Altitude, sickness, also known as acute mountain sickness, is a potentially life-threatening condition which happens when a person is exposed to a high altitude without acclimatizing. It is caused by a decrease in atmospheric pressure, which causes difficulty breathing amongst other things. In severe cases, it may cause fluid to fill up in the lungs and the brain ( pulmonary edema and cerebral edema, respectively), which are potentially life-threatening conditions that will require emergent medical treatment. They are medically referred to as HAPE and HACE, respectively.

Two things are certain to make altitude sickness very likely – ascending faster than 500m per day, and exercising vigorously. Physically fit individuals are not protected – even Olympic athletes get altitude sickness. Altitude sickness happens because there is less oxygen in the air that you breathe at high altitudes.

In the mildest form, symptoms of altitude sickness may start to occur after a height of 2500m above sea-level (8,000 ft). Severe symptoms are caused at heights of 3600m (12,000 ft) and above. 


The symptoms of mild altitude sickness include:

  • headache,
  • nausea,
  • dizziness,
  • tiredness,
  • loss of appetite,
  • upset stomach,
  • feeling unsteady,
  • shortness of breath,
  • increased heart rate,
  • difficulty sleeping, and
  • a feeling of being unwell.

The symptoms of altitude sickness are usually worse at night. If you have mild altitude sickness, you can continue with normal activities. For example, if you are trekking or climbing, you can continue to climb at a steady pace.

Symptoms usually develop between 12 and 24 hours of being at altitude and begin to ease after 48 hours, as the body starts to acclimatize (gets used to the changes in atmospheric pressure).

The symptoms of moderate altitude sickness include:

  • severe headache,
  • nausea and vomiting,
  • increased shortness of breath, and
  • lack of co-ordination (ataxia).

You will find normal activities difficult and symptoms can only be relieved by taking specialist medications and descending to a lower altitude.

The symptoms of severe altitude sickness include:

  • worsening of the symptoms above,
  • persistent, irritable cough,
  • breathlessness (even when resting),
  • bubbling sound in the chest (caused by fluid in the lungs),
  • coughing up pink frothy liquid (sputum),
  • clumsiness and difficulty walking,
  • irrational behaviour,
  • double vision,
  • convulsions (fits),
  • drowsiness, and
  • confusion (caused by swelling of the brain, or fluid on the brain).

Severe altitude sickness is a medical emergency. Someone with severe altitude sickness should immediately descend by at least 600m (2,000 feet).


If your symptoms are severe, stay at your current altitude to let your body adjust.

  • Do not exercise.
  • Drink plenty of fluid (but not alcohol).
  • Do not smoke.
  • Rest until you feel better.

Descending to a lower altitude

If you have altitude sickness, the best treatment is to descend to a lower altitude.

Going down by 300m (1,000 feet) will improve the symptoms of moderate altitude sickness and spending 24 hours at this lower altitude will significantly improve symptoms.

If you have severe altitude sickness, descend immediately by 600m (2,000 feet). You must descend as soon as possible because death can occur if altitude sickness is not treated quickly. Pure (100%) oxygen can be given to improve severe breathing problems caused by altitude sickness.


Painkillers, such as paracetamol or ibuprofen, can be used to treat headaches that are caused by altitude sickness.


Acetazolamide (Diamox) can help reduce the severity of the symptoms of altitude sickness.

Breathing more rapidly enables you to take on board more oxygen, which helps to minimise symptoms such as headache, nausea, and dizziness. This can be particularly helpful at night. If you are a professionally climber, or a person who regularly does frequent climbing to hight altitudes, make sure to have a prescription of acetazolamide from you GP.


Dexamethasone is a strong steroid which decreases inflammation (swelling) of the brain. It is usually taken in 4mg doses three times a day. Symptoms usually improve within about six hours. Dexamethasone can be very useful for treating severe cases of altitude sickness, such as high altitude cerebral edema (HACE).

As with acetazolamide, you should consult your GP before taking dexamethasone.


Nifedipine is often used to treat high blood pressure (hypertension). It can be useful in treating cases of altitude sickness, particularly high altitude pulmonary edema (HAPE). Nifedipine can cause a sudden drop in blood pressure, so if you take it, do not get up too quickly from a lying or sitting position.

Portable hyperbaric chambers

Portable hyperbaric chambers (Gamow or Certec bags) are often used to treat altitude sickness. You are placed inside the chamber and it is pumped full of air, increasing the amount of oxygen inside. The effect of the treatment is equivalent to descending by 2,000m (6,500 feet). Treatment should be continued for at least two hours after which time your symptoms should have improved significantly, allowing you to descend more safely.

Dr. Annie

Physician, mom and wife

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