High Altitude Health Tips

The mountains are among the most beautiful places to visit and we hope to enjoy every bit of the visit. However, these mountains often rest at high altitude and can cause health problems for visitors like you and me – the hikers, trekkers and climbers.
Here, we will discuss the health issues and common injuries that may occur at high altitude. We will also share some tips on how to prevent these injuries, as we all know, prevention is always better than cure.


The information shared here are compiled and reviewed by our Medical Advisor – Dr Shani Tan

Health Issues at High Altitude

Altitudes over 3000m can pose health issues. Problems are related to:
  1. High altitude (reduced amount of oxygen available to the human body)
  2. Cold temperatures and dry air (high altitude places are often cold and dry)
  3. Remote location – we usually have to travel a significant distance from “civilisation” to access these beautiful places.
  4. Pre-existing medical problems may get worse
Our bodies will have to adapt to the reduced oxygen (a process called acclimatisation) and get used to cold dry air. We will experience new sensations and changes in our bodies.
Though generally not life-threatening, these health issues can drastically alter the level of performance during a trek. It is vital and important to look after your body well and keep it in optimal conditions at altitude. If you have pre-existing medical conditions, visit your Family Doctor and Travel Clinic before the trip for specific advice.

Some of the most common effects of altitude exposure on the human body include:

Reduced physical performance: The human body cannot maintain the same physical performance at altitude as they can at sea level, regardless of sea level fitness. With acclimatisation this can improve. Individuals acclimate at different rates.

Psychological Effects: Altitude exposure may result in changes in senses e.g. taste and appetite, mood, and sometimes personality. These effects are directly related to altitude and are common at over 3000m. Some effects occur early and are temporary while others may persist after acclimatization or even for a period of time after descent.

Sleep Disturbances: Altitude exposure will have significant effects on sleep. The most prominent effects are frequent periods of apnea (a temporary pause in breathing) leading to fragmented sleep. Reports of “not being able to sleep” and “being awake half the night” are common and may also contribute to mood changes and daytime tiredness. Changes in time zone due to travel, not being used to sleeping in a sleeping bag or on a sleeping mat or tent may also contribute to poor sleep.

Dehydration: Dehydration is very common. Causes include perspiration/sweating, vomiting (due to altitude illness or gastro-enteritis), increased breathing (due to physical activity and altitude) and diminished thirst sensation. Dehydration decreases physical performance, increases symptoms of altitude illness, and may increase risk of developing cold injuries.

Nutrition: Poor nutrition can severely impact health and energy levels and contribute to illness or injury, decreased performance and poor morale. At high elevations dulled taste sensations (making food undesirable), nausea, or lack of energy can decrease the motivation to prepare or eat meals. Poor eating habits may also lead to constipation, aggravation of hemorrhoids, and undesired weight loss.

These Are Some Ways That You Can Take Care Of Your Health At Altitude:

Acclimatization: If you notice any early-warning symptoms (headache, nausea, sleeping problems, dizziness, general uneasiness), do not ascend to a higher altitude. Consider asking your GP about a medication called Acetazolamide (Diamox). It may be taken prophylactically or as treatment for Altitude Illness. Recommendations for Acetazolamide can be found here. (I will provide a link)

Hydration: Dehydration at high altitudes can be a serious problem, especially while you are acclimatising. Do not assume that you are OK if you are not thirsty. Drink water or tea regularly and aim for about 2-3 litres of liquids each day. Start hydrating adequately a few days prior to the start of the trek and throughout the trek. Practice the discipline of adequate hydration during your pre-trip physical training. Weight yourself before and after a training session to see how much sweat (fluid) you have lost. If you have been sweating a lot and think you have drunk enough fluid and are still lighter at the end of the session, then you haven’t drunk enough. In the tropics it is not uncommon to sweat 1L per hour or more. In cooler temperatures the loss will of course be less.

