High-altitude travel can be an exciting part of a holiday, expedition or trekking trip. However, travelling rapidly from sea level to areas above around 2,500 metres can give your body less oxygen than it is used to. This may lead to altitude sickness, also called acute mountain sickness (AMS).
Altitude sickness is usually mild and improves with rest and acclimatisation, but it can occasionally become life-threatening. Planning ahead is important, particularly if your itinerary includes a rapid ascent, sleeping at high altitude or strenuous walking. Murrayfield Pharmacy’s clinical team can assess your plans and discuss whether altitude sickness medicine may be appropriate for you.
What is altitude sickness?
Altitude sickness occurs when the body has not had enough time to adapt to reduced oxygen availability. It is more likely when someone ascends quickly, sleeps at a higher altitude or undertakes strenuous activity soon after arrival. Physical fitness does not guarantee protection, and previous experience at altitude does not mean you cannot develop symptoms on a later trip.
Symptoms of acute mountain sickness commonly include:
- Headache, often with tiredness, dizziness or light-headedness
- Nausea, reduced appetite or vomiting
- Difficulty sleeping or unusual tiredness
- Shortness of breath during activity
- Feeling generally unwell or unable to keep up with your usual activities
Symptoms often begin within several hours of arriving at altitude, particularly after sleeping at a higher level. Mild symptoms should not be ignored or covered up so that you can continue ascending.
Preventing altitude sickness
The most effective prevention is a gradual ascent that allows time for acclimatisation. Where possible, avoid flying or driving directly from low altitude to a high sleeping altitude. Build rest or acclimatisation days into your itinerary, and avoid increasing the altitude at which you sleep too rapidly.
Practical measures include:
- Ascend gradually and plan rest days during the journey
- Avoid further ascent if you develop symptoms
- Keep physical activity gentle for the first day or two at altitude
- Drink normally and regularly, without forcing excessive amounts of fluid
- Avoid alcohol and medicines that cause sedation, especially during the early acclimatisation period
- Eat regular meals, even if your appetite is reduced
- Keep warm and protect yourself from sun exposure and dehydration
There is no reliable way to acclimatise in advance at home. Training and good fitness may help you cope with exertion, but they do not prevent altitude sickness. Sleeping at a lower altitude is generally safer than simply spending the day at a lower level and returning to a high camp to sleep.
Medicines used for altitude sickness
Acetazolamide
Acetazolamide is commonly used to prevent acute mountain sickness in people who are at increased risk or who cannot plan a sufficiently gradual ascent. It works by encouraging changes in breathing and acid-base balance, helping the body adapt to reduced oxygen availability. It is not a substitute for gradual ascent and should not be used to justify ascending despite significant symptoms.
A clinician will decide whether acetazolamide is suitable and advise when to start and how long to continue it, based on your route, sleeping altitudes, medical history and other medicines. It can cause tingling in the fingers, toes or around the mouth, increased urination, altered taste of carbonated drinks, nausea or headache. These effects are often mild, but you should discuss any concerns with a healthcare professional.
Tell the clinician if you have kidney or liver problems, electrolyte disturbances, severe allergies, previous reactions to acetazolamide or other medicines, or if you are pregnant or breastfeeding. A history of a serious reaction to sulfonamide medicines requires particular care. Do not use someone else’s tablets or rely on leftover medication from a previous trip.
Dexamethasone
Dexamethasone is a corticosteroid that may be prescribed in some circumstances to prevent or treat altitude-related illness. It can be useful when acetazolamide is unsuitable or when rapid ascent cannot be avoided, but it has potential side effects and does not help the body acclimatise in the same way. It should only be taken following an individual clinical assessment and clear instructions.
Some travellers may be prescribed an emergency medicine plan for use if symptoms develop and descent is temporarily delayed. The correct treatment depends on the symptoms, altitude, available assistance and the person’s medical history. Medicines should never delay urgent descent or evacuation.
Recognising serious altitude illness
Acute mountain sickness can progress to high-altitude cerebral oedema (HACE), a swelling of the brain, or high-altitude pulmonary oedema (HAPE), a build-up of fluid in the lungs. Both are medical emergencies.
Warning signs of HACE include severe or worsening headache, confusion, unusual behaviour, difficulty walking in a straight line, poor coordination, extreme drowsiness, reduced consciousness or seizures.
Warning signs of HAPE include breathlessness at rest, a persistent cough, chest tightness, blue or grey lips, marked weakness, fast breathing or coughing up frothy or blood-stained sputum. Symptoms may initially resemble a chest infection or severe exhaustion, but deterioration at altitude can be rapid.
If serious symptoms occur, stop ascending and seek emergency help immediately. Descend to a lower altitude as soon as it is safe, preferably with another person. Arrange urgent medical assessment and use oxygen or a portable hyperbaric chamber if these are available and trained support is present. Do not leave someone with suspected HACE or HAPE alone, and do not assume that tablets alone will resolve the problem.
Who should seek advice before travelling?
Anyone planning to sleep at high altitude may benefit from a travel health consultation, particularly if the itinerary involves a rapid ascent, remote trekking or limited access to medical care. An assessment is especially important if you have heart or lung disease, high blood pressure, kidney problems, diabetes, pregnancy, sleep apnoea or a history of altitude sickness.
Bring details of your destinations, the altitude of each overnight stop, your ascent schedule, planned activities and all medicines you take. The clinician can review your risk, discuss prevention, check for relevant interactions and provide clear instructions about what to do if symptoms occur. Allow time before departure so that any prescription can be supplied and understood before you travel.
Book altitude sickness treatment in Edinburgh
For individual advice before high-altitude travel, book an altitude sickness medicines and treatment consultation at Murrayfield Pharmacy, 115 Corstorphine Road, Edinburgh. Our clinical team can help you prepare safely, with no waiting lists.