude Cerebral Edema (HACE). National Center for Biotechnology Information. US National Library of Medicine, National Institutes of Health, StatPearls Publishing LLC. Published December 24, 2018. Accessed April 10, 2019.

Bhutia M, Goyal K, Rai A, Kedia S, Kumar N, Mitra R. High altitude cerebral edema with a fatal outcome within 24 h of its onset: Shall acclimatization be made compulsory? National Center for Biotechnology Information | Saudi Journal of Anaesthesia. US National Library of Medicine, National Institutes of Health, Wolters Kluwer — Medknow Publications. Published December 2013. Accessed April 9, 2019.


Staff, Mayo Clinic High-altitude pulmonary edema. Mayo Clinic. Accessed April 10, 2019.


Klocke DL, Decker WW, Stepanek J. Altitude-Related Illnesses. Mayo Clinic Proceedings. Elsevier Inc. Published October 1998. Accessed April 8, 2019. PDF

Hamilton RS, Paton BC. The diagnosis and treatment of hypothermia by mountain rescue teams: a survey. Wilderness and Environmental Medicine Journal. Elsevier Inc. Published February 1996. Accessed April 9, 2019.

Schommer K, MD, Bärtsch P, MD. Basic Medical Advice for Travelers to High Altitudes. National Center for Biotechnology Information. Deutscher Arzte-Verlag GmbH. Published December 2018. Accessed April 10, 2019.

Johnson TS, Rock PB, Fulco CS, Trad LA, Spark RF, Maher JT. Prevention of acute mountain sickness by dexamethasone. National Center for Biotechnology Information. US National Library of Medicine. National Institutes of Health. Published March 15, 1984. Accessed April 08, 2019.

For Hypothermia

Zafren K, MD; Giesbrecht GG, PhD; Danzl DF, MD; Brugger H, MD; Sagalyn EB, MD, MPH; Walpoth B, MD; Weiss EA, MD; Auerbach PS, MD; McIntosh SE, MD, MPH; Némethy M, MD; McDevitt M, DO, MPH; Dow J, MD; Schoene RB, MD; Rodway GW, PhD, APRN; Hackett PH, MD; Bennett PL, PhD; Grissom CK, MD. Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia. Wilderness and Environmental Medicine Journal. Published 2014. Accessed April 07, 2019.

Clover G, MD. Hypothermia Fundamentals and Treatment. Advanced Wilderness Life Support. Accessed April 07, 2019.

Walrath J, MD, FAWM, DiMM. Hypothermia Assessment and Treatment in the Wilderness. Advanced Wilderness Life Support. Accessed April 07, 2019.

For Snow Blindness

Porter D, Pagan-Duran B, MD. What is Photokeratitis — Including Snow Blindness? American Academy of Ophthalmology. Published February 16, 2019. Accessed April 06, 2019.


This article is not a substitute for medical advice. This article was not written by a medical professional. Always consult with a medical professional about medications and dosages prior to starting a pharmaceutical regimen to prevent high altitude sickness or other conditions.

More on BCM

Coronavirus Disease 2019 (COVID-19) Advisories, Prevention, Resources

Dealing With Post-Expedition Depression

Why Climbing Mount Everest Cost Over $65,000

13 responses to “Signs of High-Altitude Sickness, Treatment and Prevention

  1. Pingback: Short Definitions for High-Altitude Sicknesses | Base Camp Magazine·

  2. Pingback: Is the Hillary Step Gone? Everest2017 | Base Camp Magazine·

  3. Pingback: Vanessa O’Brien Thinks the Nanga Parbat Rescue Could Have Climbed Higher to Save Tomasz Mackiewicz | Base Camp Magazine·

  4. Pingback: The 1996 Everest Disaster – The Whole Story | Base Camp Magazine·

  5. Pingback: Book Analysis: “Into Thin Air” by Jon Krakauer | Base Camp Magazine·

  6. Pingback: Everest2017 Marks 21st Anniversary of the 1996 Everest Disaster | Base Camp Magazine·

  7. Pingback: General Mountain Safety Tips for Hikers | Base Camp Magazine·

  8. Pingback: Why Climbing Mount Everest Cost Over $65,000 | Base Camp Magazine·

  9. Pingback: Understanding Avalanche Conditions During Winter Mountaineering | Base Camp Magazine·

  10. Pingback: Recommended Mountaineering Books for Beginners | Base Camp Magazine·

  11. Pingback: Coronavirus Disease 2019 (COVID-19) Advisories, Prevention, Resources | Base Camp Magazine·

  12. Pingback: How to Ride Your First PNW Volcano | Base Camp Magazine·

  13. Pingback: General Hiking Safety Tips for Everyone | Base Camp Magazine·

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.