Keep warm / Stay dry: Extremes of temperature are not uncommon. The temperature can rise or fall in a very short space of time. Ensure that you have the essential layers of warm clothing to prevent the body from catching a chill. Trekking in the day can be hot and causes the body to perspire. Wear clothing that wicks perspiration away from the body and stays dry. Avoid materials such as cotton that does not wick and stays soggy. Examples of good materials are polypropylene, polyester and merino wool (which stays warm even when wet). Have a good layering system of several thin and medium layers instead of one thick layer so that you can adjust your clothing to stay comfortable, avoid excessive sweating and making all your clothes sweaty. When you stop to rest, and if your layer is super wet, change out to a dry layer. If your base layer is not wet, put on a layer to keep warm when in-active.

Boost up the immune system: Take multi-vitamins or Vitamin C, eat lots of fruits and vegetables if possible. Visit the Travel clinic in good time before the trip and get the recommended immunisations.

Keep the throat moist: Due to the dry and cold air, dry throat and cough is common at altitude. Keep the throat moist by drinking warm water (good to drink honey lemon water), suck on 1 or 2 lozenges, and breathe through the nose if possible (we recognise that some people are mouth breathers. Keep a small Thermos flask with hot water with you at bedtime such that warm water is within reach if you wake up with a dry throat in the middle of the night. Wear a lightweight neck gaiter or bandana if trekking along very dry and dusty trails – cover your nose and mouth and breathe through that if you find dry air and mouth breathing gives you a dry throat.

Eat well: You will need those extra calories to keep warm and give you the energy for the long treks. Even if you do not have an appetite, do try to eat.

Avoid Alcohol and sleeping agents (medication that cause drowsiness): Avoid use of alcohol or sleeping agents. They both suppress breathing and result in lower blood oxygen level in the body.

Get adequate sleep & rest: It is sometimes difficult to sleep at high altitude, try to avoid lying flat on the bed or in a tent. Use your backpack as a back rest so that you rest your upper body slightly elevated.


Understanding the health issues at high altitude, we list three important potential injuries:

1. Altitude Sickness
2. Sun Damage
3. Cold Injuries


As one ascends through the atmosphere, barometric pressure decreases (though the air still contains 21% oxygen) and thus every breath contains fewer and fewer molecules of oxygen. One must work harder to obtain oxygen, by breathing faster and deeper. The body also adapts (acclimatises) at the molecular level for example by making more red blood cells (to carry more oxygen).

Mountain medicine recognizes three altitude regions that reflect the lowered amount of oxygen in the atmosphere:

  • High altitude = 1500–3500m
  • Very high altitude = 3500–5500m
  • Extreme altitude = above 5500m

Travel to each of these altitude regions can lead to medical problems, from the mild symptoms of acute mountain sickness (AMS) to the potentially fatal high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). The higher the altitude, the greater the risks.

Let us understand the various symptoms of Altitude Sickness:

Altitude sickness is a spectrum ranging from mild (AMS) to life threatening (HAPE & HACE)


1. Acute Mountain Sickness (AMS)

Acute mountain sickness (AMS) is the most common response to altitude: it is a collection of signs that your body is becoming ill and has not adapted successfully to a higher altitude.

AMS usually appears 24-48h after arriving at altitude. Mild AMS is common and in most instances, with sensible acclimatisation, will resolve.

However, for your own safety, assume any illness at altitude is AMS. The most common reasons that people fail to descend as soon as they should are bad assumptions. They assume that having AMS is a sign of weakness; that their level of fitness means they should not have AMS; or mistook their symptoms for flu or another illness. Assume AMS first: it happens to healthy strong people, and if it turns out you are indeed sick with something else, descending to a lower altitude will make it easier for your body to heal anyway.

In particular, if you have recently ascended, and you have a headache and any other symptom listed below, you have AMS.

The symptoms of AMS vary for different people:

Headache +

  • Fatigue
  • Loss of appetite / nausea / vomiting
  • Dizziness / light headedness

If you have headache plus any of the other symptoms, you have AMS. Period. No further discussion.

The next 4 symptoms or signs are danger signs!!:

  • Confusion / change of personality
  • Unsteady walking (unable to walk a straight line – also known as ataxic gait)
  • Rattling / crackly breathing, coughing up frothy sputum
  • Extreme fatigue (e.g. unable to get out of sleeping bag or walk)

The last four signs in particular are signs that you are becoming quite ill. You should not wait for the onset of these symptoms before acknowledging you have AMS. They are fairly reliable indicators of the onset of HACE or HAPE. HAPE and HACE if untreated will kill you.


