How Diamox Deals With Acute Mountain Sickness (AMS)

Sometimes an unnecessary debate is on between purists and non-purists about acclimatization on a high altitude trek.

The purists feel that using drugs like Diamox to accelerate acclimatization goes against the spirit of trekking. They feel it is better to acclimatize naturally and ascend slowly with breaks – giving the body sufficient time to get used to the higher altitude.

On the other hand the non purists think it is better to be safe than suffer from high altitude sickness. They feel being on a course of Acetazolamide (Diamox) would give them maximum chance of success on a high altitude trek. So they start on a course of Diamox even before they begin their trek.


Now what is the right thing to do? Before I answer this question, a quick background on Acute Mountain Sickness (AMS) would help.

As one climbs above 8,000 feet, the atmospheric pressure starts to fall noticeably. As a result with every breath you take less oxygen reaches your blood. You must work harder to get the oxygen. Your body copes by breathing harder and longer. When you are climbing uphill, this is more acute. Persistent increased breathing builds up carbon dioxide in the blood.

The good news is as you climb higher your body acclimatizes naturally to the decreasing oxygen. Your body builds up a ‘zone of tolerance’ – where it can function normally even with the decreased oxygen. This zone of tolerance moves up as your body acclimatizes to the higher altitudes. However, when the build up of carbon dioxide is beyond your zone of tolerance your body reacts and you fall sick. This is AMS. You get high altitude sickness.

AMS is when along with headache you display the following symptoms:

I find it strange when at 11,000 feet trekkers complain of headache, and others around him say this is normal. It is not. A headache at an altitude is not normal. When you get a headache, drink one liter of water, pop a Disprin and watch for an hour (dehydration is a very common cause of headache). If your headache hasn’t totally disappeared within an hour then you are suffering from AMS. Do not stay at this altitude and begin your descent to the altitude where you last felt comfortable.

This brings me around to the use of Acetazolamide (Diamox) to assist acclimatization and prevent high altitude sickness.

The question is really not whether to use Diamox or not. The deciding factor to guide a trekker should always be the duration and the altitude gain of the trek. If you are doing a 6 day trek and going to high altitude (above 14,000 feet) then your body does not have enough time to acclimatize – even though you may have factored in a rest/acclimatization day. It is best to start on a course of Diamox before you start the trek. If on the other hand you are on a 12-14 days trek, then you have sufficient time to allow your body to acclimatize to the altitude. You don’t need Diamox to help acclimatization.

Generally, you need to allow your body to acclimatize 24-48 hours at an altitude (above 10,000 feet) before going higher. Modern day trekking, unfortunately, does not allow us this time. We usually arrive at a camp at around 2 pm and then have to move to the next higher camp early next morning, giving us less than 16-18 hours to acclimatize. This is usually not enough. Trekkers are prone to AMS under such conditions.

Follow this guide on your trek: if your trek schedule is short and does not allow you more than 24 hours at an altitude, then you are better off being on a course of Diamox.

I often get calls from trekkers telling me that they have been on several high altitude treks and that they have never had to use Diamox. I find this logic baffling. Anyone can get AMS. There is no significant effect of age, gender, physical fitness, or previous altitude experience on AMS. You may get AMS on any trek and it would be terrible if you have to give up on a trek because you did not take this elementary precaution.

What does Acetazolamide (Diamox) do?

90% of the blood’s carbon dioxide exists in a chemical called bicarbonate. This carbon dioxide after travelling through your blood is exhaled by your lungs. Diamox forces the kidneys to excrete bicarbonate from your body (when you urinate).

Your body doesn’t like that. It needs the bicarbonate to exhale carbon dioxide through your lungs.

When Diamox forces you to excrete biocarbonates, your blood, which is used to a certain level of acidity, becomes more acidic. When the blood gets acidic it believes that it has more carbon dioxide in it. So the body gets rid of this excess carbon dioxide in a simple way. It starts to breathe deeper and faster, getting rid of the carbon dioxide, and also taking in more oxygen.

