---
title: "Preventing altitude illness in adults: preparing travelers for >2500 m"
id: "bmj-0-prevention-of-altitude-illness-in-adults-preparing-people-for-travel-to-high"
canonical_url: "https://medichelpline.com/clinical-feed/bmj-0-prevention-of-altitude-illness-in-adults-preparing-people-for-travel-to-high"
content_type: "clinical_feed_article"
specialty: "General"
source_name: "BMJ"
source_url: "http://www.bmj.com/content/394/bmj-2026-100532.short?rss=1"
published_at: "2026-09-02T10:06:37.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Preventing altitude illness in adults: preparing travelers for >2500 m
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/bmj-0-prevention-of-altitude-illness-in-adults-preparing-people-for-travel-to-high
- **Specialty:** [General](https://medichelpline.com/clinical-feed/general.md)
- **Primary Source:** BMJ
- **Source URL:** [Original Journal Publication](http://www.bmj.com/content/394/bmj-2026-100532.short?rss=1)
- **Published At:** 2026-09-02T10:06:37.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- Altitude illness is an umbrella term for syndromes occurring in unacclimatised people who travel above **2500 m**, and ranges from **acute mountain sickness (AMS)** to life threatening **high altitude cerebral oedema (HACE)** and **high altitude pulmonary oedema (HAPE)**. - Symptoms typically appear during or after the first night at high altitude; mild lightheadedness or increased respiratory rate on immediate arrival may be normal. - The main preventable risk factor is the **rate of ascent**; safe ascent recommendations from guideline bodies emphasise limiting sleeping altitude gain and including **acclimatisation** days. - People with previous altitude illness, those who ascend rapidly (>500 m sleeping altitude gain per day), trekkers, support staff, miners, and military personnel are among higher risk groups. - Physical fitness and younger age are not protective against altitude illness; intense exertion increases risk regardless of baseline fitness. - Pre-travel assessment should cover comorbidities and stability, history of altitude illness, detailed travel plans (sleeping altitudes, itinerary, descent possibilities), expected exertion, local medical support, and insurance including medical evacuation. - Validated risk stratification tools and the 2024 Wilderness Medical Society (WMS) and UIAA guidance are recommended resources for clinicians advising travellers. - Management principles include stopping further ascent for mild–moderate AMS and immediate descent plus medical attention for severe AMS, HACE, or HAPE. - The source article provides guidance based on 2024 WMS and UIAA updates and the authors’ experience; the provided source text is truncated and further specific recommendations (pharmacological prevention details, specific ascent rates beyond general guidance, and full tables) were not reported in the provided excerpt.
## Clinical Analysis & Structured Key Points
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Prevention of altitude illness in adults: preparing people for travel to high altitude CCBY Open access Practice Practice Pointer # Prevention of altitude illness in adults: preparing people for travel to high altitude BMJ 2026; 394 doi: (Published 02 September 2026) Cite this as: BMJ 2026;394:e100532 * [Article](https://www.bmj.com/content/394/bmj-2026-100532 "Article Tab - Article")[](https://www.bmj.com/panels_ajax_tab/jnl_bmj_tab_art/node:1127076/1 "Article Tab - Article") * [Related content](https://www.bmj.com/content/394/bmj-2026-100532/related "Article Tab - Related Articles")[](https://www.bmj.com/panels_ajax_tab/jnl_bmj_tab_related_art/node:1127076/1 "Article Tab - Related Articles") * [Metrics](https://www.bmj.com/content/394/bmj-2026-100532/article-info "Article Tab - Info & Metrics")[](https://www.bmj.com/panels_ajax_tab/jnl_bmj_tab_info/node:1127076/1 "Article Tab - Info & Metrics") * [Responses](https://www.bmj.com/content/394/bmj-2026-100532/rapid-responses "BMJ Article Related Rapid Responses")[](https://www.bmj.com/panels_ajax_tab/bmj_related_rapid_responses/node:1127076/1 "BMJ Article Related Rapid Responses") * [Peer review](https://www.bmj.com/content/394/bmj-2026-100532/peer-review "Article Tab - Peer review")[](https://www.bmj.com/panels_ajax_tab/jnl_bmj_tab_peer_review/node:1127076/1 "Article Tab - Peer review") * [](https://www.bmj.com/content/394/bmj-2026-100532/submit-a-rapid-response "BMJ Rapid Responses Form")[](https://www.bmj.com/panels_ajax_tab/bmj_rapid_responses_form/node:1127076/1 "BMJ Rapid Responses Form") ![Loading](https://www.bmj.com/sites/all/modules/contrib/panels_ajax_tab/images/loading.gif) 1. Sudeep Adhikari, consultant physician, internal medicine[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#aff-1), 2. Rudy Zimmer, primary care physician[2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#aff-2), 3. Hermann Brugger, primary care mountain medicine physician[3](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#aff-3), 4. Nischal Bajracharya, patient representative[4](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#aff-4), 5. Buddha Basnyat, consultant physician, internal medicine[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#aff-1) 1. 1Oxford University Clinical Research Unit—Nepal, Lalitpur, Nepal 2. 2Richmond Square Medical Centre, Calgary, Canada 3. 3Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy 4. 