You and your party should keep an eye on each other for signs of AMS. If you suspect of someone suffering from AMS, look out for signs of it worsening. Very sick people can become confused and not realise how sick they are. Loss of appetite is a particularly good sign: anyone who has been walking or climbing at altitude for a day should be hungry for a good meal in the evening.

2. High Altitude Cerebral Edema (HACE)Brain Pic by Joanne (resized)

High Altitude Cerebral Edema (HACE) is the end-stage of AMS (conversely AMS can be thought of as the mild form of HACE). When you suffer “HACE”, your brain swells and stops working properly. HACE can kill within a few hours.

HACE symptoms include a number of signs of failing mental function: confusion, fatigue and unusual behaviour. But the most reliable one is ataxic gait, and you can test it by walking heel to toe along a straight line on the ground. Healthy people can pass this test easily; anyone who has difficulty balancing while they do it may be showing signs of HACE.

HACE is extremely serious, and you may only have a few hours to help someone with HACE. The most important treatment for this is immediate descent, but a person experiencing these symptoms will need significant help. They may need to be carried. Dexamethasone is one drug that can be used to relieve symptoms, but it is just a temporary bridge to give more time for descent. If your trekking party has oxygen, it can be given at 1-2L/min whilst waiting for evacuation and also during evacuation.

3. High Altitude Pulmonary Edema (HAPE)

High Altitude Pulmonary Edema (HAPE) is another severe altitude illness. It sometimes occurs Lung Pic by Joannein conjunction with AMS or HACE, but sometimes not.When you have HAPE, your lungs fill with fluid. Signs include extreme fatigue; breathlessness at rest, cough especially if it is wet (lots of frothy sputum) and has blood in it; rattling or gurgling breath; chest congestion; very fast heart rate; very fast breathing; and blue extremities. A fever is sometimes present. HAPE most commonly sets in at night.

Preventive Measures for Altitude Sickness

These are things that you can do to improve your chances of not getting altitude illness:


  • Keep in good health
  • Get fit, get adequate rest
  • Eat a healthy diet
  • Try not to catch coughs and cold

During Trip

  • Ascend gradually: above 2500m – 3000m altitude; not more than 500m per day and having a rest day every 1000m
  • “Climb high sleep low”
  • Hydrate adequately
  • Eat regular meals
  • Avoid alcohol, smoking
  • Do not take sleeping drugs
  • Learn to recognise early signs and symptoms of altitude illness

Golden Rules that can help you to avoid getting into a severe confrontation with death!

Golden Rule #1
If you feel unwell at altitude, it is altitude illness unless proven otherwise!

Golden Rule #2
Never ascend with symptoms of AMS

Golden Rule #3
If you are getting worse (or have HACE or HAPE), go down at once!



Skin and eyes (cornea) are at risk of sun’s ultraviolet (UV) damage. At high altitude, the UV rays from theLee Peh Gee on Everest sun are more intense because the atmosphere is thinner. Even when it is cloudy, the risk of sunburn is extreme. The main reason for this is that in cool or cloudy conditions many people are unaware that they are still vulnerable to the burning effects of the sun’s UV radiation, so fail to take precautionary sun protection measures.

There is also a risk of wind contributing to a burn, though the wind does not really burn you.  The cooling effects of the wind decrease the perception of heat and burning. In other words, individuals are less likely to seek shade or to protect themselves against the sun, and are more likely to stay exposed to the burning effects of the sun’s UV radiation for longer. Along with being cooling, the wind also has a drying effect on the skin, which may exacerbate the symptoms of sunburn. UV radiation is subdivided into UVA, which penetrates deeper and causes skin aging and UVB which causes sunburn and increased risk of skin cancer.

The human eye is more likely to be damaged by UV rays while skiing or climbing on the slopes in snow-covered areas compared to sitting on the beach. UV rays can cause conditions such as immediate conditions such as snow blindness, and long term effects such as cataracts.

The safest way to enjoy the sun and protect yourself from sunburn is to use a combination of shade, clothing, sunscreen and proper sunglasses.

