Altitude Sickness: How to Stay Safe on High-Altitude Adventures

What Is Altitude Sickness?

Altitude sickness — also known as acute mountain sickness (AMS) — is a condition that can affect anyone who ascends to high altitude too quickly, typically above 2,500 metres (roughly 8,200 feet). It occurs because the air at high altitude contains less oxygen, and the body needs time to adapt to these lower oxygen levels. When ascent is too rapid, the body doesn't have enough time to acclimatise, and symptoms of altitude sickness can develop. In its milder form, altitude sickness causes headaches, nausea, fatigue, dizziness, and difficulty sleeping. In severe cases, however, it can progress to life-threatening conditions including High Altitude Pulmonary Oedema (HAPE) — fluid in the lungs — and High Altitude Cerebral Oedema (HACE) — fluid on the brain.

At Travel Clinic Bedford, operated by Goldharts Pharmacy, we provide expert altitude sickness advice in Bedford for trekkers, climbers, and adventurous travellers heading to high-altitude destinations around the world. From the Himalayas and Kilimanjaro to the Andes and the Tibetan Plateau, altitude sickness is a genuine risk — but with the right preparation, it is manageable and largely preventable.

Who Is at Risk of Altitude Sickness?

One of the most important things to understand about altitude sickness is that it can affect absolutely anyone, regardless of age, fitness level, or previous experience at altitude. Young, fit athletes are just as susceptible as older, less active travellers. Interestingly, previous successful acclimatisation at altitude does not guarantee that you won't experience altitude sickness on your next trip — your susceptibility can change between visits. There is no reliable way to predict in advance who will and who won't be affected.

That said, certain factors may increase your risk. Ascending too quickly is the most significant risk factor — the faster you climb, the less time your body has to adapt. A history of altitude sickness on previous trips is also a strong predictor of future susceptibility. Living at low altitude, as most UK residents do, means your body is not routinely adapted to reduced oxygen levels, which is why altitude sickness is so commonly encountered among travellers visiting high-altitude destinations for the first time.

Popular Destinations Where Altitude Sickness Is a Risk

Many of the world's most popular adventure travel destinations involve significant altitude. Some of the most frequently visited high-altitude destinations include:

Nepal and the Himalayas — Trekking to Everest Base Camp (5,364 metres), the Annapurna Circuit, and other classic Himalayan trails involves several days at altitudes well above 3,500 metres. Altitude sickness is a common reason for trekkers having to cut their trips short, and in severe cases it can be fatal.

Kilimanjaro, Tanzania — Africa's highest peak at 5,895 metres is popular with trekkers seeking a non-technical summit. The relatively fast ascent profiles of popular routes mean altitude sickness rates are high, with some studies suggesting over three-quarters of trekkers experience some degree of AMS.

The Andes, South America — Destinations such as Machu Picchu in Peru (2,430 metres), Cuzco (3,399 metres), and La Paz in Bolivia (3,640 metres) involve significant altitude. Many travellers fly directly to high-altitude cities, giving the body very little time to acclimatise.

Tibet and Yunnan, China — Lhasa, the Tibetan capital, sits at 3,656 metres, and many destinations across the Tibetan Plateau exceed 4,000 metres. The altitude encountered when visiting this region is significant and should not be underestimated.

The Alps and European mountains — While generally lower than the Himalayas or Andes, skiers, mountaineers, and trekkers can still encounter altitudes above 3,000–4,000 metres in the Alps, where AMS is possible.

Symptoms of Altitude Sickness

Acute Mountain Sickness typically develops within six to twelve hours of reaching altitude. The key symptoms include headache — the hallmark symptom — fatigue, loss of appetite, nausea or vomiting, dizziness, and poor or interrupted sleep. In mild cases, these symptoms often resolve within one to two days if you stop ascending and rest at the same altitude. However, if symptoms worsen or new symptoms develop, this may indicate progression to more serious forms of altitude illness.

High Altitude Pulmonary Oedema (HAPE) is characterised by extreme breathlessness at rest, a cough that may produce frothy or pink-tinged sputum, a feeling of tightness in the chest, and cyanosis. HAPE is a medical emergency and the most common cause of death from altitude illness. It can develop very rapidly, and immediate descent and supplemental oxygen are essential.