4Patient author, Kathmandu, Nepal 1. Correspondence to S Adhikari sudeepadh123{at}gmail.com ### What you need to know * Support individuals to pursue safe and responsible high altitude travel by offering and signposting to sources of accurate and practical advice on prevention and recognition of altitude illness. * Understand that tools exist to stratify altitude illness risk, and that a high level of baseline physical fitness and younger age are not protective against altitude illness. * Risk can be managed by modification of travel plans and, in some cases, pharmacological prevention. Altitude illness is a collective term for syndromes that can occur in unacclimatised people who travel to destinations higher than 2500 metres above sea level.1,2,3 Altitude illness is potentially life threatening; however, it is preventable and manageable with adequate pre-travel planning and preparation. Here, we offer guidance on how to advise patients regarding travel to altitudes higher than 2500 m above sea level, and when to consider directing patients to a travel medicine expert with altitude illness experience. The recommendations are based on 2024 Wilderness Medical Society (WMS) guidelines,[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-1) the 2024 update of the 2012 Union Internationale des Associations d’Alpinisme (UIAA) Medical Commission guidelines,[2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-2)and the authors’ clinical experience. ## What is altitude illness and who might be affected? Inform anyone requesting advice regarding travel to high altitudes ([box 1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#boxed-text-2)) about the signs and symptoms of altitude illness and how to recognise them. Box 1 ### Frequently visited high altitude destinations[4](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-4)[26](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-26) * High altitude (2500-3500 m): Ski resorts in the Colorado Rockies, US and European Alps; high altitude cities with international airports such as Bogota, Quito, Cusco, La Paz (Andes mountains), and Lhasa (Tibetan plateau). * Very high altitude (3500-5500 m): Trekking to Everest base camp or completing the Annapurna circuit over Thorong La in Nepal, or travel across the Altiplano plateau in Andes, South America. * Extremely high altitude (>5500 m): Climbing Mount Kilimanjaro in Tanzania (the highest peak on the African continent at 5900 m) or Mount Aconcagua in Argentina (the highest peak in the Americas at 6961 m). [RETURN TO TEXT](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#xref-boxed-text-2-1) People with a history of altitude illness, or who ascend rapidly (more than 500 m per day, [box 2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#boxed-text-3)) to high altitude environments are at the greatest risk of developing altitude illness.[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-1)[3](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-3)This could include recreational trekkers, professional mountaineers, support teams (eg, porters carrying luggage), and those ascending for work, for example miners and military personnel.[4](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-4)[5](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-5)[6](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-6) Box 2 ### Definitions of commonly used mountain medicine terms[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-1)[2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-2) * Sleeping altitude: The altitude above sea level at which an individual sleeps or plans to sleep overnight. (WMS and UIAA guidelines consider sleeping altitude more relevant in determining risk of altitude illness than the maximum altitude reached during the daytime). * Sleeping altitude gain: The increase in sleeping altitude between two consecutive nights, expressed in metres. For example, if a traveller spends one night at an altitude of 3200 m and ascends over the day to an altitude of 4000 m to spend the subsequent night, then the sleeping altitude gain for that day is 800 m. * Rate of ascent: The sleeping altitude gains in metres between two consecutive nights during the ascent, when travelling above 3000 m above sea level. The suggested safe ascent rate in WMS and UIAA guidelines is 300-500 m per day. * Rapid ascent: A rate of ascent that is more than 500 m sleeping altitude gain between two consecutive nights of high altitude travel. This increases the risk of altitude illness. For example, if a traveller spends the night at an altitude of 3200 m and the subsequent night is spent at an altitude lower than 3700 metres above sea level, this would be a safe rate. Spending the subsequent night at an elevation above 3700 m would increase the risk of altitude illness. * Acclimatisation: The physiological adaptation to the lower atmospheric air pressure (and reduced availability of oxygen) at higher altitudes. One way of achieving acclimatisation at high altitude is sleeping one or more extra days at the same elevation above sea level, after every 1000 m gain of the sleeping altitude. Note: trekking operators will often build an extra day into the itinerary for every 2-3 days of gain to allow for acclimatisation, assuming a rate of ascent of 300-500 m per day. * Hypobaric hypoxia: Hypoxia (lower tissue oxygen supply) that occurs due to lower partial pressures of oxygen in the alveoli, resulting from decreased barometric pressures at high altitudes. The concentration of oxygen (about 21%) in air remains the same at sea level and high altitude, but the availability of oxygen for breathing drops at higher altitude owing to a drop in its partial pressure (as per Dalton’s Law). [RETURN TO TEXT](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#xref-boxed-text-3-1) The spectrum of altitude illness ranges from symptoms of acute mountain sickness (AMS) to life threatening high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) ([table 1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#T1)).