In effect, the increased oxygen speeds up the acclimatisation process. It also greatly reduces you of any symptoms of altitude sickness. Which is why Diamox works best when you start on it a day or two before you get to high altitudes. 

In a recent conversation with Dr Venkatesh Thuppil, the leading expert in India on high altitude hypoxia and the co-inventor of the HAPO bag, he told me that the best step that a trekker could take to prevent any high altitude sickness was to be on a course of Diamox prior to the start of the trek. He said more lives could be saved and more treks successful if the trekkers were on a course of Diamox than without.

Remember, Diamox accelerates acclimatization. It does not cure anything. If you have headache with any of the above symptoms, even after taking Diamox, it means your acclimatization is not complete and you must descend. Under no circumstances should you climb higher if your symptoms still persists.

Diamox dosage

Start on a dosage of 125 mg every 12 hours 2 days prior to your trek (or when you arrive at Delhi). Increase it to 250 mg every 12 hours from the day you get to the base camp and continue until you complete the trek.

Side effects of Diamox

While Diamox is harmless for most people, please check with your doctor whether you are allergic to sulphides. Also check with your doctor if you have high/low blood pressure or diabetes.

Diamox is a sulfa-based drug. So if you’re allergic to sulphides, avoid Diamox.

At Indiahikes, earlier, we used Diamox only in emergencies – however, now we have reviewed our stand and we suggest participants start on Diamox two days before they start the trek. The chances of a successful and stress free trek is much higher if participants start on a course of Diamox on arrival at Delhi.

Altitude training

While Diamox reduces your chances of getting any high altitude sickness, it is important to prepare your lungs to be ready to work with less oxygen. The best way to do that is to prepare for a trek. A good altitude training program must include cardio-vascular, strength and flexibility training. I would recommend a run of half an hour and covering a distance of 4.5 km as good preparatory altitude training.

Meanwhile, it is important to acquaint yourself with AMS before setting off on a high altitude trek. This AMS manual authored by Sandhya will help.

A quick round-up of Acute Mountain Sickness

Click on the image to see the AMS Manual authored by Sandhya

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52 thoughts on “How Diamox Deals With Acute Mountain Sickness (AMS)

  1. We are a group of 12 family members ages starting from 5 years to 60 years who are going to Valley of Flowers and Hemkund Sahib around 13th August. Just read your articles on AMS and wanted to know how AMS might affect kids. We have 4 kids in the group on the trek. The youngest being 6 years old and the oldest is 10 years. Do we need to start them on Diamox 2 days before ? Or is there some other medication for kids?

  2. We are travelling to Leh as such below
    srinagar- kargil
    we have children with us from age 2 till 12, and elder people also. should we talk Diamox or this is a good trip for acclimatization with the weather.

  3. Hi. Im doing the Annapurna base camp trek later this year. It’s my first trek. Would you suggest then that I take the medication 2 days prior. It’s a 7 day trek. Thank you great article.

    1. Hi Sweeat, yes I would suggest that you begin with the prescribed dosage of diamox 2 days prior to when you start your trek. So it must be 2 days before you reach base camp.

  4. Hi,
    I am traveling to Leh, direct by flight from Delhi. When should i start or do i need to take diamox? pls advise.

      1. Hey hi Aswati
        We r family of 4 with two kids age 8 and 13. We r flying to leh from Delhi during May 3rd week.
        Do we need to start with Diamox before a start to leh.
        Kindly advice us

        1. Hi Gomathi,
          Yes, you can start off with half a tablet, twice a day two days before reach Leh. On the day you reach Leh ad preferably the next day as well, take it easy and do not do anything strenuous.

          1. Hi Gomathi,
            Yes, kids can also go on a preventive course from Delhi.
            On Day 1, you should just rest in the hotel. You can walk around Leh Market at the most.

