Buy Acetazolamide 250mg Tablets online

Acetazolamide 250mg Tablets (28 tablets)

Order before 4pm for delivery from Tue. 24 Apr.

Description for Acetazolamide 250mg Tablets

Acetazolamide is the generic version of the branded treatment Diamox (discontinued). It is prescribed by The Independent Pharmacy Online Doctor to prevent and treat altitude sickness in those ascending above 2,500 - 3,000m. 

Product Information

  • Age: 18 Years +

    Maximum per order: 2

  • Pregnancy: N/A

    Breastfeeding: N/A

Acetazolamide 250mg tablets (also known as Diamox) are available to buy from The Independent Pharmacy Online Doctor service, following a free consultation, to help to prevent and treat altitude sickness. To find out more about acne and see all the available treatments, see our Altitude Sickness page.

Acetazolamide has several applications but is widely prescribed 'off-label' to prevent or reduce the symptoms of altitude sickness. Acetazolamide can actively reduce nausea, dizziness, headache and shortness of breath associated with rapid ascents (usually anything above 10,000 feet or 3,048 metres).

Click here to read studies on the effectiveness of Acetazolamide in treating Altitude Sickness 'off label'. 'Off label' means that the medicine is being used to treat a condition other than those that it was initially licensed to treat. This means that there is less established data regarding the effectiveness of this treatment for the condition which it is prescribed and means that the instructions contained in the product information leaflet will not match the condition you are treating. You should always follow the instructions on the dispensing label on your medicine and contact us if you have any questions.

Acetazolamide 250mg tablets works to treat altitude sickness by increasing the amount of urine produced, consequently altering the acidity of the blood. This leads to a reduction in fluid in the lungs and around the brain. The result is improved breathing and relief from the symptoms of altitude sickness.

Without medication, the symptoms of altitude sickness will usually subside in around 24-48 hours if the proper procedures are followed. Taking Acetazolamide 250mg tablets has been shown to cut recovery time in half (between 12-24 hours).

Taking Acetazolamide will help to decrease the likelihood of experiencing altitude sickness in people who are forced to ascend without the proper acclimatisation. However, Acetazolamide should not be seen as a substitute for acclimatisation. Rapid ascents can still carry dangers with or without Acetazolamide usage.

Sleeping at altitude alters a person’s breathing patterns. It is usually characterised as short, rapid breaths followed by prolonged pauses. This is quite normal and is not considered dangerous. However, it can lead to a poor quality of sleep. Taking Acetazolamide tablets will help improve this pattern of breathing, resulting in a better quality of sleep.

Acetazolamide used to be known as Diamox tablets. However, the brand Diamox has been discontinued. The medication has since been rebranded as Acetazolamide tablets, which was the same active ingredient found in Diamox. Acetazolamide belongs to a category of medicines called diuretics. A diuretic is any substance that increases the production of urine, thus promoting the excretion of water from the body. Acetazolamide is manufactured by MercuryPharma. The tablet itself is white, round and convex with “FW 147” marked on one side. The other side of the tablet is scored into quarters. Acetazolamide is a prescription only medicine (POM). 
The majority of trekkers and climbers do not need to take Acetazolamide tablets (Diamox). Whilst altitude problems are unlikely below 2,500 metres (8,000 feet), it should be noted that anyone can suffer from altitude sickness, there is not a predisposing type and no-one is immune from it.

How to reduce the risk of altitude sickness

There are various ways to minimise the risk of altitude sickness by following established protocols which are:-
Acclimatise by ascending slowly with overnight stops at regular intervals.
If you are planning to climb over 3,000 metres (10,000 feet) you should plan to spend a night at an intermediate elevation which is below 3,000 metres before starting your ascent.
When reaching levels above 3,000 metres, only ascend a rate of 300-500 metres (1,000-1,500 feet) per day and then stop at your next sleep height.
For every 1,000 metres (3,000 feet) of ascent, plan to stop for two consecutive nights sleep before climbing any higher.
If you plan to climb more than 500 metres (1,500 feet) during one day, then descend back 500 metres to sleep.
Symptoms of mild early acute mountain sickness

If you experience any or all of the following symptoms, you should stop ascending until you feel better. These symptoms may include:-
Headache not relieved by Paracetamol and drinking water.
Fatigue and general weakness.
Dizziness and a feeling of being light-headed.
Difficulty sleeping.

