15/10/2026
High-altitude trekking can be dangerous without proper acclimatization. A new medical review highlights how gradual ascent, early symptom recognition, and careful preparation can help travelers reduce the risk of altitude illness.
As trekking and mountaineering take travelers into some of the world's highest landscapes, a new review published in The BMJ emphasizes a crucial message: altitude illness can affect even young, physically fit people, but careful planning can significantly reduce the risk.
Published on September 2, 2026, the review, Prevention of Altitude Illness in Adults: Preparing People for Travel to High Altitude, provides guidance for people planning trips above 2,500 meters (8,202 feet), including trekkers heading to Everest Base Camp, the Annapurna Circuit, and other high-altitude destinations.
The review was written by Sudeep Adhikari, Rudy Zimmer, Hermann Brugger, Nischal Bajracharya, and Buddha Basnyat. It draws on established mountain medicine guidelines and clinical experience.
➤ Gradual Ascent Is Essential
The review identifies the rate of ascent as the most important factor travelers can modify to reduce their risk of altitude illness.
Above 3,000 meters, a commonly recommended approach is to increase sleeping altitude by approximately 300–500 meters per day and include an additional acclimatization day for every 1,000 meters gained. Rapid ascent, especially sleeping at high elevations soon after arrival, increases the risk.
Altitude illness includes acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). While AMS is generally less severe, HACE and HAPE are potentially fatal emergencies.
Importantly, being young or physically fit does not protect someone from altitude illness. Previous experience at altitude, the planned itinerary, sleeping elevations, and the rate of ascent all matter.
➤ Recognizing the Warning Signs
Symptoms of acute mountain sickness may include headache, nausea, dizziness, fatigue, loss of appetite, and disturbed sleep. Symptoms often develop after the first night at altitude.
More serious warning signs include confusion, difficulty walking straight, or changes in mental status, which may indicate HACE. Unusual breathlessness during mild activity, a significant decline in exercise capacity, and a persistent cough can signal HAPE.
The review advises travelers to stop ascending if mild or moderate symptoms develop. Severe symptoms or suspected HACE or HAPE require urgent descent and medical assistance.
➤ Medication May Help, but Preparation Comes First
For people at moderate or high risk, preventive medication such as acetazolamide may be appropriate after consultation with a qualified healthcare professional. Other medications have specific roles in selected circumstances, including for people with a history of HAPE.
However, medication is not a substitute for gradual ascent, acclimatization, or a plan for emergency descent.
The authors also emphasize the importance of reviewing any history of altitude-related illness, planning extra acclimatization days, checking available medical support, and arranging appropriate travel insurance that covers evacuation from remote mountain areas.
For anyone preparing to trek or climb in the Himalayas, the central lesson is straightforward: plan the ascent carefully, recognize symptoms early, and never continue climbing when altitude illness is suspected.
----------
Source: Adhikari et al. “Prevention of altitude illness in adults: preparing people for travel to high altitude.” The BMJ, 2026.
