Altitude Sickness | Active ingredient(s): Acetazolamide | Manufacturer: Mercury Pharma

Recommended dose: one tablet, twice a day. Start treatment 2-3 days before your ascent.

Out of stock

Diamox is under review by our doctors and orders have been currently stopped. For more information on alternative treatments to altitude sickness, please visit our altitude sickness information page.

  • Review by a qualified doctor
  • Including prescription
  • Next-day delivery included

How does Diamox work?

Acetazolamide, the active ingredient in Diamox is a carbonic anhydrase inhibitor as well as a diuretic. This treatment aims to influence blood acidity levels. By doing this it can reduce the risk of symptoms such as headaches.

In addition to influencing blood-acidity levels, it also produces bicarbonate, which gives it its diuretic effect, thereby ensuring that the water levels in blood remain at a healthy level. Both these actions don't just help to reduce the mild discomforts associated with this condition but can also reduce the risk of a patient developing more serious complications.

Who should use Diamox?

Although generally safe to use, this can't be taken safely by everybody. People who should not use Diamox are those who are allergic or sensitive to the ingredient acetazolamide or any of the other ingredients contained in this medication. It's also unsuitable for pregnant or breastfeeding women to use, those with low blood potassium or sodium levels, patients with liver or kidney conditions or who have been diagnosed with Addison's disease, suffer from gout or have lung problems.

When completing your online consultation with 121doc, you should make sure that you provide us all the health information that is asked, as this will provide our doctor with the suitable data to make the best recommendation for you. our doctor will also want to be sure that you'll be using this treatment safely and not as an alternative to traditional acclimatisation measures.

How do you take this medication?

This medicine is available in a 125mg or a 250mg dose. The tablets should be swallowed whole, with a glass of water alongside a meal. The dosage that will be prescribed to you will depend on your individual needs and current health, although the traditional recommendation will be up to a maximum of four tablets a day. As it is a preventative treatment, you'll likely have to start taking your acetazolamide tablets a couple of days before you start ascending.

It is essential that you follow traditional methods for avoiding altitude sickness and that you don't change your dose without speaking to your doctor first.

What are the side effects of Diamox?

All prescription medications have a minor risk of side effects, but it doesn't mean that they will appear in everyone who uses this treatment. Side effects that have been reported are nausea, vomiting, dizziness or rash, but luckily these are mild and shouldn't be lasting. You should, however, be aware that one of the rare side effects of this treatment is an allergic reaction, for which you will need to seek immediate medical help.

How to order online

You can prepare for your climb by ordering Diamox safely from 121doc. Here we ask all our patients to complete a completely free and confidential consultation form, as this will allow our licensed doctor to provide a prescription based on your individual needs. This means that our doctor may choose not to provide you with a prescription if this is a safer option. If a prescription is issued, it will be sent straight to our pharmacy, where a registered pharmacist will dispense it. It will then be packaged and dispatched via secure courier service for next day delivery. All orders include a free consultation and there is no additional charge for delivery.

Note: You must complete a short online consultation so that our doctor can ensure that the treatment is suitable for you. The above pricing should only be used as a reference. The final decision to issue this treatment lies with the prescribing doctor.


What is included in the online consultation?
Will a doctor review my consultation?
What happens after I submit my order?
Is the price all-inclusive?
Can I place more than one order at a time?
What are my delivery options?
Is it safe to buy prescription medication online?
How do I know which treatment is best for me?
Is this service discreet?
What is included in the online consultation?

Our consultations include general questions about your health (e.g. blood pressure levels, current and past conditions), as well as specific questions related to your selected treatment. We will also request relevant personal information to complete payment and delivery.

All questions are necessary, and your answers and details will not be shared with any third-parties. Only our doctors have access to your medical information.

Will a doctor review my consultation?

It is a legal and medical requirement that a doctor first reviews all completed consultations. We have a team of in-house doctors and specialists who will ensure your selected treatment is safe for your use. All information is stored securely and confidentially.

Please note, we do not guarantee that our doctors will approve treatment.

What happens after I submit my order?

