Proper acclimatisation to altitudes of 2,500m (just over 8,200 feet) or above is the best way to prevent altitude sickness. Ascending slowlywill give your body time to adapt to the change in altitude.
When booking a trip yourself, try to include two or three days to acclimatise. If you're booking a package holiday, check the itineraries of different providers to find a package that allows a few days for acclimatisation. If possible, you should try to avoid flying directly to a high altitude.
Some itineraries are more likely to cause problems with acclimatisation than others.For example, a trekking holiday that involves crossing ridges or low peaks but sleeping in the valleys is less likely to give rise to problems with altitude sickness than a climb up an isolated peak such as Kilimanjaro.
It's unusual to get severe altitude sickness during mostwalking, climbing or skiing holidays to the Alps. Overnight accommodation is usually in valleys or mountain huts at heights of around 3,000m (9,842 feet) above sea level.
However, acclimatisation for the higher mountains in the Alps will make a successful ascent more likely and safer. Before setting out for peaks over 3,500m (11,482 feet), it's sensible to have spent a few days climbing lower peaks to acclimatise.
It's not only on trekking or climbing holidays that high altitudes are reached for example, some parts of the Colorado Rockies can be reached by road despite being over 3,500m.
Once you'reabove 3,000m (10,000 feet),don't increase thealtitude at which you sleepby more than 300-500m a night. You can go up higher during the day, but each night go back down to a camp that's no more than 300-500m higher than the previous night's camp.
Someholiday companiesoffer trips to climb a mountain in a short space of time, such as climbing Mont Blanc over a couple of days.If you're not already acclimatised, climbing at this rate is likely to lead to symptoms of altitude sickness. It would be better to attempt the climb at the end of a two-week holiday after you've acclimatised by climbing a few lower peaks first.
Medicines would normally only be considered for preventing altitude sickness if rapid ascent cannot be avoided.
Research has shown that acetazolamide (Diamox, which is licensed to treat glaucoma) can help prevent symptoms of altitude sickness. It's thought that acetazolamide works by correcting the chemical imbalance of the blood,caused by ascending quickly to high altitude.
In the UK, acetazolamide is not licensed for preventing (or treating) altitude sickness. However, it may sometimes be considered for 'off-label' use to prevent altitude sickness in people who may be at risk of developing it. You should begin taking the medication one to two days before you start to ascend and continue to take it while ascending.
You may also be advised to take it for a day or two after you've reached your highest altitude. If you feel unwell while you're ascending, acetazolamide will not prevent you feeling worse and the only treatment is to descend or to rest.
There are a number of common but minor side effects associated with acetazolamide, including numbness or tingling of the face, fingers or toes. Some people find these quite distressing, so doctors often suggest trying it at home for two days before travelling if you're likely to use it at altitude.
You should let your doctor know if you have any allergies to any medicines before acetazolamide is prescribed. Your doctor will also check your medical history to see if acetazolamide is suitable for you.
Dexamethasone isn't usually recommended for preventing altitude sickness, but may be provided for the emergency treatment of high altitude cerebral oedema (HACE).
As well as acclimatising properly and takingprescription medication, you should also follow the advice outlined below.
Find out what to do if you have symptoms of altitude sickness, who's affected, and how you can prevent it.
Find out about the symptoms of mild and severe altitude sickness, which include headache, dizziness, nausea and vomiting, shortness of breath, and an increased heart rate.
Find out how altitude sickness should be treated, including descending to a lower altitude, oxygen treatment, and different types of medication.
Altitude sickness can cause potentially life-threatening conditions that affect the brain or lungs. Find out what to do if someone has severe symptoms of altitude sickness.
Find out how to prevent altitude sickness, including climbing slowly, particularly at altitudes of 2,500m or above. Ascending gradually will give your body time to adapt.
Jessica Mathur, a GP from London, was surprised when she became ill with altitude sickness during a holiday in Peru.