High Altitude Cerebral Oedema (HACE) is the most severe form of altitude sickness and involves swelling of the brain. Symptoms include severe, persistent headache unresponsive to simple pain relief, loss of coordination, confusion, altered consciousness, and eventually coma. HACE can be fatal within hours if not treated. As with HAPE, immediate descent is the most important intervention.

Prevention: The Golden Rules of Altitude Acclimatisation

The most effective way to prevent altitude sickness is to ascend gradually and give your body the time it needs to adapt. The widely accepted guideline is not to increase your sleeping altitude by more than 300–500 metres per day once above 3,000 metres, and to include a rest day approximately every three days. Planning your itinerary carefully with proper acclimatisation built in is one of the most important things you can do to protect yourself.

Other important preventive measures include staying well hydrated — dehydration worsens altitude sickness symptoms — avoiding alcohol and sleeping tablets in the early days at altitude, eating a balanced diet even if appetite is reduced, and avoiding strenuous exertion in the first few days after arriving at high altitude. Physical fitness does not protect against AMS, but maintaining good overall health before travel is beneficial.

Medication for Altitude Sickness Prevention

For travellers at higher risk of altitude sickness, or those following itineraries where gradual acclimatisation is not possible — for example, those flying directly to high-altitude cities — medication may be appropriate. The most commonly used medication for altitude sickness prevention and treatment is acetazolamide (Diamox).

Acetazolamide works by stimulating faster and deeper breathing, which increases the oxygen content of the blood and helps the body acclimatise more quickly. It is typically started one to two days before ascent and continued for two to three days at high altitude. Side effects include increased urination, tingling in the hands and feet, and a change in the taste of carbonated drinks. It is contraindicated in those with sulphonamide allergy and should be used with caution in certain other conditions.

At Travel Clinic Bedford, our travel health advisors can assess whether acetazolamide is appropriate for you, discuss the correct dosage and regimen, and advise you on what to do if you develop symptoms despite taking medication. We will also discuss other medications — such as dexamethasone for HACE and nifedipine for HAPE — that may be considered as emergency treatments for severe altitude illness.

What to Do If You Develop Altitude Sickness

If you develop symptoms of altitude sickness, the most important rules are: do not ascend further, and if symptoms are moderate to severe, descend immediately. Even descending by just a few hundred metres can produce a significant improvement in symptoms. Never ignore symptoms or continue climbing in the hope that they will resolve on their own — altitude sickness can progress rapidly and become life-threatening.

For mild symptoms, rest at the same altitude, stay well hydrated, take simple pain relief for headaches, and wait for symptoms to improve before ascending further. Supplemental oxygen, if available, can also help. For moderate or severe symptoms — particularly those suggesting HAPE or HACE — descend immediately, administer supplemental oxygen if available, and seek emergency medical care.

Your Altitude Sickness Consultation at Travel Clinic Bedford

Before embarking on any high-altitude adventure, it is strongly advisable to speak with a qualified travel health professional. At Travel Clinic Bedford, our team can review your itinerary and planned ascent profile, assess your personal risk factors, advise on whether medication is appropriate, provide a prescription for acetazolamide if indicated, and equip you with a comprehensive understanding of altitude sickness symptoms, prevention, and emergency management. We also provide advice on the full range of travel health services — including travel vaccinations and malaria prevention advice for destinations where both altitude and malaria may be relevant concerns.

As part of Goldharts Pharmacy, we provide professional, personalised travel health advice in a welcoming, accessible environment. We believe that thorough preparation is the key to a safe and enjoyable adventure — and that preparation begins with speaking to the right people before you go.

Book Your Altitude Sickness Consultation in Bedford Today

Planning a trek to Everest Base Camp, Kilimanjaro, the Andes, or any other high-altitude destination? Don't leave it to chance. An altitude sickness consultation at Travel Clinic Bedford will give you the knowledge, the tools, and where appropriate the medication to help you stay safe at altitude and make the most of your adventure.

We recommend booking your appointment at least four to six weeks before departure wherever possible. Book your altitude sickness consultation now and take your first step towards a safe and successful high-altitude journey.