Altitude Sickness Medication Compared: What Works and What Doesn't
The medicines used to prevent and treat altitude sickness, what you can buy without a prescription, and the remedies that aren't worth packing.
Part of the Access Doctor Altitude Sickness Guide.
Key fact: Acetazolamide is the only medicine UK travel health services recommend for preventing altitude sickness. Other medicines treat symptoms or are kept for emergencies, and none replaces a gradual ascent.
Search for altitude sickness tablets and you’ll find prescription medicines, painkillers, herbal remedies and cans of oxygen. Only a few have good evidence behind them, and they do different jobs: some help prevent altitude sickness, some ease symptoms, and some are emergency treatments carried by expedition doctors. For symptoms and what to do, see our guide to altitude sickness.
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Start Altitude Sickness Consultation →Altitude Sickness Medicines at a Glance
| Medicine | What it’s for | Prescription needed? | Good to know |
|---|---|---|---|
| Acetazolamide | Helping to prevent altitude sickness | Yes | Helps you acclimatise faster. The preventive medicine recommended in the UK |
| Ibuprofen or paracetamol | Easing altitude headache | No | Treats the headache, not the cause. Don’t use it to push on higher |
| Anti-sickness medicine | Easing nausea and vomiting | Some | Helps you rest and drink while you recover at the same height |
| Dexamethasone | Emergency treatment of severe altitude sickness and HACE | Yes | A steroid. It relieves symptoms but doesn’t help you acclimatise |
| Nifedipine | Emergency treatment of HAPE, and prevention in people who’ve had it | Yes | Specialist use only |
We supply acetazolamide only. Emergency medicines are carried and given by expedition doctors and trek medics.
Medicines to Prevent Altitude Sickness
Acetazolamide
Acetazolamide (also known as Diamox) makes you breathe a little faster and deeper, which is how your body adapts to altitude naturally, so you acclimatise sooner. The usual preventive dose is 125mg twice a day, started 1 to 2 days before you go up. It’s prescription-only and used off-label, because no medicine is licensed in the UK to prevent altitude sickness. See acetazolamide for altitude sickness for the dose, side effects and who can’t take it.
Other medicines tried for prevention
The NHS Specialist Pharmacy Service reviewed the alternatives and found the evidence inconclusive, and side effects a concern, for aspirin, dexamethasone, ibuprofen, iron, magnesium, spironolactone and sumatriptan. Dexamethasone is sometimes used by specialists for people who can’t take acetazolamide, but it doesn’t help acclimatisation, and symptoms can appear suddenly when it’s stopped.
Medicines to Ease Symptoms
Doctors sometimes treat altitude sickness with acetazolamide at a higher dose (250mg twice a day), alongside rest and stopping the ascent. We don’t supply it for treatment, only for prevention. These simple medicines can ease mild symptoms:
- Paracetamol or ibuprofen for headache
- An anti-sickness medicine if nausea stops you eating and drinking
- Rehydration salts if you’ve been vomiting or have diarrhoea
Feeling better on painkillers isn’t the same as being better. If you needed medicine for a headache at altitude, stay at the same height until you feel well without it.
Avoid sleeping tablets and alcohol at altitude, as both can slow your breathing while you sleep.
Emergency Medicines
Severe altitude illness is treated by going down, with oxygen if it’s available. Dexamethasone (for swelling of the brain, HACE) and nifedipine (for fluid on the lungs, HAPE) buy time during the descent; they don’t replace it. On organised treks and expeditions these are carried by the medic or leader, along with oxygen or a portable pressure bag. Ask your operator what they carry before you book.
If you’ve had HACE or HAPE before, see a travel clinic or specialist before your next trip, because you may need a different plan.
What Can You Buy Over the Counter?
No medicine that prevents altitude sickness is sold over the counter in the UK. Acetazolamide always needs a prescription, which a pharmacist prescriber can provide after a consultation. Without a prescription you can buy painkillers, some anti-sickness medicines and rehydration salts, which help with symptoms only.
Be careful buying tablets abroad or from websites that don’t ask about your health: the strength, quality and even the ingredient can’t be relied on.
What Doesn’t Work
- Herbal “altitude” supplements and ginkgo: studies haven’t shown a reliable benefit
- Coca leaves and coca tea: a tradition in the Andes, but not proven to prevent or treat altitude sickness
- Canned oxygen: a few breaths from a small can makes no lasting difference
- Drinking extra water: staying hydrated helps you feel better, but it doesn’t prevent altitude sickness
Which Do You Need?
Low-risk trip
A gradual ascent, or staying below about 2,800m: no preventive medicine, just a sensible itinerary and painkillers in your bag.
Moderate or high-risk trip
A fast ascent, flying straight to altitude, or a previous episode: preventive tablets are worth discussing with a prescriber.
See altitude sickness by destination for popular trips, and how to prevent altitude sickness for the ascent rules. You can request preventive treatment through our altitude sickness tablets service.
Need Preventive Tablets for Your Trip?
Tell us about your trip and your health. A UK pharmacist prescriber checks whether preventive treatment is suitable for you. Approved before 3pm, Mon–Fri? Dispatched the same day.
Start Altitude Sickness Consultation →Frequently Asked Questions
Which altitude sickness tablet works best?
Acetazolamide has the best evidence for preventing altitude sickness and is the medicine UK travel health services recommend. It works by helping your body acclimatise faster. No tablet works as well as going up gradually.
Are there any over-the-counter altitude sickness tablets?
No medicine that prevents altitude sickness is sold over the counter in the UK. You can buy painkillers and some anti-sickness medicines to ease symptoms, but acetazolamide needs a prescription.
Does ibuprofen prevent altitude sickness?
Ibuprofen eases altitude headache, and a few studies suggest it may reduce symptoms, but the NHS Specialist Pharmacy Service considers the evidence inconclusive. It doesn't help your body acclimatise, so it isn't a substitute for a slow ascent or acetazolamide.
Is dexamethasone better than acetazolamide for altitude sickness?
No, they do different jobs. Acetazolamide helps you acclimatise and is used for prevention. Dexamethasone is a steroid that relieves symptoms without helping acclimatisation, so it's mainly kept as an emergency treatment.
Do herbal altitude sickness remedies work?
There's no reliable evidence that ginkgo, coca or herbal altitude supplements prevent or treat altitude sickness. Don't rely on them for a high-risk trip.
What medicines should I pack for a high-altitude trek?
Painkillers such as paracetamol or ibuprofen, an anti-sickness medicine, rehydration salts and, if a prescriber has advised them, preventive tablets. Check what emergency medicines and oxygen your trek operator carries.
References
- NHS Specialist Pharmacy Service. Using medicines for preventing acute mountain sickness. sps.nhs.uk
- NaTHNaC, TravelHealthPro. Altitude illness. travelhealthpro.org.uk
- Luks AM, et al. Wilderness & Environmental Medicine. Wilderness Medical Society clinical practice guidelines for the prevention, diagnosis and treatment of acute altitude illness: 2024 update. journals.sagepub.com
- NHS. Altitude sickness. nhs.uk
- Electronic Medicines Compendium. Acetazolamide 250mg tablets: Summary of Product Characteristics. medicines.org.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Prescription medicines require a consultation before they can be dispensed. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.