  5. I am travelling to amarnath on 20th July. I am 62 yrs old and suffering from no and diabetes. Should I take the medicine before we climb.

  6. I’m Planning to cycle solo from Srinagar to Leh, I live in Srinagar (doubt if 5200ft helps with acclimatization?). Which would be better acclimatization wise?
    1) Srinagar – Sonmarg – Drass
    2) Srinagar – Gagangir – Baltal – Drass/Kargil (Drass/Kargil since it completely downhill from Zoji La, so depending upon my stamina I’ll decide where to stop)

    The highest point in the section would be Zoji La at about 11,600ft.

    The next passes Namki La(12,500ft) and Fotu La(13,500)ft will come after 5-7 days of beginning the journey. If there’s a better way to do the Srinagar-Drass Section other than the two options mentioned, please let me know. (I’ve always been a purist, and the ascent seems slow, but since this is a solo trip I’m breaking my head about whether to take Diamox or not!) Please advice!

    Thanks in advance!

    1. Hi Joel, you have quite a plan there! I can see that you are ascending more than 1000 ft a day. Watch this video to gain more clarity on where I am coming from. I would suggest you be on a preventive course of diamox to avoid AMS.

  7. Hi, So i have a large consumption of water on a daily basis (in excess of 5L). In my last trek which was the Bramhatal Trek I always had to be judicious with my water consumption even though I carried 2L with me. As per advice of the Trek staff I started with Diamox as well. Now knowing that Diamox is a diuretic it increases the tendency to urinate, but there isn’t enough water to meet the basic requirements of someone whose minimum uptake is a lot. I fail to understand the logic as to how would it have helped me.
    Kindly address my doubt as I am going for the Roopkund Trek soon.

    1. Hi Raghavendra
      The idea is to load yourself with water before and after the trek. This makes sense because we might not always find water on the trail. Since the trek only lasts for about 5 – 6 hours, its a good idea to take small sips of water during this time and compensate for it after you finish the trek and have reached your campsite. Hope this answers your query 🙂

    1. Hello Poorna
      The altitude of Vaishnodevi is too low to be considered for a dose of diamox. Neither your father nor you have to take diamox for visiting a place only 5,200 ft above sea level.

  8. Hi, Me and my wife (both in early 30s) are going to Leh via flight from Bangalore. Below is our approx day wise itenary.
    Day1: Rest
    Day2: Alchi & Likir Monastery, other places enroute.
    Day3: Nubra Valley, Overnight stay
    Day4: Return to Leh, overnight stay in Leh
    Day5: Pangong Lake, overnight stay in Pangong
    Day6: Tso kar, overnight stay in Tso Kar,
    Day7: Leh, overnight stay in Leh.

    We are planning to rent a bike and visit all these places. Do you suggest us to take Diamox?

  9. Hi, we are a group of 11 people and we are going for Spiti valley trip and our route is
    Delhi-Shimla-Rampur-chitkul-Kinnaur-Tabo-kaza-koumik-kibber-chandartaal -Keylong- manali-delhi
    Its an eight day trip.

    Please guide about when and how much mg of diamox we should take. And general other precautions .

    1. Hello Neha, I’d suggest you rest at Kaza for an extra day or get on to a dose of diamox (125 mg every 12 hours) starting from Manali till you come back to Manali.

    1. Hello Abby
      will you be trekking from Manali to Spiti? If not, then you can do without the diamox. But in case you are then resting at Kaza for 2 nights will do you good.

    1. Hi Aneesh,
      Which trek are you going on? What will be altitude range that you will be trekking in? For how many days out of the month will you be at altitudes above 11,000 ft?

  10. Hi Team,

    I am going to Kedarkantha trek staring on March 25th 2018 via India Hikes. Should I take Diamox as a precaution starting from tomorrow.

    Please advise.

