Altitude illness — what you need to know before you travel

Aug 26
3 min read

Updated: Aug 27

What is altitude illness?

Altitude illness covers a range of problems caused by reduced oxygen at higher elevations (usually above about 2,500 metres / 8,200 ft). The main conditions are:

Acute Mountain Sickness (AMS) — headache, loss of appetite, nausea, vomiting, dizziness, sleep disturbance, fatigue and weakness.
High-altitude cerebral oedema (HACE) — confusion, reduced consciousness and poor coordination (a medical emergency).
High-altitude pulmonary oedema (HAPE) — worsening breathlessness, breathlessness when lying flat, a cough that may become wet or blood-tinged, chest tightness (also a medical emergency).

How to prevent it

The single best prevention is gradual ascent and allowing time for acclimatisation. Practical points:

Avoid rapid gains in sleeping altitude; above about 3,000 m try not to increase sleeping elevation by more than 500 m per day and plan a rest day every 3–4 days.
If you develop symptoms, do not sleep higher than your current altitude — descending is the safest action if symptoms worsen.
If you are flying or driving straight from lowland to high altitude, build rest days into your itinerary to average your ascent rate to under ~500 m per day where possible.
Always travel with an experienced guide for remote high-altitude treks and ensure your travel insurance covers emergency evacuation (helicopter) and the maximum altitude you plan to reach.

Medicines used to reduce risk

Medicines may be used in addition to gradual ascent for people at moderate-to-high risk — they are not a substitute for slow ascent.

Acetazolamide (Diamox®) is the preferred preventative medication. The commonly recommended dose is 125 mg twice daily, started one day before ascent and continued for at least two days after reaching the highest altitude. Side effects that this medication can cause are (increased urine, pins and needles, nausea, altered taste).
Important cautions: acetazolamide is contraindicated in pregnancy (especially the first trimester) and in people with a history of severe sulfonamide allergy. Discuss your medical history with a clinician before using.

Who’s at higher risk?

Risk increases with faster ascents, prior history of altitude illness, and certain types of itineraries such as quick ascents of very high peaks (e.g., short climbs of Kilimanjaro). If you fall into a moderate or high risk group, discuss preventive measures with a travel clinic or healthcare professional.

When to seek urgent help

HACE and HAPE are life-threatening. If someone develops confusion, loss of coordination, severe breathlessness, coughing up blood-tinged sputum, or a severe worsening of symptoms — descend immediately and seek urgent medical evacuation. Never leave an affected person alone.

Practical tips from your local pharmacy

Pack paracetamol/ibuprofen for headache and oral rehydration/anti-nausea remedies you normally tolerate (speak to us before taking other medicines).
Consider a trial of acetazolamide with clinical supervision if you’re in a moderate-to-high risk group — we can discuss suitability and side-effects

Need travel advice or a clinic appointment?

If you’re planning a trip to altitudes above ~2,500 m (or you’ll be flying straight into a high-altitude location), book a travel consultation at Pulteney Pharmacy. We can:

Review your medical history and any medications,
Advise on whether acetazolamide is appropriate, and
Help with travel prescriptions, vaccination checks and practical travel health supplies.

Disclaimer: This blog is for general information only — it doesn’t replace personalised medical advice. For individual recommendations, especially if you’re pregnant, have chronic medical conditions, or have had severe reactions to medicines in the past, speak to a clinician.

Source: TravelHealthPro — Altitude illness (travelhealthpro.org.uk/disease/12/altitude-illness)

Wilderness Medicine Society Risk categories for Acute Mountain Sickness

Risk category	Description
Low	Individuals with no prior history of altitude illness and ascending to ≤ 2,800m. Individuals taking ≥ 2 days to arrive at 2,500-3,000m with subsequent increases in sleeping elevation < 500m per day and an extra day for acclimatisation every 1,000m.
Moderate	Individuals with a history of AMS ascending to 2,500-2,800m in one day. Individuals with no history of AMS ascending to > 2,800m in one day. All individuals ascending > 500 m/day (in sleeping elevation) at altitudes above 3,000m but with an extra day for acclimatisation every 1,000m.
High	Individuals with a history of AMS ascending to > 2,800m in one day. All individuals with a history of HACE or HAPE. All individuals ascending to > 3,500m in one day. All individuals ascending > 500 m/day (in sleeping elevation) above 3,000m without extra days for acclimatisation. Very rapid ascents (e.g. < 7 day ascents of Mt. Kilimanjaro).