Altitude sickness
Altitude sickness can occur when you travel to a high altitude too quickly.
Breathing becomes difficult because you aren't able to take in as much oxygen.
Altitude sickness, also called acute mountain sickness (AMS), can become a medical emergency if ignored.
Age, sex or physical fitness have no bearing on your likelihood of getting altitude sickness.
Just because you haven't had it before doesn't mean you won't develop it on another trip.
Symptoms of altitude sickness
Symptoms of altitude sickness usually develop between 6 and 24 hours after reaching altitudes more than 3,000m (9,842 feet) above sea level.
Symptoms are similar to those of a bad hangover.
They include:
- headache
- nausea and vomiting
- dizziness
- tiredness
- loss of appetite
- shortness of breath
The symptoms are usually worse at night.
It's not possible to get altitude sickness in the UK because the highest mountain, Ben Nevis in Scotland, is only 1,345m.