If you develop any or all of these symptoms you should stop ascending until they have passed; most symptoms usually resolve within twenty-four to forty-eight hours. If you descend the symptoms may disappear more quickly. It helps to drink plenty and always avoid alcohol and sedatives. Ascent can continue when the symptoms have passed.

Emergency situations requiring immediate descent

There are two situations where immediate descent must be made to prevent danger to life and these are:-
1.Fluid on the lungs
The symptoms for this are loss of breath, difficulty breathing, extreme fatigue, breathing which has a rattling, noisy sound, repeated coughing, blue or grey lips and fingernails, drowsiness, collapse and confusion. This condition is known as HAPE (High Altitude Pulmonary Oedema). The key feature is an extreme shortness of breath – essentially being short of breath when everyone else has got their breath back.

2.Fluid on the brain
The symptoms for this may include lethargy, changes in behaviour and loss of coordination (inability to walk in a straight line). The key feature is cognitive impairment – an inability to think straight and carry our normal tasks. This condition is known as HACE (High Altitude Cerebral Oedema) and can progress to coma and death.

HACE and HAPE are both medical emergencies requiring immediate descent even if this is at night. The descent needs to be at least 500-1,000 metres (1,500-3,000 feet) and as soon as possible. Delay can be fatal. Further treatment may include oxygen, steroids and hyperbaric oxygen which is oxygen delivered in a high-pressure chamber but immediate descent remains imperative.

Key points to note about HACE and HAPE

Both conditions can be rapid onset and so can occur without warning.
Both conditions can develop rapidly over a period of hours.
HACE and HAPE most commonly start at night although they can come on in the day.
There may be no preceding symptoms or warnings.
Both conditions can affect people who have previously ascended to the same height without any problems.
These conditions can affect people who have followed the guidelines for acclimatisation.
HACE and HAPE can affect people who have been prescribed Acetazolamide.
The conditions can affect both fit and unfit people alike and also people indigenous to the area including mountain guides.

Alternative techniques if Azetazolamide is not available: 

Try to stay as hydrated as you possible can and avoid alcohol. Do not smoke and avoid using sleeping pills. Try to consume a high calorie diet whilst at altitude and when you can, rest as much as you possibly can. If you are experiencing symptoms of mild altitude sickness, refrain from ascending any further for at least 24 to 48 hours, until symptoms have cleared. It may help to descend up 500m to help ease symptoms and speed up the process of acclimatisation. 

*Prescription medicines are supplied subject to a medical consultation at the discretion of a doctor.

The dose of Acetazolamide will depend on how severe your mountain sickness is and the symptoms you are experiencing. You or a member of your group will need to decide on the most appropriate treatment. If you have a doctor or other healthcare professional on your trip, you should seek their advice. 

1. For the treatment of mild early acute mountain sickness (headache, fatigue, light headedness, difficulty with sleep): Acetazolamide 250mg (one tablet) twice daily until symptoms resolve, when planned ascent can be resumed.

2. Where rapid ascent without proper acclimatisation cannot be avoided: Acetazolamide 250mg (one tablet) twice daily, started the day before ascent or as soon as possible after starting to ascend and continue for 2-3 days after final altitude is reached.

3. For disturbed breathing pattern during sleep: Acetazolamide 125mg (half a tablet) twice daily. Continue descent to an altitude where sleep is no longer a problem.

Remember: even if you take Acetazolamide, it is still important to properly acclimatise. You should never ascend further until your symptoms have completely gone and you are properly acclimatized to your current altitude. Do not use Acetazolamide to push through the symptoms of altitude sickness and continue to climb, this is extremely dangerous and can be fatal. 

The following side effects can occur when taking Acetazolamide:

Dizziness, lightheadedness, and an increased amount of urine, blurred vision, dry mouth, drowsiness, loss of appetite, stomach upset, headache and tiredness.

These side effects are most likely at the start of treatment as your body gets used to the medicine. 

Tell your doctor immediately if any of these very unlikely but serious side effects occur: increased body hair, hearing loss, ringing in the ears, unusual tiredness, persistent nausea/vomiting, severe stomach/abdominal pain.

