Altitude Sickness Prevention
Trekking the Himalayas, climbing Kilimanjaro or exploring the Andes? Our pharmacy-led service offers a consultation and, where appropriate, medication to help you travel safely at high elevations.
What is altitude sickness?
Altitude sickness, also known as acute mountain sickness (AMS), occurs when your body struggles to adapt to lower oxygen levels at high elevations. Symptoms usually appear within hours of ascent. In more severe cases it can progress to High Altitude Cerebral Oedema (HACE) or High Altitude Pulmonary Oedema (HAPE), both of which need urgent descent and medical attention.
- Headache
- Nausea or vomiting
- Fatigue and weakness
- Dizziness or light-headedness
- Sleep disturbance
Who this service is for
- Adults aged 18 and over
- Ascending quickly above 2,500–2,800m in a single day
- History of altitude sickness
- Climbing above 3,000m without adequate acclimatisation
- Rapid ascents (e.g. Kilimanjaro in under 7 days)
When it may not be suitable
- Under 18
- Pregnant or breastfeeding
- Severe kidney or liver disease
- Conditions affecting sodium/potassium (e.g. adrenal gland failure)
- Allergy to sulphonamides
- Severe depression, psychiatric illness or uncontrolled epilepsy
- Taking medicines such as lithium, aspirin, sodium bicarbonate, some epilepsy medicines or methenamine
Treatment we can provide
Acetazolamide (Diamox)
How it works: Acetazolamide helps your body acclimatise faster by making you breathe a little deeper and more frequently, which increases oxygen uptake.
How to use
- Typical dose: 125mg twice daily (half a 250mg tablet, morning and evening)
- Start 1–2 days before ascent and continue for at least 2 days after reaching your highest altitude
- Continue treatment until you have acclimatised
- Swallow with water and take with food
This medicine is supplied off-label for altitude sickness — it is not licensed for this purpose in the UK, but its use is supported by national and international guidance. Alcohol can worsen dehydration and altitude symptoms and is best avoided.
Possible side effects
Most people tolerate acetazolamide well. Some may experience increased urination, tingling in fingers or toes, nausea, taste disturbance, headache or drowsiness. Rare but serious side effects include severe allergic reactions, blood disorders or pulmonary oedema — your pharmacist will explain risks during your consultation.
Important
When to seek medical help
The most important treatment is to stop ascending and descend if symptoms worsen. Medication helps but is not a substitute for acclimatisation or descent in severe cases. Descend and seek help immediately if you develop confusion, difficulty walking, severe breathlessness or cough.
Frequently asked questions
Ready when you are
Book your consultation
Speak with our pharmacy team about altitude sickness prevention. We'll review your travel plans and medical history to help you travel prepared.
Information on this page is general guidance only and does not replace personalised medical advice. Suitability of treatment is confirmed at your consultation with our pharmacist.