Altitude Sickness
On this page
Symptoms of altitude sickness
Altitude sickness causes a range of symptoms which usually come on around 6-10 hours after being at a high altitude. Symptoms include:
- A headache (the most common symptom)
- Dizziness
- Loss of appetite
- Feeling sick or vomiting
- Feeling very tired, even when you’re resting
- Trouble sleeping
For most people, altitude sickness doesn't get worse than acute mountain sickness (AMS), the mildest form. If you get mild symptoms and stop going higher, they should get better and go away in a few days as your body adapts to the altitude you’re at.
Causes of altitude sickness
At higher altitudes, the pressure in the atmosphere lowers. That means there’s less oxygen available to breathe in, which your blood and organs need to function. When travelling to higher altitudes where there’s less oxygen in the air, your body needs to go through a process called acclimatisation to get used to the new environment. This usually takes a few days. Altitude sickness happens when you walk or climb higher up too fast, and your body doesn’t have time to acclimatise and get used to the change in pressure and oxygen levels.
Types of altitude sickness
Acute mountain sickness (AMS)
Acute mountain sickness (AMS) is the mildest form and is very common. It can become more severe as symptoms worsen.
High altitude cerebral edema (HACE)
High altitude cerebral edema (HACE) is a severe form of altitude sickness and is when your brain fills with fluid and swells. It can develop if you ignore the symptoms of AMS, and you must descend and get medical attention immediately.
High altitude pulmonary edema (HAPE)
High altitude pulmonary edema (HAPE) is another serious form of altitude sickness and is when the high altitude causes your lungs to fill with fluid. It’s dangerous and is the most common cause of death from altitude sickness. If it develops, you need to descend and get medical attention immediately.
Who can get altitude sickness?
Anyone can get altitude sickness, regardless of their age or fitness level – even athletes. Your risk of getting it actually depends on a few other things:
How high you travel
Altitude sickness becomes more common the higher you go. It’s very rare below 2500m, but almost everyone who goes above 3,352m will have some symptoms (mostly mild ones). You can’t get altitude sickness in the UK, but some destinations at a high altitude you’ll probably have heard of are Mount Everest in Nepal, Mount Kilimanjaro in Tanzania, and some cities in South America like Bogota.
How quickly you get there
People who fly to a high area are more likely to get altitude sickness than those who walk or climb. Above 2,500m, try not to sleep more than 500m higher than you slept the night before if you’re at 3,000m or higher, and take a rest every 3-4 days. This time allows the body to acclimatise.
Your history of altitude sickness
If you’ve had altitude sickness before, you’re more likely to get it again (especially if it was severe). It’s important you consider a slower ascent the next time.
Using drugs and alcohol
Drinking and taking certain medicines, particularly sedatives, can increase your risk of developing symptoms.
Although having certain illnesses like asthma or diabetes doesn’t automatically mean you’re more likely to get altitude sickness, some conditions make it harder to tolerate a high altitude, like sickle cell anaemia, heart failure or cystic fibrosis.
Treatment for altitude sickness
There are only two ways to ‘cure’ altitude sickness: rest or go to a lower altitude. If you get a headache and at least one other symptom within a day or two of going to a higher altitude, you could have altitude sickness. Mild AMS, symptoms usually go away on their own within 1 to 3 days if you rest and give your body time to adjust to the new altitude.
How to treat altitude sickness symptoms yourself
Here are some things you can do to help yourself if you notice symptoms. Some of these might also be helpful if you can’t go to a lower altitude easily or quickly:
- Stop and rest. Don't go any higher until the symptoms are completely gone
- Tell someone you’re travelling with that you’re not feeling well. They can help you manage your symptoms and stay alert to any changes
- Stay warm and drink plenty of fluids, but not alcohol
- Descend if symptoms worsen
- Take pain relief like paracetamol or ibuprofen, if appropriate
Medical treatment for altitude sickness
There are treatments available for altitude sickness that’s already started. Because altitude sickness can become dangerous quickly, it’s important to descend to stop the sickness from getting worse. You may also be able to access medical care more easily at lower altitudes. Depending on how severe the condition is, you may be given:
- Steroid medicine to delay the symptoms of more severe altitude sickness
- Medicine to lower your blood pressure and the pressure in your lungs
- Extra oxygen through a mask
- An x-ray of your chest, or a doctor might use a stethoscope
- An MRI or CT scan to check for fluid in the brain
In rare cases or in remote areas, you might get hyperbaric treatment. This is when you get oxygen from a special airtight chamber to increase the amount of oxygen in the blood.