Ways to protect yourself from the sun

  • Sunscreen: minimum SPF 15, and Broad Spectrum (i.e. covers UVA and UVB). SPF greater than 50A combination of protection from the UVA are not very meaningful. What does SPF really mean? SPF 15 blocks 93% of UVB, SPF 30 blocks 97% and SPF 50 blocks about 98%.
  • Make sure to apply 20-30min before sun exposure and re-apply every 2-3h. Earlier if sweating a lot and wiping your face!
  • Ensure sunscreen is applied generously to all sun exposed skin. Don’t forget ears and back of neck!
  • Don’t forget your lips – there is nothing worse than burnt cracked lips. Use a chapstick with SPF and moisturiser. Test it at home to make sure your lips are not allergic to it. Reapply regularly and after eating.
  • Wear a hat, wide brimmed if possible, protect your scalp, especially those who are balding!
  • Wear long sleeved SPF / UPF rated tops with fold up collars or hoods.
  • Rest under shade or shelter if possible
  • Protect your eyes! All must have 100% UV fliter. Depending on the altitude, and conditions you may need higher rated sunglasses than just those used in the city. Regular shades let in 18-43% sunlight. Category 3 8-18% and Cat 4 3-8%. If you intend to be working on glaciers or snowfields, make sure you have Cat 3 as a minimum Wrap around / side shields will protect your eyes better and are a must in snowy conditions. In windy and very cold conditions, a pair of ski goggles is better protection.


Exposure to cold can produce a variety of injuries that occur as a result of man’s inability to adapt to cold. Therefore, trekking and climbing in cold climates face many risks.

Cold Injuries

Common injury to the fingers due to long exposure in cold environment with little or no protection

Cold injuries are usually due to prolonged exposure to cold temperatures, although they can occur with brief exposure to extremely cold conditions. For heat regulation, our body uses its core (internal organs such as the brain and heart) and its shell (skin, muscles, and limbs). Cold injury to our body’s core is called hypothermia, and cold injury to our body’s shell is called frostbite. Hypothermia and frostbite commonly occur together, but they can occur separately.

What is Hypothermia?

Hypothermia is a decrease in core body temperature from exposure to a cold environment. By definition, if our core temperature is less than 35°C, we have Mild Hypothermia. We need to prevent even mild hypothermia because once a person’s core temperature is 35°C or less, it is hard for them to help themselves and they may become confused and not be able to move properly and will be prone to falls and accidents. A severely hypothermic person may become unconscious and their heart may have very abnormal rhythm or stop altogether.

Hypothermia can even occur at non freezing temperatures if exposure is prolonged. Our body’s natural defenses against the cold are quite limited. Initially, the blood vessels in our skin constrict to reduce heat loss and to keep blood flowing to the vital organs. Shivering (involuntary muscle contraction) and the increased release of hormones result in increased heat production. However, blood vessel constriction and hormone release are usually inadequate to maintain our body’s temperature in cold environments. Individuals who drink alcohol, as well as those who suffer from fatigue, spinal cord injuries, or poor nutrition, are at greater risk for hypothermia.

What is Frostbite?

Frostbite is a localized cold injury to a body part that may occur with or without hypothermia. It is most likely to happen in body parts farthest from the heart and those with large exposed areas. Body parts such as the feet and toes, the hands and fingers, ear, nose are areas that are at greatest risk. In some instances, severe frostbite may require amputation. When human tissue is exposed to near-freezing temperatures, the tissue temperature decreases. As the tissue temperature decreases, it goes through four phases of frostbite. In the first phase, the blood vessels constrict, causing inadequate blood flow and oxygen delivery to the tissues. In the second phase, the tissue temperature drops below sub-zero degree, and ice crystals form in the tissues. Unless the body part is re-warmed, frostbite will progress to the third and fourth phases. In the third phase, fluid leaks from the blood vessels into the damaged tissue. In the fourth phase, the blood vessels clot, resulting in irreversible loss of blood flow to the damaged tissue.

