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Altitude Sickness Tablets

Acetazolamide Tablets 250mg
Pack Size: 28 tablets
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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, lightheadedness, 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 until 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 acclimatised 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. 

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 Online Doctor Altitude Sickness page.

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

Azetazolamide 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 Azetazolamide 250mg tablets has been shown to cut recovery time in half (between 12-24 hours).

Taking Azetazolamide will help to decrease the likelihood of experiencing altitude sickness in people who are forced to ascend without the proper acclimatisation. However, Azetazolamide should not be seen as a substitute for acclimatisation. Rapid ascents can still carry dangers with or without Azetazolamide 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 Azetazolamide tablets will help improve this pattern of breathing, resulting in a better quality of sleep.

Azetazolamide used to be known as Diamox tablets. However, the brand Diamox has been discontinued. The medication has since been rebranded as Azetazolamide tablets, which was the same active ingredient found in Diamox. Azetazolamide 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. Azetazolamide 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. Azetazolamide is a prescription only medicine (POM). 

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.

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.
  • have lung problems.
  • have metabolic problems.
  • have salt and water imbalances.
  • have urinary problems.

About Altitude Sickness

Altitude Sickness Background

The Independent Pharmacy Online Doctor service allows patients who require a supply of altitude sickness medication to have a private consultation with a doctor and receive the treatment they require in a safe and discreet manner.

Altitude sickness (also known as acute mountain sickness) commonly occurs in climbers that reach a high altitude too quickly without time to adjust to the new environment. As altitude increases the atmospheric pressure decreases, meaning there is decreasing levels of oxygen in the air you breathe. This decrease in the amount of oxygen you are breathing in causes the symptoms of altitude sickness including headache, nausea, dizziness and exhaustion.

Altitude sickness is common amongst climbers and skiers who spend time at 2,500m (8,000 feet) above sea level. Symptoms tend to get more severe at altitudes of 3,600m (12,000 feet) or more. There is no specific demographic that is more likely to develop altitude sickness than others; it is not affected by age, sex, fitness or weight. Some people are more susceptible to getting altitude sickness than others, and it does not mean you will experience it in the future because you have had it previously.

Altitude Sickness Symptoms

At altitudes of 2,500m (8,000 feet) or higher, the symptoms of altitude sickness can appear within 6 to 24 hours if you have ascended the mountain to quickly.

The symptoms of mild altitude sickness include:

  • Headache
  • Nausea/vomiting
  • Dizziness/feeling unsteady
  • Tiredness
  • Loss of appetite
  • Upset stomach
  • Shortness of breath
  • Increased heart rate
  • Difficulty sleeping

There will usually be a general feeling of being unwell, like having a bad hangover. Normally the symptoms of altitude sickness are worse at night.

In more severe cases of altitude sickness the following symptoms may occur:

  • Persistent, irritable cough
  • Breathlessness
  • Bubbling sound in the chest
  • Coughing up pink/white frothy liquid
  • Difficulty walking/clumsiness
  • Irrational behavior
  • Double vision
  • Drowsiness
  • Confusion
  • Convulsions/fits

In addition to these symptoms, there may be a worsening of the symptoms of mild altitude sickness above. Severe symptoms of altitude sickness can be a sign of cerebral or pulmonary oedema (excess fluid in the skull/lungs) and is a medical emergency. You should descend immediately and seek professional medical treatment.

Altitude Sickness Diagnosis

Altitude sickness is normally self-diagnosed, or diagnosed by a peer, based your symptoms. If there is a medical professional on your trip, they will be able to diagnose altitude sickness and give advice on its treatment.

Remember: if you experience or suspect severe symptoms of altitude sickness, you should descend with a partner and seek immediate medical treatment.

Altitude Sickness Treatment

If you are experiencing symptoms of mild altitude sickness, do not ascend any further for at least 24 to 48 hours, until your symptoms have cleared. You may wish to descend up to 500m to help ease symptoms and speed up acclimatisation. If the symptoms of mild altitude sickness do not go away after 48 hours you need to descend by at least 500m (1,600 feet) and do not climb again until the have completely disappeared.