Your consultation will be sent directly to our medical team, where it will be reviewed by one of our doctors.

If your chosen treatment is deemed suitable for your use, they will issue a prescription. Your prescription is then forwarded to our pharmacy, where your medication will be dispensed and dispatched for courier delivery.

Is the price all-inclusive?

Yes. All 121doc orders include a medical consultation, a prescription and next-day delivery. There are no additional costs. We believe in providing a safe and easy-to-use service.

Can I place more than one order at a time?

Yes. However, certain medications may negatively interact with each other. Our doctors may not approve your order on this basis.

You can place multiple items in one basket, and complete a consultation for all.

If you wish to place a second order for a different medication, you will have to complete a separate consultation.

What are my delivery options?

We offer several delivery options:

  • Next-day delivery
  • UPS Access Point - convenient parcel drop-off and collection near your home or work address
  • Nominated-day delivery - choose the most convenient day for delivery

All these options can be tracked and require a signature on delivery. If you are not available, a friend or relative can sign in your place.

None of these options will incur an additional charge.

Is it safe to buy prescription medication online?

To ensure you are purchasing from a reputable company, you should look to see their country’s regulatory bodies verify them.

In the UK, this is the Care Quality Commission (CQC) and the Medicines and Healthcare products Regulatory Agency (MHRA).Certificates can be viewed here.

How do I know which treatment is best for me?

Some treatments also offer the 'Advise Me' function. You will be asked questions about your lifestyle and needs, plus medical questions. You will then be presented with the advice of our doctors.

Is this service discreet?

Our patients’ privacy is of utmost importance. All your medical information is securely stored and only viewed by our doctors. We do not share your details with third-parties. We are also regularly inspected by various UK regulatory agencies, such as the Information Commissioner's Office (ICO).

All orders will only show on invoices, bank statements, etc. as ‘HHC Ltd’.

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How does it work?

Select Select your treatment and complete our online consultation.
Free consultation


Select a condition here or use the top menu. For every condition, we provide you with information as well as the treatments we currently offer. If you don’t know which is best for you, just click the 'Advise-me' button.


If you know what you want, the quickest way to find a specific medication is to use the search bar here.


Every order starts with an online consultation. We will ask you medical questions to make sure only treatment that is safe and effective is prescribed. We take into account your lifestyle, health and any other medications you’re currently using.

The consultation is completely free, and takes between 5 and 10 minutes of your time.

All your information is safe with us. We don’t share it with anyone unless you want us to.


If you need any guidance, you can call, message or email our customer service team via the ‘How can we help you?' section here.

Prescribe Our doctors review your order.
Free prescription


As soon as you place the order, one of our doctors will review your consultation. On working days, this usually takes around one hour.


If the doctor has any additional questions, you will receive a phone call and an email. We understand you might be at work or busy. Our customer service representatives are always discreet and can call back at a more convenient time if necessary.

Our emails never contain any personal or medical information, only a link to your private account on our website (where you will find your messages).


Once our pharmacy receives your prescription, you will get a second email with your package tracking code.

Deliver Expect your delivery the next working day.
Always free. Discreet packaging.
Free next-day delivery


All orders include next-day delivery. Alternatively, you can select a delivery date that suits you better.


We also provide a free UPS Access Point service. Pick up your package from one of many collection points across the UK.

With your tracking code, you will know the estimated delivery time. All we need is your signature (or a friend‘s or relative’s).


All parcels are plainly labelled; there is no logo or any indication of its contents. Inside, you will find your treatment as well as a patient leaflet in your chosen language.

Repeat Subscribe and save with our repeat service. Never miss a dose again.
10 to 15% off


With 121doc’s Subscribe & Save service, you can automatically receive your treatment every few weeks or months.

The order will be generated by us, using the information you provided (including delivery frequency). You don’t have to do anything. Payment is taken two days before shipping.


There are two ways to subscribe. The first is during the order process. The second is via your profile here.

You can cancel or amend your repeat prescriptions at any time.


There are no sign-up fees with this service. Plus, you get a 10% discount off all future prescriptions, increasing to 15% after six orders!