Breathlessness is normal. These symptoms are not
Above 3,000 metres, feeling short of breath on a climb is expected. A persistent headache that does not respond to water and rest, nausea, loss of appetite, disturbed sleep, or a feeling of mental fog are early signs of Acute Mountain Sickness (AMS), and worth telling your guide about immediately, even if they feel minor.
The warning signs that mean stop ascending entirely: confusion, loss of coordination, a cough producing pink or frothy fluid, or severe breathlessness at rest. These can indicate High Altitude Pulmonary or Cerebral Oedema, both medical emergencies that require immediate descent, not medication and a wait-and-see approach.
Why our itineraries build in extra days
The most reliable prevention is a slow ascent rate, roughly 300 to 500 metres of net sleeping-altitude gain per day above 3,000 metres, with a rest day roughly every 900 to 1,000 metres. This is why the Everest Base Camp itinerary has dedicated acclimatisation days at Namche and Dingboche rather than a straight climb. Shortening these days is the single most common cause of AMS we see in trekkers who have joined us after a cancelled trip elsewhere.
"Climb high, sleep low" is the practical version of this: a day hike to a higher point followed by a return to sleep lower helps the body adapt faster than staying flat at one altitude.
What we actually do about it
Every guide carries a pulse oximeter and checks oxygen saturation and pulse daily above 3,000 metres, logging it against how each trekker reports feeling. A guide has the authority to hold a trekker at altitude for an extra acclimatisation day, or send them down with a support crew member, regardless of the group's schedule. This is written into our operating procedure, not left to judgement calls under pressure.
Diamox (acetazolamide) can help some trekkers acclimatise, taken as a preventive starting a day before ascending, but it is not a substitute for a sensible ascent rate and it will not mask serious symptoms safely. Talk to a travel medicine doctor before your trip if you are considering it, not your trekking guide on day four.