Altitude Sickness: All You Need To Know

If you're planning to trek in the Himalayas, the Alps, the Andes — or anywhere above 2500m — it's important to have a good understanding of altitude sickness, which poses a danger to everyone at these altitudes and can be fatal, in severe cases. The good news is that it's easily managed with the right planning and preparation.

Fast facts

  • Altitude sickness is also called Acute Mountain Sickness (AMS)
  • Altitude sickness can occur anywhere above 2500m
  • Hire an experienced guide who understands how to handle AMS
  • Avoid sleeping more than 300m above the previous night's altitude
  • Everyone adjusts to altitude differently; listen to your body!
  • Make sure your travel insurances covers high-altitude rescue
  • Don't be afraid to turn around – trying to overcome your symptoms can turn simple situation into a bad one very quickly

What is Altitude Sickness?

At high altitude, there is less available oxygen so your heart and lungs have to work harder, even at rest. Add the strenuous exercise of climbing a mountain trail and your body is under serious strain. As you go higher, this effect becomes increasingly severe. Your body needs time to adapt and this is called ‘acclimatising’. If you ascend faster than your body acclimatizes, you will develop AMS. Not responding appropriately can be fatal.

Common Symptoms of AMS

Everyone responds to altitude differently. While most people don't feel the effects until around 2500m, some may feel the effects a bit below that altitude. Some people may acclimatize quickly and will be able to ascend more quickly, others may simply not acclimatize at all. It is critically important to listen to your body, rather than try to fit in with the group or stick to the itinerary.

Early/mild symptoms

A headache (typically throbbing, often worse for bending over or lying down), plus one or more of the following symptoms:

  • Tiredness, weakness
  • Dizziness, lightheadedness
  • Loss of appetite, nausea
  • Insomnia, disturbed sleep, frequent waking, irregular breathing and waking with gasping intake of breath

These early symptoms can also look like dehydration and excess exercise or excess sun exposure. It’s critical that you keep hydrated, protected from the sun and pace yourself, so you don’t mask AMS symptoms.

If untreated, then mild AMS can progress to cerebral edema or pulmonary edema. Both can be fatal and it is critical that you treat the early symptoms. You should also learn the symptoms of more serious AMS, so please do the research before you go.

Children at high altitude

With children, you need to pay extra attention at altitude given that children are less able to recognize and communicate the symptoms of AMS. For pre-school children (aged 3-5), it is generally recommended to sleep no higher than 3000m and to preferably sleep below 2500m. For children 8 years and older, it is assumed that altitude symptoms will occur in much the same way as it does in adults, but again, they may not always be able to communicate these symptoms.

Should any signs of illness or discomfort occur at altitude with your children, it's safest to assume these are altitude-related and descend immediately depending on the severity of the symptoms. For more information, please check out this article on trekking with Children at High Altitude.

How to prevent AMS?

You need to make sure your itinerary has a safe rate of ascent and allows for adjustments to be made in case one or more of the group does not acclimatize adequately.

Expert recommendations

  • Above 2500m, sleep no higher than 300m (1000ft) above the previous night and have a rest day every third day up to 3500m (11,500 ft)
  • Above 3500m, only go up to 150m (500ft) per day with a rest day every three days

Preventative measures

  • Walk at a steady ‘plod’ and take regular breaks
  • Drink enough to keep your urine ‘pale and plentiful’. This may mean drinking 4-6 liters a day (as water, tea, soup, etc.)
  • Avoid sedative drugs (antihistamines, sleeping pills, etc.) as they suppress respiration and increase the risk of AMS. (This includes alcohol)
  • If you need to take any medication (eg. because you have an allergic reaction), then discuss this with your guide and manage the increased risk of AMS
  • Remember the symptoms – listen to your body and keep an eye on your fellow trekkers
  • Talk to the guide and follow their advice – severe AMS will reduce your ability to understand what is happening and sometimes the only option is to turn around and descend. Not following the expert advice will put your life in danger as well as others

If you develop any AMS symptoms, you must speak up. You need to get help and adjust the itinerary to allow your body to acclimatize safely.

Planning for a safe trek

Consult your doctor about trekking at altitude. If you take any medications, be sure to check how they may interact with altitude medication (eg Diamox) in case you need to take any. Be sure to advise your trek operator about any medications you take.

Also, make sure you go with an experienced trek operator and guide and ask them the following questions:

  • How does the itinerary allow for proper acclimatization?
  • What is in the first aid kit?
  • What is the training and experience of the guide and support team?
  • What precautions do you take to avoid an emergency situation from developing?
  • Should an emergency develop, what is your emergency response plan?
  • How will the guide manage an AMS patient who does not want to turn around and go down?

Remember, if you know the risks, symptoms, and treatments then you can plan for a safe trek and it will be the experience of a lifetime!

Don’t hesitate to ask any of the KimKim high altitude trek specialists about how to plan a safe high altitude trek. We are passionate about incredible journeys that do not compromise safety.