If symptoms worsen, or they don't go away in a few days, descend to a lower altitude. It’s recommended to descend between at least 300m and 1000m, you should seek medical attention immediately.
Prevention
How to reduce the risk of getting altitude sickness
Travelling to places at a higher altitude can be a thrilling and challenging experience. To make sure you get the best out of yours, there are some things you can do to reduce the risk of getting altitude sickness.
Before you travel
It’s best not to smoke, drink alcohol, do vigorous exercise or take medicine like sleeping pills before you go especially for the first 48 hours of your journey. You can have caffeine if you normally drink it.
While you’re travelling
The best way to prevent altitude sickness while you’re on your journey is by giving your body time to get used to the higher altitudes as you travel and avoid going too high, too fast. Some steps you can take to do this are:
- Starting your journey below 3,000m (or around 10,000 feet). A good rule of thumb is to start from the altitude of the place you last slept. If you’re flying or driving somewhere higher, try to stop at a place lower for at least a day before carrying on
- Travelling to a higher altitude slowly. From 2,500m, it’s recommended that your sleeping altitude is no more than 300-500m higher each day. Also, for every 1,000m you climb, sleep at that altitude for at least one extra day
- Drinking plenty of water
- Keeping your sleeping altitude lower if possible. So you can climb high, but sleep low
- Walking slowly at the beginning of your journey
- Altitude sickness can happen in remote places where medical equipment isn’t easily accessible. You could consider taking supplemental oxygen and a portable hyperbaric chamber
The most important thing is to descend at least 500m lower down as soon as you can if you start to experience severe symptoms.
Medicine to prevent altitude sickness
You could take medicine before and during your trip to help your body get used to the higher altitudes quickly. Speak to your GP, or, you can visit Boots Online Doctor’s Altitude Sickness Treatment Service2 for quick, convenient access to advice and treatment if it's right for you. They’ll review everything within 24 hours and you could get your medicine within a few days.
Other things to think about at high altitude
The higher up you go, the higher the risk of sunburn and frostbite. To protect yourself, wear sunglasses with a UV filter, make sure you wear clothing that covers your skin, including your face, and use a sunblock with a protection factor of at least SPF30 – a higher protection sunblock is better for exposed skin like the lips, ears and nose. And don’t forget to stay warm and dry throughout your journey.
Related services
Advice for your upcoming adventure
Frequently asked questions
Altitude sickness is usually mild, with most people experiencing symptoms such as nausea, dizziness, or lightheadedness above 3000 metres. However, if you’re travelling to a high altitude, you should be aware of the signs and symptoms of severe altitude sickness.
If you experience difficulty breathing, chest tightness or pain, severe headache, vomiting, and/or confusion you should descend to a lower altitude immediately and seek medical help. If left untreated, severe altitude sickness can lead to swelling in your lungs or brain and can cause coma or death.
Symptoms of altitude sickness usually occur within 6 to 12 hours of reaching a high altitude. It’s also common for sleep to be disturbed at altitude. This improves as you become more acclimatised.
The best way you can avoid altitude sickness is by ascending slowly, giving your body time to adjust to higher altitudes over a number of days. There are also some small studies showing that practising deep breathing techniques can help you to breathe more efficiently at higher altitudes.
1Subject to availability. Eligibility criteria may apply. Charges may apply.
2Access to prescription-only treatment is subject to an online consultation with a clinician to assess suitability. Subject to availability. Charges apply.
9Eligibility criteria and charges apply. Available in selected pharmacies, subject to availability. A consultation fee may apply.
35For people aged two and over. Eligibility criteria apply. Subject to availability. Charges apply
