Altitude in the Andes: A Plain-English Acclimatisation Guide
Altitude illness is caused by low oxygen pressure, not by a lack of fitness. A traveller who runs every day can still become ill after flying directly to Cusco or La Paz. The most useful planning tools are time, a gradual rise in sleeping altitude, and a willingness to stop ascending when symptoms worsen.
What the numbers mean
| Place | Approximate elevation | Planning implication |
|---|---|---|
| Cusco | 3,350 m | A direct flight puts an unacclimatised traveller at a high sleeping altitude. |
| La Paz | 3,650 m | Consider a staged arrival or lower first sleeping base where practical. |
| Lake Titicaca | 3,810 m | Do not assume a lakeside day is a low-altitude recovery day. |
| High passes and refuges | Often above 4,000 m | Sleeping-height gain and symptoms matter more than the day’s highest photo stop. |
A conservative acclimatisation pattern
- Ascend gradually where the route allows.
- Keep exercise mild during the first 48 hours at a new high altitude.
- Once above 3,000 metres, avoid increasing sleeping altitude by more than about 500 metres per day and add an acclimatisation night for each additional 1,000 metres gained.
- Avoid alcohol for the first 48 hours at altitude.
- Do not continue higher with worsening symptoms.
These are general recommendations from the CDC Yellow Book; individual susceptibility varies. Day trips to a higher point followed by sleep lower are generally less stressful than sleeping at the day’s maximum altitude.
Common early symptoms
Headache after gaining altitude, together with tiredness, dizziness, nausea, or poor sleep, can fit acute mountain sickness. Dehydration, migraine, infection, alcohol, and exhaustion can look similar, so do not self-diagnose a serious or worsening condition from a checklist.
Warning signs that need urgent action
Confusion, loss of coordination, severe breathlessness at rest, cough with chest symptoms, or rapid deterioration can signal a life-threatening emergency. Stop ascending, seek medical help, and descend promptly when serious altitude illness is suspected. Do not rely on a tour itinerary or a single oxygen reading to overrule symptoms.
Medication is a clinician conversation
Acetazolamide can speed acclimatisation and may be considered when abrupt ascent is unavoidable, but it is not a substitute for a sensible itinerary. Dosing, contraindications, and emergency medicines should be discussed with a qualified clinician who knows your medical history.
This page is educational travel information and does not provide diagnosis or individual medical advice.
Primary source
Read the current CDC Yellow Book chapter on high-altitude travel and altitude illness before finalising a high-elevation itinerary.