Learn about symptoms and causes of mountain sickness, self help treatment options, medication and when to seek medical help.

What is mountain sickness?

Mountain sickness, also known as high altitude illness, is a condition which could happen when travelling to areas of high altitude (generally above 2400 metres). The three forms of mountain sickness are:

1. Acute Mountain Sickness (AMS) – most common
2. High Altitude Cerebral Edema (HACE) – involves swelling of the brain 
3. High Altitude Pulmonary Edema (HAPE) - involves fluid buildup in the lungs

What are the possible causes of mountain sickness?

Mountain sickness typically affects people who are not used to high altitudes and occurs when one travels ‘too high too fast’. 

The specific causes of mountain sickness are unclear. As one moves to a greater height, the air pressure decreases and the oxygen level reduces, leading to a lower amount of oxygen that is taken in with each breath. It is suggested that the lower amount of oxygen taken in could affect the body’s ability to function properly. In more severe cases, it could result in fluid buildup in the brain (HACE) or lungs (HAPE).

What are the symptoms of mountain sickness?

The symptoms of mountain sickness include the following:

• Headache
• Tiredness
• Dizziness and light-headedness
• Nausea and vomiting
• Difficulty sleeping

Symptoms that may occur with more severe acute mountain sickness in patient experiencing HACE and HAPE

• Confusion, irritability, unresponsiveness
• Poor control of movement, unclear speech, blurred vision
• Shortness of breath
• Chesty or bloody cough
• Have blue or grey skin, lips, tongue or nails

Symptoms can occur as soon as one hour and as late as 24 hours after arrival at the location of high altitude. They usually resolve in one to two days if there is no further ascent, and do not recur at the same altitude.

What can I do to treat or prevent mountain sickness?

Mountain sickness can be prevented with a medicine called Acetazolamide before reaching a high altitude. It can also be used to reduce symptoms of mountain sickness and improve the ease in breathing . Dexamethasone may also be used to treat the symptoms of mountain sickness and swelling in the brain. These medications are NOT available over the counter and require a doctor’s prescription.

Other useful medications for travelling to areas of high altitudes include motion sickness medication, such as Promethazine or Dimenhydrinate for nausea and vomiting; and Paracetamol or Ibuprofen for headaches. These medications may be purchased without a doctor’s prescription.

When do I need to see a doctor?

Mountain sickness with mild symptoms can be treated without a doctor’s consultation. However, there are times where the condition might be more serious. 

If your condition gets worse or if you experience symptoms of HACE or HAPE (see above), you should see a doctor. 

What else can I do to manage mountain sickness?

Other than using medications to treat the condition, mountain sickness can also be managed by the following methods:

• Rest and acclimatise (adjusting to a different climate):  Avoid activities that require great effort and allow the body to get used to the changes in air pressure and reduced oxygen level when travelling to higher heights.  
• Descend 500 metres to 1000 metres: Usually reverses the symptoms of mountain sickness effectively.
• Providing oxygen supply: Can be given under medical supervision.

The following are some suggestions to prevent mountain sickness from happening again:

• Ascending slowly is reportedly the most effective method to prevent mountain sickness: 
  • Spending some time (days to weeks) or participating in brief climbs at intermediate altitudes (2500 metres to 3000 metres) before ascending to higher altitudes can help with acclimatisation and reduce the concern of mountain sickness.
  • Plan a rest day for every 1000 metres of elevation (at altitudes above 3000 metres)
  • For altitudes above 3000 metres, it is recommended not to sleep at a height of more than 600 metres from the previous night’s altitude.
  • ‘Climb high, sleep low’: Ascending to higher altitudes during the day and returning to a lower altitude to sleep may increase the rate of acclimatisation.
• Avoid sedative medications and alcohol.
• Proper hydration can support the body’s adjustments to high altitudes and may help reduce symptoms of mountain sickness.
• Consuming more carbohydrates (e.g. rice, noodles, bread) is suggested to increase energy reserves to meet the body’s need for more energy at higher altitudes.

Disclaimers

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

 The content above is solely for informational purposes only and is not intended as a substitute for the advice provided by your physician, pharmacist or other healthcare professional. You should not use the information for diagnosing or treating a health problem or disease, or prescribing any medication or other treatment. Always speak with your physician, pharmacist or other healthcare professional before taking any medication or supplement, or adopting any treatment for a health problem.