Altitude sickness: what actually works, from a mountain doctor
Diamox, hydration myths, the symptoms that mean descend now, and why your acclimatisation schedule matters more than any drug.
Dr. Sunita Rai18 May 20266 min read
Acute mountain sickness affects a majority of trekkers above 4,000 metres to some degree, and almost none of them seriously. Knowing which category you are in is the entire skill.
Mild AMS is a headache, poor sleep, reduced appetite and mild nausea. It is common, it is not dangerous, and it usually resolves with a rest day at the same altitude. Do not gain elevation while symptomatic — that single rule prevents most serious cases.
The symptoms that mean descend, immediately and without discussion, are ataxia (unable to walk heel to toe in a straight line), confusion or altered behaviour, breathlessness at rest, and a persistent wet cough. These indicate HACE or HAPE. Both are treatable and both kill people who wait until morning.
Acetazolamide, or Diamox, genuinely works as a prophylactic — 125 mg twice daily starting the day before ascent. It is not a licence to climb faster. It also makes fizzy drinks taste strange and makes you urinate more, which is worth knowing before you attribute either to something else.
The hydration advice you will hear on the trail is overstated. Drink to thirst plus a little, roughly three to four litres a day. Force-drinking beyond that dilutes your sodium and creates a different problem, which at altitude looks confusingly like the first one.
None of this substitutes for the schedule. An itinerary that gains under 500 metres of sleeping altitude per day above 3,000 metres, with a rest day every 1,000 metres, will do more for you than any medication. Choose the trek with the extra acclimatisation day.