Seek immediate medical attention if any of these unlikely but very serious side effects occur: easy bleeding/bruising, fast/irregular heartbeat, signs of infection (e.g., fever, persistent sore throat), mental/mood changes (e.g., confusion, difficulty concentrating), severe muscle cramps/pain, tingling of the hands/feet, blood in the urine, dark urine, painful urination, yellowing of the eyes/skin.

A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include:blisters/sores in the mouth, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

If you experience any adverse effects from taking Acetazolamide it is important your trip doctor know immediately. In a medical emergency you should contact the emergency services or go straight to a hospital or medical centre.


Each tablet contains the active ingredient acetazolamide 250mg.

It also contains: lactose monohydrate, corn starch, gelatin, glycerin, water, talc,sodium starch glycolate type A potato, magesium stearate.

Acetazolamide is not suitable for use if you:

  • Are allergic or sensitive to or have had a bad reaction to sulphonamides in the past.
  • Are elderly.
  • Have adrenal gland problems.
  • Have chronic obstructive pulmonary disease.
  • Have closed angle glaucoma.
  • Have had kidney stones.
  • Have kidney or liver problems.


We offer FREE standard tracked delivery on orders over £40.

The following delivery options are available:

  • Standard Tracked Delivery - 2/3 day delivery - £2.95
  • Express Tracked Delivery - 1/2 day delivery - £4.45
  • Special Delivery (Guaranteed before 1pm) - £8.95
  • Saturday Guaranteed before 1pm - £10.45

All our orders are sent out using Royal Mail. We always aim to dispatch all orders received before 4pm the same working day. Any orders received after 4pm or over the weekend will be dispatched the next working day. Orders will not be dispatched on weekends or bank holidays.

All orders can be fully tracked in your account.

We ensure all parcels are in plain packaging for discreet delivery of your medicines and pharmacy goods.

Deliveries containing pharmacy-only or prescription medicines may require a signature on receipt. 

Delivery is free for all NHS prescriptions.

Please note: Royal Mail do not deliver on Sundays or Bank Holidays - this should be taken into account when ordering. 

If you are not home to accept your delivery, a card should be left by the Royal Mail representative. This card will provide details of where you can collect the order or how to arrange re-delivery.

Should you be unable to collect your missed delivery or arrange for your medication to be redelivered by Royal Mail, the pharmacy can resend your medication to the same, or a different address provided it has been returned to us and this happens within a 30 day window.

Once a package has been shipped with Royal Mail we advise that you are bound to the terms and conditions of their use together with the terms and conditions contained herein.

You have the right to cancel your order up to the point when your treatment is dispatched. The pharmacist must destroy any medication within 30 days of it being returned, even un-opened boxes, so we are not able to offer refunds once your treatment has been dispatched.


BFPO Postcodes

Unfortunately we are unable to deliver medicines to BFPO postcodes.


Remote Areas

Please be aware that Royal Mail Guaranteed services are not available to all customers in the UK, especially those that live in remote postcodes. Royal Mail advise customers of the following:

We deliver by 5.30pm the next working day in the following postcode areas:
AB30 - 39, 41 - 45, 51 - 56
GY9 Alderney (Channel Islands)
HS1, 3 - 9
IV21 - 28, 40 - 49, 51 - 56
KA27, 28
KW1 - 3, 5 - 15
KW16 Stromness Town only
PA20 (0&9)
PA28 - 38, 41 - 49, 76, 77
PH15, 17 - 26, 31 - 40, 49, 50


We deliver within two working days by 5.30pm to the following postcodes areas:
GY1 Herm (Channel Islands)
GY9 Sark (Channel Islands)
PA60 - 75, 78
ZE2, 3


We deliver within three working days by 5.30pm to the following postcode areas:
KW16 - non-Town
PH30, 41 - 44


Please note: This applies to our 'Special Delivery' and 'Saturday Guaranteed' services.



We are currently unable to ship orders outside of the UK.

We are unable to ship orders to mailing or forwarding houses for onwards shipping to locations outside of the UK.

Need to know more about Altitude Sickness?

Visit our advice area or contact our support team

Acetazolamide 250mg Tablets Reviews

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Frequently Asked Questions

  • How does Acetazolamide work?