Frostbite symptoms typically start with a sensation of extreme coldness, followed by numbness, and then clumsiness. Superficial frostbite results in numbness and the development of clear, fluid-filled blisters. Deeper frostbite causes deeper blisters filled with purplish fluid (blood filled blisters). In all types of frostbite, the damaged tissue may swell and darken in color after re-warming.

What is Frostnip?
Frostnip is a superficial cooling of tissues without cellular destruction. The initial stages of frostbite are sometimes called frostnip.

How to prevent cold injuries

First, let’s understand what causes cold injuries such as hypothermia and frostbite. Inadequate blood circulation when the ambient temperature is below freezing point leads to frostbite. This can be because the body is constricting circulation to extremities on its own to preserve core temperature and fight hypothermia. In this scenario, the same factors that can lead to hypothermia (extreme cold, inadequate clothing, wet clothes, wind chill) can contribute to frostbite. Poor circulation can also be caused by other factors such as tight clothing or boots, cramped positions, fatigue, certain medications, smoking, alcohol use, or diseases that affect the blood vessels, such as diabetes.

Modern clothing and equipment have decreased the risk for mountain climbers, but frostbite still occurs after accidents, as a result of poor planning, and in severe, unexpected weather. To prevent hypothermia and frostbite in cold conditions, be sure to have proper fitting boots and gloves and change out of wet garments promptly and drink plenty of fluids to avoid dehydration.

Here are some pointers to note:

  • Use a layering system for your clothes. Several thin or medium weight layers is better than a single thick layer. More flexible and allows adjustment of layers depending on temperature.
  • Plan for extra / spare layers of clothing to change out of wet ones, this includes gloves and socks
  • Wear layered gloves; a single thick glove is not adequate except in the mildest conditions. Gloves: wear a thin liner and a thicker outer, making sure that the combination of tow pairs of gloves does not constrict your finger circulation
  • Socks: wear a thin liner and a thicker outer, making sure that the combination of tow pairs of gloves does not constrict your toe circulation or make your boots too tight. Be sure to test these out before the trip.
  • Trekking or climbing boots / shoes must have room for layers (see above point)
  • Be aware of your itinerary / altitude / weather and dress accordingly
  • Stay hydrated, avoid alcoholic drinks, cigarette smoking or recreational drugs
  • Wiggle your toes and fingers regularly to improve circulation
  • Apply moisturiser to fingers to avoid chapped skin

You can click here to read more about the layering concept for attire.

Preexisting Medical Conditions
People with pre-existing medical conditions should speak with a doctor before travelling to high altitudes:

Common conditions such as high blood pressure, asthma and certain lung diseases need a consultation with a doctor who is familiar with high altitude medicine. Their conditions at the very least must be well controlled.

Diabetics must be well controlled. Their condition may become more or less difficult to control depending on their situation and the trip conditions. Those with complications such as nerve damage or eye damage are at risk of further damage. Those with numb fingers and feet are at greater risk of frostbite and other complications.

Certain inherited blood conditions may make high altitude travel more difficult

Pregnant women should seek advice from their Obstetrician especially with regards to availability of adequate care in the event of premature labour. Most advise not travelling above 3000m.


  1. Wilderness Medical Society Guidelines for Hypothermia 2014
  2. CDC advice on Hypothermia https://www.cdc.gov/disasters/winter/staysafe/hypothermia.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fdisasters%2Fwinter%2Fstaysafe%2Ffrostbite.html
  3. The 2018 Lake Louise Acute Mountain Sickness Score Published Online:1 Mar 2018https://doi.org/10.1089/ham.2017.0164
  4. Pregnancy: https://wwwnc.cdc.gov/travel/yellowbook/2018/advising-travelers-with-specific-needs/pregnant-travelers and Advising on travel during pregnancy BMJ2011; 342doi: https://doi.org/10.1136/bmj.d2506
  5. Wilderness Medical Society Guidelines for Hypothermia 2014 https://www.wemjournal.org/article/S1080-6032(14)00283-X/abstract
  6. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Frostbite: 2014 Update: https://www.wemjournal.org/article/S1080-6032(14)00280-4/fulltext
  7. International Society for Mountain Medicine – [ISMM]
  8. Cold Injuries: Hypothermia and Frostbite [CDC]