Altitude sickness: who gets it, the red flags, and what a consultation can do
Altitude sickness is your body failing to keep pace with thinner air, and it usually shows itself above 2,500 m: on Kilimanjaro, the walk in to Everest Base Camp, the Inca Trail, a first night in La Paz or Leh, and now and then in a high Alpine ski resort. Being fit does not protect you. Going up slowly does. From our pharmacy in Timperley, Altrincham, we run pre-trip altitude consultations for travellers across Trafford and Cheshire and can supply prescription altitude-sickness medication where your itinerary and your health justify it.
Medically reviewed by Muhammad Adnan, Superintendent Pharmacist (GPhC 2073652) · based on NaTHNaC (TravelHealthPro) and NHS guidance · last reviewed 2026-09-16.
Who is likely to get altitude sickness?
Anyone can, and the people caught out most often are the ones who assumed fitness would carry them. The UK travel health service TravelHealthPro is blunt about it: physical fitness does not appear to protect against altitude illness. What matters is how quickly you gain height, how high you sleep each night, how much you exert yourself on arrival, and how your body has behaved up there before. If you had acute mountain sickness on a previous trip, that is the most useful predictor you own. If you have ever had HACE or HAPE, you are in the high-risk group whichever route you pick.
The numbers are worth knowing. Roughly 9 to 25% of unacclimatised people going to 2,000 to 3,000 m develop AMS, rising to 35 to 50% at 3,500 to 4,500 m. Living near sea level, as almost all of us in Trafford and Cheshire do, is itself listed as a risk factor. And some people react below the usual line: a first night at Val Thorens, around 2,300 m, after a straight run from Manchester Airport is enough to give a susceptible skier a thumping head and a rough night, even though serious illness at that height is rare.
What do AMS, HACE and HAPE actually look like?
Three conditions, one spectrum. The mild one is common and manageable. The two severe ones are rare, kill people every year, and share a single treatment: go down.
Acute mountain sickness (AMS)
Arrives 6 to 10 hours after you reach a new height, not on the spot. A headache plus at least one of: no appetite, feeling or being sick, dizziness, unusual tiredness, a broken night. Stay at that altitude, rest, use ordinary painkillers, and it normally clears in 1 to 3 days. Sleep no higher until it has.
High-altitude cerebral oedema (HACE)
Swelling of the brain, usually following AMS that was pushed through. The person becomes confused, clumsy or unsteady on their feet, oddly drowsy or hard to wake. A medical emergency: descend immediately and get urgent help.
High-altitude pulmonary oedema (HAPE)
Fluid in the lungs. Starts as breathlessness on exertion and a dry cough, then breathlessness at rest or lying flat, a wet cough, frothy or blood-stained spit, chest tightness, blue-grey lips. It can strike without AMS first. Descend immediately; oxygen and expedition medicines help but never replace descent.
The rule that saves lives: never sleep higher with any symptom of altitude illness, and if symptoms worsen at a given height or are severe, descend. The NHS suggests dropping around 300 to 1,000 m. Never leave someone with suspected altitude illness alone, and treat any new symptom at altitude as altitude illness until proven otherwise. HACE and HAPE are very rare below 2,800 m and usually appear at least two days after reaching 3,000 to 4,000 m, which is precisely when a group feels acclimatised and wants to push on.
How slowly do you need to go up?
Gradual ascent with rest days is the whole game. The guidance TravelHealthPro and the NHS give is framed around where you sleep, not the highest point you touch during the day:
- Where the route allows, spend a few days below 2,500 m before heading higher.
- Avoid going from below 1,200 m to above 3,500 m in a single day.
- Once above 3,000 m, raise your sleeping altitude by no more than 500 m a day.
- Take a rest day at the same altitude every three or four days.
- If you fly or drive straight in high (La Paz, Cusco, Leh, Lhasa), rest a full day before going anywhere higher, then add extra rest days so the climb averaged over the whole trip stays under 500 m a day.
- Drink enough to stay hydrated, and no alcohol while you are travelling up or climbing.
- Trek with an experienced guide, and make sure your insurance names your maximum altitude and covers helicopter evacuation.
Broken sleep is normal up there. Many people jolt awake after a pause in their breathing, a pattern TravelHealthPro describes as alarming for everyone in the tent but usually harmless. It is not a reason to reach for sleeping tablets; if you normally use them, raise it at your consultation and we will look at whether they are sensible for this trip.
What does a sensible acclimatisation itinerary look like?
The same rules play out differently on each of the big trips, and this is where most of a consultation goes. Bring your operator's day-by-day schedule and we will read the sleeping heights off it with you.
- Kilimanjaro (5,895 m): TravelHealthPro classes an ascent in under seven days as very rapid and high risk. The cheap five-day itineraries are the ones people regret; a longer route with a genuine acclimatisation day is the best decision you will make before leaving Manchester.
- Everest Base Camp (just over 5,300 m): the classic trek gains height over more than a week and builds in acclimatisation days on the way up. Keep them. Groups that drop a rest day to catch a flight home are the ones who end up walking back down early.
