Proper acclimatisation is the best way to prevent altitude sickness. Ascending slowly will give your body time to adapt to the change in altitude.
Before booking your trip, make sure there is enough time in the itinerary for acclimatisation so you do not put yourself at unnecessary risk of altitude sickness.
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.
Most walking, climbing or skiing holidays to the Alps involve sleeping in mountain huts at heights of around 3,000m above sea level, or the use of valley bases, and so severe altitude sickness is very unusual. However, acclimatisation for the higher mountains in the Alps will make a successful ascent more likely, and safer. Before setting out for peaks over about 3,500m, it is sensible to have spent a few days climbing lower peaks to gain acclimatisation.
It is 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.
Sleep at a lower altitude
Once you are above 3,000m (10,000 feet), do not increase the altitude at which you sleep by more than 300m a night. You can go up higher during the day, but each night go back down to a camp that is no more than 300m higher than the previous night's camp.
If this is not possible, some travel companies include a day’s rest in the itinerary, with a walk down the mountain to help you acclimatise.
Some holiday companies offer to let you climb a mountain in a short time, such as climbing Mont Blanc over a couple of days. If you are not already acclimatised, climbing at this rate is likely to lead to symptoms of altitude sickness. It would be better to do it at the end of a two-week holiday after you have acclimatised by climbing a few lower peaks first.
Medication
As well as being used to treat altitude sickness, acetazolamide (Diamox) and dexamethasone can also be used to prevent the symptoms.
Acetazolamide
For preventing altitude sickness, the recommended dose of acetazolamide is 125-250mg twice a day. Begin taking the medication one to two days before you start to ascend. Continue taking it while you are ascending and for three days after you have reached your highest altitude.
See Altitude sickness - treatment for more information about acetazolamide.
Dexamethasone
The recommended dose of dexamethasone is 4mg twice a day. It is usually taken for about two days, starting when you begin your ascent, to prevent the symptoms of altitude sickness developing.
See Altitude sickness - treatment for more information about dexamethasone.
Other preventative advice
As well as acclimatising properly and taking prescription medication, follow the advice below:
- If you start to develop moderate symptoms of altitude sickness, stay at your current altitude until your symptoms improve.
- If your symptoms get worse, immediately descend from your current altitude.
- As different people acclimatise at different rates, make sure that everyone you are travelling with has fully acclimatised before you go any higher.
- Keep well hydrated by drinking plenty of fluids (a minimum of four to six litres a day).
- While at altitude, eat a high-calorie diet.
- Do not smoke, drink alcohol or use medication such as tranquillisers and sleeping pills while you are at altitude. They could make any symptoms of altitude sickness worse. Speak to your GP if you are unsure.
- Remember that the risk of sunburn and sunstroke is increased at altitude, so take full precautions to prevent these happening. In particular, make sure you have appropriate eye protection (specialist sunglasses, snow goggles or equivalent) and use them, even if it is hazy, to prevent snowblindness.
