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Learning About Altitude Sickness

What is altitude sickness?

Altitude sickness occurs when you cannot get enough oxygen from the air at high altitudes.

It happens most often when people who are not used to high altitudes go quickly from lower altitudes to 2,500 metres (8,000 feet) or higher. When you go too high too fast, your body cannot adjust.

Altitude sickness can range from mild to life-threatening. With good planning, such as ascending slowly or taking certain medicines, it is often preventable.

What are the symptoms?

The symptoms of altitude sickness may be mild to severe. Symptoms may include:

  • A headache, which may get worse during the night and when you wake up.
  • Weakness.
  • Feeling sick to your stomach. You may vomit.
  • Feeling dizzy.
  • Being confused.
  • Breathing problems.

When altitude sickness is severe, it may be deadly.

Your symptoms may not start until a day after you have been at a high altitude. Many people say altitude sickness feels like having a hangover.

How can you prevent it?

You may be able to prevent altitude sickness by taking your time when you go to high altitudes and using medicine in advance.

  • If you go to altitudes higher than 2,500 m (8,000 ft), try to spend at least a night at a medium altitude before going higher. For example, in Canada, spend a night in Banff before going to the Rocky Mountains.
  • Do not fly into high-altitude cities. If this is not possible, avoid large meals, alcohol, and being very active after you arrive. Rest, and drink plenty of liquids. If you have symptoms, do not go higher until they have gone away.
  • Sleep at an altitude that is lower than the altitude you were at during the day. For example, if you ski at 3,000 m (9,500 ft) during the day, sleep the night before and the night after at 2,500 m (8,000 ft).
  • You may consider taking medicines such as ibuprofen, acetazolamide, or dexamethasone before travelling to high altitudes. These medicines may prevent or lessen symptoms. Talk to your doctor about this.

How is altitude sickness treated?

  • Go to a lower altitude. This is the best treatment for altitude sickness.
    • If you have mild symptoms, you may be able to stay at that altitude and let your body get used to it.
    • Go down at least 500 metres if your symptoms are moderate to severe, they get worse, or treatment with medicine or oxygen does not help.
    • Go to a lower altitude as fast as you can or get emergency help if someone with you has severe symptoms such as being confused or not being able to walk straight. Go with the person. Never let someone with severe altitude sickness go down alone.
  • If you stay at a high altitude, rest. Limit any walking or activity. Drink plenty of water, but do not drink alcohol. Do not go to a higher altitude until your symptoms go away. This may take from 12 hours to 3 or 4 days.
  • Your doctor may recommend dexamethasone to treat altitude sickness. Take it as directed.
  • Take an over-the-counter pain medicine, such as acetaminophen (Tylenol), ibuprofen (Advil, Motrin), or naproxen (Aleve). Read and follow all instructions on the label.
  • If available, you may also be able to use oxygen or a specially designed pressure chamber to treat altitude sickness.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

Where can you learn more?

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