To aid acclimatisation and ease symptoms of mild altitude sickness:

  • Do not exercise
  • Keep hydrated
  • Avoid alcohol
  • Do not smoke
  • Do not use sleeping pills
  • Eat a high-calorie diet
  • Rest as much as possible

Always ensure you tell your group how you are feeling so they can be aware to look out for symptoms of severe altitude sickness.

Oxygen treatment can be helpful to ease symptoms of altitude sickness to allow you to descend and acclimatise. Oxygen treatment is not a replacement for descending and acclimatising.

Paracetamol or ibuprofen can be used to treat pain or discomfort from headaches caused by mild altitude sickness.

Promethazine (Phenergan) tablets can be used to treat nausea and sickness associated with mild altitude sickness. Promethazine is an antihistamine that also acts as anti-emetic (it stops nausea & vomiting).


Diamox (acetazolamide) can help to both ease the symptoms of, and prevent, mild altitude sickness. It helps to correct the chemical imbalance in your brain caused at high altitudes. Diamox can help to reduce the recovery time from mild altitude sickness from 24-48 hours to 12-24 hours, provided you do not ascend further in this time.

Diamox can also help to prevent altitude sickness in people who are ascending quickly without time to properly acclimatise. There is still however, the risk of serious altitude sickness if you do not properly acclimatise, which can result in a medical emergency. Rapid ascent is not recommended.

Diamox can occasionally cause mild side effects. These can include slight numbness or tingling in the face, fingers or toes, some loss of appetite, taste disturbance, flushing, thirst, headache, dizziness, fatigue, and irritability. Most doctors suggest taking a trial dose of Diamox for a couple of days before your trip to ensure you do not suffer any adverse reactions (this is normally half a tablet daily for 2-4 days).

Remember: even in those taking Diamox, 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 Diamox to push through the symptoms of altitude sickness and continue to climb, this is extremely dangerous and can be fatal.

Altitude Sickness Prevention

The most effective way to prevent altitude sickness at altitudes of 2,500m and above is proper acclimatisation. Climbing slowly will give your body proper chance to adapt to the changes in oxygen levels at high altitudes.

Rules to follow for proper acclimatisation:

  • Ascend slowly with overnight stops at regular intervals
  • Try to plan for days to acclimatise in your itinerary
  • If you are ascending over 3,000m (10,000 feet) you should spend at least one night at an intermediate level (1,500 – 2,000m) for a night before you start to ascend above 3,000m.
  • When ascending above 3,000m, only ascend 300-500m a day to each new overnight stop.
  • If more than a 500m ascent is necessary in a day, after the ascent you should descend back down so you are 500m or less from your original starting point that day. Your net increase in altitude should not be more than 500m without an overnight sleep stop.
  • For every 1,000m (3,000 feet) of ascent height, you should have 2 nights of sleep before going higher.

For walking or trekking holidays that involve climbing low peaks or crossing ridges but sleeping in valleys, altitude sickness is unlikely to be a problem. On skiing holidays where you are staying in a valley or sleeping at heights of 3,000m (10,000 feet) or less, altitude sickness is unlikely to be a problem. On climbing holidays where you will ascend to over 3,500m (12,000 feet) such as higher peaks in the Alps, Kilimanjaro and the Colorado Rockies, a few days spent climbing lower peaks to acclimatise is recommended.

Diamox (acetazolamide) can also be taken two days before, during your ascent and for one day after to help prevent altitude sickness.

To aid acclimatization, prevent and ease symptoms of mild altitude sickness:

  • Do not exercise
  • Keep hydrated
  • Avoid alcohol
  • Do not smoke
  • Do not use sleeping pills
  • Eat a high-calorie diet
  • Rest as much as possible

*RRP is based on the highest price found for a comparable online service found on 04/09/14.

The Independent Pharmacy is an online pharmacy and online doctor service is owned and operated by ABSM Healthcare Ltd (Company Reg. 08515600) and Red Label Medical Ltd (Company Reg. 08676338). All information that appears on this website is intended for information purposes only and should be used to supplement, not replace, your relationship with your local healthcare professionals. You should consult your doctor if you think you may have a health problem or before you start taking a new medicine. Please ensure you always read the information leaflets supplied with any medicinal products.For more information see our policies and terms and conditions at the bottom of every page. © 2014 ABSM Healthcare Ltd. All rights reserved.
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