- Inca Trail and Cusco (3,399 m): most people fly from Lima at sea level to Cusco in about an hour, which is the exact jump the guidance warns about. Two or three easy days in Cusco or the lower Sacred Valley before the trail starts make a real difference, and it is why operators insist on them.
- La Paz (3,630 m) and Lake Titicaca: the city is high and the airport on the plateau above it is higher still. Plan nothing strenuous for the first day or two and treat the whole first week as acclimatisation.
- Ladakh (Leh, around 3,500 m): the flight from Delhi is a one-hour climb to 3,500 m. A full rest day in Leh before any driving is the minimum, and the road passes above 5,000 m are not day-one territory.
- Aconcagua (6,960 m) and other expeditions: this is expedition medicine with its own medical plan. We can still cover prevention, medication where appropriate and your travel vaccines, but your expedition's medical lead must know about any condition you have.
- Alpine skiing (Val Thorens and the higher resorts): usually fine, but if you have reacted before, take the first afternoon easy, skip the après-ski on night one and drink water.
What does a pharmacy consultation cover, and what does the medication really do?
A pre-trip altitude consultation at our Timperley pharmacy is a conversation about your route, not a prescription pad. We go through your sleeping altitudes day by day, ask about previous trips, your health and current medicines, and agree what you will do if someone in the group becomes unwell. If you are a Trafford or Cheshire trekking group flying out of Manchester Airport, come in together so everyone hears the same plan.
What we go through
- Your itinerary against the ascent-rate guidance, and where a rest day would earn its keep.
- Any previous altitude illness, which tells us more than anything else.
- Existing conditions and regular medicines, with referral to your GP or a specialist where needed.
- Recognising AMS, HACE and HAPE, and the descent plan for your group.
- Insurance, evacuation cover and the first-aid kit worth carrying.
- Travel vaccines and antimalarial tablets for the same trip, so it is one visit.
What the medication can and cannot do
- It is a prescription medicine that speeds acclimatisation, considered on top of gradual ascent for moderate and high-risk itineraries.
- Low-risk trips do not need it; slow ascent does the job on its own.
- It is not a substitute for a sensible ascent rate, and it does not treat HACE or HAPE, which need descent.
- It is not suitable for everyone, including in pregnancy and with certain drug allergies; a short trial before travel is often suggested to check for side effects.
- Whether it is right for you, and how you would take it, is confirmed at your consultation.
Because it is a prescription-only medicine we cannot sell it over the counter or simply on request. It is supplied on prescription after the assessment, where it is appropriate for your route and your health.
Should children, pregnant women or people with health conditions get advice first?
Yes, and the advice differs for each. Children are not thought to be at higher risk than adults, and trips up to 2,500 m are considered low risk for healthy children, but younger ones, especially those too small to describe a headache or nausea, are hard to assess, so a family trek needs a lower ceiling and a slower pace. In pregnancy, TravelHealthPro advises avoiding high altitude in the first trimester; after 20 weeks, short stays up to 2,500 m without heavy exercise are thought to pose minimal risk, while sleeping above 3,000 m or travelling to remote areas is not advisable. Heart and lung conditions such as angina, COPD or some forms of congenital heart disease can worsen at altitude or raise the risk of altitude illness, and remote trailheads have little medical care. In all of these cases we talk it through with you and refer you to your GP or specialist rather than guess.
Which trips does this apply to?
Anything that takes you above about 2,500 m, whether you walk up or land there. The ones we see most often at our Altrincham clinic:
- East Africa: Kilimanjaro and Mount Kenya, alongside your travel vaccines for Tanzania.
- Himalaya: Everest Base Camp, the Annapurna Circuit, Ladakh and Lhasa, with vaccines for Nepal sorted at the same visit.
- Andes: the Inca Trail and Cusco (Peru travel vaccines), La Paz and Titicaca (Bolivia travel vaccines), Quito, and Aconcagua.
- Elsewhere: Mount Kinabalu (4,095 m), Mount Fuji (3,776 m), Toubkal in the Atlas, and the higher Alpine resorts.
Flying from Manchester Airport? Our travel clinic near Manchester Airport page explains how to fit a consultation in before a departure from Terminal 1, 2 or 3.
Altitude FAQ
Altitude sickness: your questions answered
Important: this page is general information drawn from NaTHNaC (TravelHealthPro) and NHS guidance and is not a substitute for a personal consultation. Altitude-sickness medication is a prescription-only medicine supplied only after an individual assessment, and it never replaces gradual ascent. Anyone with signs of HACE or HAPE needs immediate descent and urgent medical care. Sources: TravelHealthPro: altitude illness factsheet · NHS: altitude sickness. Contains public sector information licensed under the Open Government Licence v3.0.
Heading somewhere high?
Bring your itinerary to our Timperley pharmacy, two Metrolink stops from Altrincham, and we'll check the ascent rate, agree a descent plan, assess you for prescription altitude-sickness medication and sort the vaccines for the same trip. Walk in, or book a same-day appointment; we're open until 9pm most nights.