top of page

The Pro's and Con's of Diamox for Altitude Sickness - by Dr Nicki Russel

Updated: Sep 27, 2018

Dr Nicki Russel, PJS Challenges Medical Expert

Acetazolamide, otherwise known as Diamox, is a drug often used by people who trek to altitude for prevention of acute mountain sickness. There has been some debate about whether Diamox should be used and there is still uncertainty about its effectiveness. However, I have tried to summarise some of the research that’s available for you to consider if you’re thinking about using it.

Key words

Acclimatisation: This is the body’s way of coping with the change in oxygen levels at altitude.

Acute mountain sickness (AMS): This is when the body is unable to cope with the low oxygen levels. Signs and symptoms include headaches, dizziness, nausea and vomiting, shortness of breath, fatigue and sleep disturbance. If allowed to worsen, AMS can be life threatening.

What happens to oxygen levels at altitude?

The level of oxygen is significantly less at altitude. The body tries to respond to this in several ways. Firstly, the breathing rate will increase to try to take more oxygen into the body. The heart rate will also increase to pump as much oxygen as possible around the body.

Why does AMS happen?

AMS happens because the body cannot respond to the low oxygen levels. The exact reason why this happens to some people and not others is unclear. There is no way to predict who will suffer from AMS but those who have had it before are at greater risks of having it again.

How does Diamox work?

Diamox works on the kidneys to make the blood more acidic. Increasing acid levels in the blood will make the person breathe more rapidly, thereby increasing oxygen levels. However, this effect on the kidneys also increases the amount of urine that is produced.

The kidneys may become damaged if you don’t drink enough to replace the fluid lost in this way. Kidney injury is unusual but dehydration can become a significant problem, particularly when exerting yourself at altitude. If you have long-standing kidney problems, you must consult a Doctor before taking Diamox.

Evidence for the use of Diamox

There is an abundance of literature available about Diamox and its effectiveness. Analyses of multiple research papers have shown that Diamox is consistently more effective than not taking any medications for prevention of acute mountain sickness.

There is evidence to suggest that Diamox is effective at its lowest dose of 250mg per day (125mg twice daily). The risk of side effects at this dose are lower than at higher doses. It has been shown to be useful in preventing altitude sickness, particularly when high altitude climbing begins prior to acclimatisation.

As with most medications, there are several side effects of Diamox. These are experienced more with higher doses but are still common at the lowest dose. They include altered taste, nausea and vomiting, tingling in the fingers and toes and frequent urination.

There are also possible interactions with other medications such as high dose Aspirin (300mg) and Metformin. Diabetics and those with heart disease should seek specific advice before taking Diamox.

Should I take Diamox?

Recommendations have been made by the Wilderness Medicine Society about who should take Diamox, given the evidence for its effectiveness. The table below guides who should take prophylaxis, based on the risk-benefit argument: reducing risk of AMS v side effects of Diamox.


· People with no history of altitude illness who are ascending to less than 2800 m

· Those taking 2 days to arrive at 2500-3000 m with subsequent increases in sleeping height of <500 m/day and an extra day for acclimatisation every 1000m

Suggested approach: prophylactic drugs are not usually necessary.


· People with a history of altitude illness who are ascending to 2500-2800m in one day

· Those with no history of acute mountain sickness but who are ascending above 2800m in one day

· All people ascending 500 m/day (increase in sleeping height)at altitudes 3000m but with an extra day for acclimatisation every 1000 m

Suggested approach:consider acetazolamide(Diamox)125 mg twice daily.


· People with a history of acute mountain sickness who are ascending to above 2800m in one day

· Those with a history of high altitude cerebral oedema

· Climbers ascending to 3500m in one day and those ascending 500m/day (increase in sleeping height) above 3000m without extra days for acclimatisation

· Very rapid ascents (eg, ascent of Mt Kilimanjaro in less than 7 days)

Suggested approach: strongly consider acetazolamide(Diamox)125 mg twice daily.


I have supported the use of Diamox by travellers, particularly when there is little time for acclimatisation. If used correctly, the chance of successful and safe summit can be increased. However, the key things to remember are:

· Diamox will make you urinate more than you would normally. Therefore, you need to take responsibility of also drinking more than you might at home. You will be doing challenging exertional work and losing fluid from sweat, urine and breathing. If you don’t drink to compensate for this, you may become very unwell.

· You must ensure you aren’t taking any medications that may interact with Diamox

· It is important to contact your Doctor if you have diabetes, kidney or heart problems prior to starting Diamox

· Diamox is used to help you acclimatise but is not a substitute for preparing your body in other ways. Do not rely on it alone. Make sure you are fit to travel by maintaining a good level of fitness and if possible, try to spend time at altitude prior to any trekking.

· Diamox can be used by medical professionals or challenge leaders at a higher dose to help you cope at altitude if you do have symptoms of altitude sickness. However, this is not the best treatment. If you become ill at altitude, you must follow the advice of your challenge leaders about whether to continue your climb. The safest and best treatment is to DESCEND to where oxygen levels in your blood will be higher.

If you have any concerns prior to travel, please contact your Doctor or PJS Challenges for advice

473 views0 comments


bottom of page