[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-1)[3](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-3)[7](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-7)[8](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-8) Peripheral oedema can occur at high altitudes, but is not specific to altitude illness.[9](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-9)AMS, HACE, and HAPE are all associated with hypobaric hypoxia ([box 2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#boxed-text-3)).[10](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-10)[11](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-11)AMS and HACE involve cerebral pathophysiology resulting from increased cerebral blood volume and intracellular oedema in response to the hypoxia,[10](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-10) and HAPE is a form of non-cardiogenic pulmonary oedema due to exaggerated hypoxic pulmonary vasoconstriction and elevated pulmonary artery pressure.[11](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-11) AMS may occur in up to 25% of people with rapid ascent above 2500 m.[4](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-4) HACE may occur in up to 1% of travellers at 4000-5000 m, and HAPE in up to 6% at 4500 m.[12](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-12) Table 1 Clinical features and prognoses of altitude illnesses View this table: * [View popup](https://www.bmj.com/highwire/markup/1127077/expansion?width=1000&height=500&iframe=true&postprocessors=highwire_figures%2Chighwire_math) * [View inline](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1) When travelling to altitudes >2500 m, if symptoms suggestive of altitude illness ([table 1)](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#T1) develop, it should be considered altitude illness until proved otherwise and we advise patients to cease further ascent for mild or moderate AMS symptoms or to descend for severe AMS symptoms, HACE, or HAPE and seek medical attention. ### Symptoms on arrival at high altitude destinations Improved access and transportation have enabled travel to high altitude environments without acclimatisation. Symptoms of altitude illness typically appear during or after the first night at such locations, and not immediately on arrival; however, experiencing mild lightheadedness or tachypnoea (increased respiratory rate) on arrival are normal responses to initial exposure to hypobaric hypoxia. ## How are people assessed before high altitude travel? Ideally, individuals considering travel to high altitude regions would seek advice prior to booking the trip. To stratify health risk, including for altitude illness, clinicians may consider assessment of general fitness, capacity to undertake increased physical exertion, and capacity to tolerate hypoxia. It is important that clinicians advise their patients that physical fitness is not protective against altitude illness. Intense physical exertion (increased oxygen demand over baseline needs) increases risk of altitude illness, irrespective of physical fitness, and extra acclimatisation days help to decrease the exertion during the trip. ### Initial assessment WMS guidelines[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-1) and the UIAA Medical Commission[2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-2) recommend asking the following questions: * Does the person have comorbidities and are these medical conditions currently stable? * Do they have a history of known or suspected altitude illness? * Discuss travel plans, including: destinations, maximum sleeping altitudes, possibilities for descent by at least 500 m per day, medical evacuation plans, modes of travel, and planned activities. If available, ask for trekking itineraries, which can help assess altitude illness risk. * Discuss expected exertion during the trip. * Are extra acclimatisation days ([box 2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#boxed-text-3)) built into the itinerary? What local medical facilities will be available during travel, including medical personnel with the travel team, if any? * Has adequate travel medical insurance been purchased, including insurance that covers in-country treatment, as well as medical evacuation from higher altitude remote locations to lower altitude urban locations with adequate medical facilities? ### Stratifying risk of altitude illness Validated tools or resources such as given in 2024 WMS guidelines can be used to stratify risk of altitude illness.[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-1)[2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-2)[4](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-4)Consider the factors summarised below and in [table 2](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#T2) when stratifying risk of altitude illness: Table 2 Summary of the risk stratification scheme, as recommended by the WMS 2024 guidelines[1](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1#ref-1) View this table: * [View popup](https://www.bmj.com/highwire/markup/1127079/expansion?width=1000&height=500&iframe=true&postprocessors=highwire_figures%2Chighwire_math) * [View inline](https://www.bmj.com/content/394/bmj-2026-100532.short?rss=1) #### Rate of ascent This is the most important risk factor for developing altitude illness. The patient’s travel itinerary should provide the information required to inform this assessment. Consider the mode of transportation and time
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