    Sabarish J

    1. Hi Sabarish,
      You do not need to take Diamox in advance for the Kedarkantha trek. You can take it if you have any AMS symptoms during the trek, if your Trek Leader advises you to do so.

  11. Hi Swati/Arjun,

    I had been to Ladakh, Spiti in the past 2-3 years and everytime we climbed altitude, I was hit by AMS and pretty much reduced to being a luggage in the vehicle. I was planning to do my 1st trek at Chandernahan in this month (March-2018) and came across all the material put out by you guys. Started by reading the manual, prepping up with increased water consumption and also the diamox dosage 2-3 days before and during the trek.

    I write with utmost pleasure that I could complete the trek fully fit. Thank you for doing what you do best.


  12. I am 35 years old and serving in BRO n recently posted from Delhi to Lumla, distt Twang Arunachal Pradesh. I was reached at Lumla on 25th Mar at 2000 hrs by taxi after starting from Tezpur Assam. On arrival at there I faced the difficulty to taking breath and problem to sleep with suffering slowly chest pain. Next day I proceed to hospital for acclamation they given me dimox for one day and after that normal pain killer and rantadin. But some time I am suffering from chest pain and less sleep, after 4 days I came back to down for complete health check up. On arrival at my home town Bathinda Punjab I get checked up related heart and the all tests are normal. But I am suffering from chest pain some times. Now I will be again move to high altitude plz advice me for the same

  13. Hi,
    We are a family of 3 with son 15 yrs old. We are planning to Visit Srinagar for 2 Days followed by Leh for 5 days. When should we start Diamox? Should my son also take Diamox?

    Thanks in advance



    1. Hi Vasu,
      You can begin taking Diamox in Srinagar, from the morning before you depart for Leh. Your son can also take Diamox.
      The day you reach Leh, please rest in the hotel and do not do anything strenuous. You can plan a visit to the Leh market at most.

  14. I am going to MANSAROBOR with my wife on 24th June through NEPALGAUNJE,SIMIKOT,HILSA by FLIGHT. I am 59yrs.aged ( my weight is 75 KGS.) and age of my wife is 52 yrs. old and her weight is approx. 80 KGS.
    In between our this tour I also going to a PARIKRAMA of KAILAS PARVAT for 3Days.
    Now I asked to you about what type of PRECAution I have to take for a GOOD tour of our this said TOUR.
    Is it necessary to take DIAMOX tablet on REGULAR basis and then what is the DOSAGE ?

    1. Hello Mr. Banerjee,
      Going on a course of Diamox will be helpful. You can start after you reach Nepal. The dosage can be 125 mg twice a day.

  15. Hello India hikes, pls advise .
    I am arriving at leh on aug1st and am going for my FIRST pillion ride on aug2nd from Leh to Khardung pass n back to leh. next day plan is leh to Nubra Valley n next day back to leh . Am a person with traveling sickness n fibromyalgia . The total travel is four 5days as I am informed
    Kindly advise on a good precautionary plan, totally confused .

    1. Hi Sheena,
      Please spend at least 2 full days in Leh to acclimatise before setting out on the bike rides. On the day you arrive in Leh, take complete rest. At the most, you can go and stroll around in the market.

  16. We are planning a bike trip in this month from manali to Srinagar and the itenary is a follows:
    Day 1 – Manali
    Day 2 – Manali to Jispa
    Day 3 – Jispa to Tsokar
    Day 4 – Tsokar to Tso moriri
    Day 5 – Tso moriri to Hanle
    Day 6 – Hanle to Pangong
    Day 7 – Pangong to Nubra
    Day 8 – Nubra to Leh via Khardungla
    Day 9 – Leh to Kargil
    Day 10 – Kargil to Sonmarg
    Day 11 – Srinagar airport
    Kindly suggest whether the route given by the tour operator is okay Acclimatization and what precautions to be taken to avoid AMS

  17. I am traveling with a mission group to La Paz Bolivia the 21st of Sept. 2018. We will be staying in La Paz for a couple of days and then going on up 3,000 more feet into the mountains for one night to work with a group up there. We will not be doing a lot of strenuous work, mainly getting to know the ladies, crafts, and Bible studies. Do you feel we will need to take Diamox & if so when should we start it? All of the women in the group are over 60 and some in their 80’s.
    Thanks so much for your help.

