During your stay in Colombia you might get the chance get to spend a few hours or a few days in altitude (above 2,500 meters). This information is for you!

Mountain Sickness (AMS or Altitude Sickness)

At altitude, the atmospheric pressure decreases: there is less oxygen available to the body. The amount of oxygen available at 3000 metres is two thirds of that available at sea level. At 5,000 metres, it is half as much.

The body reacts to this lack of oxygen (or hypoxia) in two ways:

Immediate reaction

Acceleration of ventilation and heart frequency in order to capture more oxygen from the air and transport it more quickly to the organs. This reaction costs energy to the body because it makes the respiratory muscles and the heart work harder.

Gradual response

The immediate reaction is replaced or supplemented by a more economical mechanism: the increase in the number of oxygen carriers, i.e. red blood cells. They take a long time to produce, you have to spend at least a week at altitude to see their numbers increase. The ventilation and heart frequency can then slow down, without returning to initial values.


Who is affected?

Altitude sickness (or “sorojche” in the Andes) is considered to affect about:

  • 15% of the people from 2,500 metres upwards
  • 60% of the people from 4,000 metres upwards
  • everyone in high altitude (over 5,000 meters)


What are the symptoms?

The reaction to altitude is specific to each individual. Most of the time, the AMS is benign and results in various disorders that occur separately or in combination with others, from the first hours of a stay at altitude:

  • headaches
  • feeling tired and drowsy
  • shortness of breath
  • sleep problems
  • dizziness and balance problems
  • loss of appetite and digestive problems
  • nausea
  • irritability
  • difficulty with urination


These symptoms, which are frequent and normal, generally disappear on their own (or at least greatly reduce) after a few hours at altitude and with the use of analgesics (aspirin or paracetamol).

In some cases, serious complications may occur: pulmonary edema (cough, sputum, blue lips, respiratory failure) or cerebral edema (severe headaches not relieved by aspirin, vomiting, visual disturbances, sometimes psychiatric disorders).

This is an extreme form of AMS and should be treated immediately:

  • by bringing the person suffering from the disease down to the lowest altitude without delay.
  • by consulting a specialized doctor

We experience a severe case of crisis about every two years (it usually occurs in the first few days at altitude). Our teams of guides and escorts are trained to diagnose swellings when they occur, and to react in the most appropriate way.

Before Departure

Physical training before a stay at altitude does not protect against altitude sickness, but is obviously desirable: cycling, swimming or hiking (if possible at high altitude) would be good preparation. Consult your doctor so that he or she can detect any deficiencies or affections.

Possibly consult a center specialized in mountain medicine.

For a stay including sports activities (trekking, mountain climbing …) above 3,000 meters, we will ask you to fill out a health questionnaire: depending on the answers you provide, we will ask you to present a certificate, issued by a doctor, declaring you fit to practice sports activities at altitude.

On site

To mitigate the effects of MAM, and limit the risks of aggravation, two golden rules must be respected.

Start slowly

One week at altitude is usually enough for a good acclimatisation. We take particular care to ensure that our programs start off slowly, with activities or excursions in the first few days that are not demanding, close to the health centres if necessary, and with plenty of rest areas.

Gradual ascent

It is advisable, beyond 3,500 metres, not to climb more than 700 metres from one night to the next. For example, starting at 3,500 metres, it is possible to climb a pass at 4,500 metres (+1,000 metres) if you sleep lower, for example at 4,000 metres, the difference in altitude between this bivouac and the previous one being only 500 metres. All our trekking and Andeanism programs are designed to respect this progressiveness.

Some Advice for Your Stay

In the early days

  • Especially in the first 24 hours, try to conserve energy, walk slowly and have good ventilation.
  • Not making unnecessary or thoughtless physical efforts “to test yourself”, even when you feel great (this can bring AMS)!

During a Trek or an Ascent

  • Avoid violent efforts (giant steps, jumping, running …)
  • Do not overwork yourself
  • Get a good night of sleep: Once arrived back at camp, climb 200 to 300 meters without a bag, stay there for an hour and come back down to the camp.
  • In case of symptoms (except for headaches relieved by taking aspirin), stop climbing and rest.
  • If the signs persist,  go back down from 300 to 400 meters, and only resume the progression the next day if the signs have disappeared; otherwise, you must give up continuing the trek or the ascent.

Always stay well hydrated

To avoid dehydration (favoured by the combination of altitude + sun + effort), it is essential to drink a lot (3 to 4 liters of water every day). This is also the occasion to try the famous “maté de coca” (infusion of coca leaves, a typical drink of the Andes), to give yourself some energy and to mitigate the effects of altitude.

During the treks or ascents, it will be necessary to drink mineral water or purified stream water to avoid gastrointestinal problems.

Eat Well

During the stay, and especially during a trek or an ascent:

  • Eat a balanced diet (vegetarians may be iron deficient, which slows down the production of red blood cells)
  • Have a full and abundant breakfast
  • Regularly stock up on supplies: for each day in the mountains, racing supplies (cereal bars, dried fruit, sugars) are distributed by our support teams

For your first meal at altitude, we advise you to eat light and not to consume alcohol.

Which Medication?

If you are undergoing treatment, ask your doctor for advice. They will be able to tell you if there are any contraindications to taking it at altitude, precautions to take, symptoms to watch out for, etc.

In case of headaches, prefer aspirin (which makes the blood thinner) to paracetamol.

Do not take sleeping pills, which encourage breathing breaks during sleep, and aggravate hypoxia (lack of oxygen).

The Diamox® issue

Diamox (acetazolamide) works by increasing the ventilatory response to lack of oxygen. We advise against taking it as a preventative measure. We favor natural acclimatization by a progressive rise in altitude.

It should also be noted that:

  • Diamox may cause adverse effects (metabolic disturbances)
  • Diamox is a diuretic that can cause dehydration
  • Administered preventively it makes it difficult to detect a problem related to altitude

However, it may be useful to take some with you, and we recommend that you take it:

  • In the event of poor acclimatization to altitude, especially if headaches persist despite taking pain killers
  • In case of too rapid an ascent
  • For the treatment of peripheral edema (swelling of the face, hands, ankles, significant on waking and diminishing during the day) without other signs of AMS


MAM Diagnosis

If you present symptoms of altitude sickness…Don’t tell yourself that you have a headache because you walked in the sun without a hat or that you are throwing up because the eggs from the day before were not fresh. Take a break!

The diagnosis can be vexing for a well-trained athlete, or frustrating because it involves ending a trek or climb. But ignoring it can lead to disaster!

It is essential to be honest with yourself and with the guides and chaperones who supervise the trek/climb. They have a great deal of experience in the field, and will be able to give sound advice and provide first aid if necessary. It is up to them to make the decision whether or not to let a participant continue a trek or ascent.


Staying in altitude, and particularly the practice of sports activities (trekking, mountain climbin …) in altitude is strongly contraindicated for people suffering from:

  • Vascular insufficiency
  • Chronic respiratory failure
  • Epilepsy
  • Diseases requiring repeated injections (e.g. insulin-dependent diabetes)
  • Unsettled heart disease
  • Certain blood diseases


It is also contraindicated for people who have undergone neurosurgery, or for people who have suffered from cerebral or pulmonary edema during a previous stay at altitude.

Pregnant women and infants (less than 18 months) are also not recommended to stay at high altitude.

Terra Group is committed to safety