    Acetazolamide is a prescription medicine which inhibits an enzyme in the body called ‘carbonic anhydrase’ slowing down certain chemical reactions in the body. Acetazolamide or Diamox increases the amount of urine produced by the body and changes the acidity of the blood. The net result of this is an improvement in breathing and a reduction in fluid around the brain and in the lungs. It is very important to drink plenty of fluids whilst taking Acetazolamide, at least two to three litres of water per day.

  • Can I keep climbing if I take Acetazolamide?

    Taking Acetazolamide for initial symptoms should not be viewed as a green light to keep climbing. Any ascending should cease until the symptoms have completely resolved which in most cases, is within twenty-four to forty-eight hours. Acetazolamide will not protect you against your symptoms worsening if you continue to ascend; plenty of climbers who have done this have gone on to develop either HAPE or HACE.

  • Will Acetazolamide protect me from altitude sickness if I take the tablets during rapid ascent?

    Acetazolamide will help reduce the risk of altitude sickness on rapid ascents; however it is not a substitute for following proper protocols and correct precautions. Rapid ascents carry serious risks and Acetazolamide does not remove these risks rather, use of it may encourage the climber to continue so that when illness strikes, it may be sudden, severe and possibly fatal.

  • I am really fit and strong so surely I won’t suffer with altitude sickness?

    Treat altitude with respect and do not imagine that you can simply battle through because you are strong and fit. People who climb and hike in high places have a reputation for pushing themselves. When it comes to altitude, preparation, planning ahead, taking one’s time and listening to one’s own body are the key virtues.

  • If I take Acetazolamide, will it mask a severe underlying condition leading to more serious health consequences?

    Acetazolamide does not mask serious underlying symptoms; the medication treats the cause not the symptoms. Acetazolamide accelerates acclimatisation. As acclimatisation occurs, the symptoms will resolve. Acetazolamide does not mask anything; if you are still unwell then your symptoms will persist despite the medication.

  • Will my symptoms get worse if I stop using Acetazolamide?

    Acetazolamide treats the cause not the symptoms of altitude sickness; when you stop taking the medication, the symptoms will not be any worse than if you had refrained from taking any medicine in the first place. If you feel better when you are taking Acetazolamide it is because your underlying condition has improved. If you stop taking Acetazolamide, then your acclimatisation will slow down to your own intrinsic rate, enabling you to gauge how well your recovery is progressing.

  • What are the benefits of Acetazolamide tablets?

    Even in its mildest form, altitude sickness can have a very negative impact on what should otherwise be an enjoyable experience. In severe cases, it can put your health at serious risk, sometimes even requiring hospitalisation. Acetazolamide tablets such as Diamox can help to prevent altitude sickness from occurring and they are also beneficial for mountain sickness, provided they are used in conjunction with appropriate precautionary measures such as acclimatisation.

  • Are Acetazolamide tablets suitable medication for me?

    Acetazolamide is classed as a ‘sulphonamide derivative’ so if you are sensitive to sulphonamides, you should not take this medication. There are other conditions and some prescribed medications which are not compatible with Acetazolamide so you should consult your Doctor before taking this medication and read clearly all of the warnings contained within the product literature.

  • Can I take Acetazolamide tablets and still drink alcohol?

    Yes you can drink alcohol whilst taking Acetazolamide tablets but it is not advisable if you are experiencing the symptoms of altitude sickness. Alcohol can make the symptoms of altitude sickness worse.

  • Can I drive whilst I am taking Acetazolamide tablets?

    Yes you can drive and take Acetazolamide tablets, however if you notice any adverse reactions or side effects, you cease taking the medication and discuss the symptoms with your doctor.

  • Can I buy Acetazolamide tablets over the counter?

    Acetazolamide  tablets are a prescription only medicine so you cannot buy them over the counter from your pharmacy before you go on holiday. Allow enough time to make an appointment with your GP or use our on line service which can issue you with a doctor-verified prescription based on your responses to our health questionnaire.

  • How do I store Acetazolamide tablets?

    Acetazolamide tablets come in a handy 250mg size making them very easy to store and take whilst on the move. It is recommended that you store the tablets in a safe and secure environment at a temperature below thirty degrees centigrade, preferably at room temperature. Always keep Diamox tablets out of the reach of children.

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