Symptoms of altitude sickness usually develop between6 and 24 hours after ascending to high altitude.
Common symptoms of mild altitude sickness (sometimes called acute mountain sickness) can be similar to a bad hangover and may include:
The symptoms are usually worse at night.
Signs of severe altitude sickness can include:
Severe symptoms could mean you're developing cerebral oedema or pulmonary oedema. These are potentially life-threatening complications of altitude sickness.
If you have symptoms of mild altitude sickness, don'tgo any higherfor 24 to 48 hours. If your symptoms don't improve or get worseduring this time, you should descend immediately.
Severe altitude sickness is a medical emergency. Someone with severe symptoms should immediately descend to a low altitude and seek medical help.
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.