  18. Does the diamox dosage depend on the weight of the person?
    What dosage of diamox should a male adult 6 feet 2 inches, weight 95 kgs . Planning to do EBC

    1. Hi Malvika, technically it does depend on the weight of the person. But most of the time, we usually go by whether the trekker is an adult or a child. The dosage for children (if at all, very rarely do we have to medicate children) is much lower. For someone of your body weight, it would really depend on the severity of the symptoms.

      If you’re taking Diamox as a preventive course, go for 125 mg every 12 hours. The EBC trek has enough days built in to acclimatise. So you should be fine with just that much dosage. If you feel mild symptoms any time, then take 250 mg (that’s a whole tablet).

    1. You need to drink that much water, whether or not you’re taking Diamox. It does make you more thirsty, that’s true. But that’s a good thing because it makes you hydrate yourself.

  19. I am a 45 yr old 95 kilo male who doesnt go to gym or do any long distance running or cycling..etc. Whenever possible – i.e.. 3-4 days a week, I walk one hour in the park covering 5 Km. With this kind of fitness, I did the Annapurna Base Camp couple of weeks back without any guide or porter, carrying a backpack of around 10 kgs and eating dal bhat for dinner and ready to eat Poha or aloo paratha for breakfast and normally skipping lunch. I walked 9-10 hours a day (Ghandruk – Chomrong – Dhoban – MBC – ABC (4200 metres) – Dhoban – 10Kms past Modki (trying to save jeep fare)). So I did the trek Pokhra to Pokhra in 7 days – and I did not face any issues and I was by far the slowest person since almost everyone on the trek seemed to overtake me.

    Of course how one reacts to altitude depends individual to individual. If one has the time and discipline to do Cardio and other such fitness regimens – great. If you dont – then you dont have to opt out of treks with the fear that you will be unable to complete.

    In fact I would highly suggest Annapurna Base Camp trek – better to go with Indiahikes or some group coz I felt bored many a days walkiing all alone without seeing another human for hours together some days.

    If I at almost 100 kilos and 45 years of age can do it without guide or porter – you can do as well. If you are short on time – Following plan will work very well (assuming you have a strict budget – if not you can directly fly Pokhara to your city in India). Cheapest way to do from Bangalore is as below:

    Saturday – early morning flight from BLR to Lucknow, then take a unreserved train to Gorakhpur, Shared taxi from Gorakhpur railway station to Sunaili, then bus to Pokhara. Flight is 3500, train is 110, Taxi is 250 and bus to Pokhara is 300 – all INR

    Sunday morning reach Pokhara – get Permit at local office, freshen up, have breakfast and take bus to Landruk and stay overnight. Expenses all in NPR – Food – 750, Permit – 1000, Bus/taxi – 500

    Monday – Trek from Landruk to Chomrong – Food and drink – 1000, Hotel – 200 – all NPR

    Tuesday – Chomrong to Dhovan – Food and drink – 1500, Lodging – 200 – all NPR

    Wednesday – Dhovan to ABC – Food and drink – 2000, Lodging – 200

    Thursday – ABC to Dhovan – Food and drink – 2000, Lodging – 200

    Friday – Dhovan to Landruk or Modki – Food and drink – 2000, Lodging 200

    Saturday – Pokhra to Gorakhpur – Food and drink – 1000, Lodging 300. Overnnight bus or train from Gorakhpur to Lucknow

    Sunday – Flight from Lucknow to bangalore.

    If one has 3 extra days – they can take train from BLR to Gorakhpur and back or go to Kathmandu.