Where My Perspective Comes From

I’ve been working in the mountains for over thirty years, guiding at altitude across the Himalaya and beyond.

When I was new to it, I made the same mistake I now see in others.

I was young, fit, and convinced that I was strong enough to deal with anything altitude could throw at me.  I pushed too quickly, ignored the signals (probably because I didn’t really know what they were), and paid for it.  I suffered from altitude sickness because I behaved as if I was immune.

That experience shapes how I look at this now.

I’ve used Diamox.  I understand where it fits and how it can help.  But I’ve also learned, through experience rather than theory, that the real discipline at altitude is not what you take, it is how you move.

These days, I rely on natural acclimatisation.  Gradual ascent, well placed rest days, hydration, nutrition, and honest self-assessment.  Diamox sits in my medical kit as a reserve, not as a default.

How the Diamox Narrative Takes Hold

Most people heading to altitude are doing it for the first time.

They are stepping into an unfamiliar environment and trying to make sense of the risks.  That is entirely reasonable.

The problem is where they look for guidance.

Much of the advice online comes from people with very limited experience.  First time trekkers or those who have completed a single trip.  They took Diamox, they had no issues, and they draw a simple conclusion.

Diamox worked.

What they cannot know is whether they would have acclimatised perfectly well without it.  Whether their itinerary was already well planned to give them the best chance.  Whether good pacing, hydration, and rest days did the real work.

The outcome was positive, so the drug gets the credit.

Repeat that often enough and it becomes the accepted truth.

This is how the idea of using Diamox for altitude sickness becomes normalised, often without being properly questioned.

Nuance gets lost.  Experience gets drowned out.  Simple messages win.

What Diamox Actually Does

Diamox, or acetazolamide, has a legitimate role in altitude medicine.

It supports acclimatisation by stimulating breathing and improving oxygenation, particularly during sleep.  Used appropriately, it can reduce the likelihood of Acute Mountain Sickness.

But it is not a guarantee.

It does not make you immune to altitude sickness.  It does not compensate for a poor itinerary or rapid ascent.  If you climb too quickly or ignore early symptoms, you can still develop AMS, and more serious conditions such as HACE and HAPE.

Guidance from the Wilderness Medical Society makes it clear that acclimatisation is the primary defence, with Diamox used selectively rather than routinely.

If you are new to altitude, it is worth understanding the fundamentals properly before thinking about medication.  A good place to start is understanding the basics of Acute Mountain Sickness and how it develops, as well as recognising the warning signs of more serious conditions like HACE and HAPE.

NHS guidance on altitude sickness highlights that symptoms are driven by how quickly you ascend, reinforcing the importance of proper acclimatisation.

The Foundations That Actually Keep You Safe

The fundamentals of acclimatisation are simple, but they require discipline.

Gradual ascent.  Well-structured itineraries.  Rest days in the right places.  Hydration that matches the demands of altitude.  Nutrition that supports recovery and adaptation.

These are not glamorous concepts, but they are the foundation of every successful high-altitude trip I have led.

If you want to go deeper into these areas, it is worth understanding how hydration at altitude affects performance and why food matters on high altitude treks far more than most people realise.

These are the things that keep people safe.

Not a tablet.

The Risk of Outsourcing Responsibility

There is a more subtle issue with the way Diamox is now discussed.

When it becomes the default answer, responsibility shifts.

It moves from understanding how to manage yourself at altitude to relying on something external to solve the problem.  That is an attractive idea, particularly for first time trekkers.

But it is also where risk begins to creep in.

Altitude does not negotiate.  It does not care how fit you are or what you have taken.  If anything, a sense of protection can change behaviour.  People move faster, push higher, and ignore early symptoms because they believe the risk has been dealt with.

This is something I explore more in the idea of Altitude, Pride and Ego, and how mindset influences decision making in the mountains.

The Kathmandu Problem

There is also a practical reality that adds to the issue.

In the UK, Diamox requires a prescription.  That is because it is a physiologically active drug with contraindications, side effects, and individual variability.  A GP or travel clinic should assess whether it is appropriate.

In Kathmandu, it is widely available over the counter.

No screening.  No structured advice.  Just easy access at the point where people are often tired, excited, and slightly overwhelmed.

Combine that with strong online messaging that says you should take Diamox for altitude sickness, and it is no surprise that many people do.

What you end up with is a system where low experience, high confidence, and easy access to medication combine.  It normalises behaviour that would not pass scrutiny at home.

A More Balanced View

This is not an argument against using Diamox for altitude sickness.

Diamox has a place.  I carry it in my first aid kit when working at altitude.

But it sits within a broader strategy.  It does not replace that strategy.

If you want a deeper view on this, I’ve written separately about why I believe in natural acclimatisation over Diamox, based on both personal experience and years of guiding.

Used well, Diamox for altitude sickness can support acclimatisation in the right circumstances.

Used blindly, it becomes a crutch.

Final Thought

If there is one thing worth challenging, it is this:

“The loudest voice does not always give the best advice.”

Especially in the mountains.

About the Author

Sam Marshall is the founder of Monkey Mountaineering and a UK-based mountaineering instructor with over 35 years’ experience climbing and leading expeditions in high-altitude and remote environments worldwide.

He has climbed on every continent and made 17 first ascents in a seldom-visited, remote region of northeast Greenland. His expedition experience includes the Army Everest West Ridge expedition and numerous Himalayan climbs, including the Southeast Ridge of Makalu, as well as Mera Peak, Lobuche East, Island Peak, Kusum Kanguru, Tharpu Chuli, Singu Chuli and Hiunchuli.

With a background in risk, disaster and crisis management, Sam’s approach is grounded in real-world experience rather than theory. He specialises in small teams, conservative decision-making, and well-structured acclimatisation strategies, helping people operate safely and effectively in complex mountain environments.