Altitude Sickness in Cusco: Symptoms, What to Do on Day One and When to Get Help

Cusco sits at roughly 3,400 meters above sea level. Many travelers arrive by plane from Lima, which is close to sea level, so the body has no time to adjust. This guide summarizes what medical and institutional sources say about altitude sickness (also called soroche or acute mountain sickness), how to plan your first day and when not to wait it out. It is not medical advice: if you have questions about your health, talk to a professional before you travel.

Altitudes to keep in mind

• Cusco: Wikipedia gives 3,399 m and says “around 3,400 m.” The US CDC cites about 3,350 m.
• Ollantaytambo (Sacred Valley): 2,792 m, according to Wikipedia.
• Machu Picchu (the citadel): 2,430 m, according to Wikipedia.

By those figures, Ollantaytambo is about 600 m lower than Cusco. The CDC sorts risk by the altitude where you sleep: low below 2,750 m, medium between 2,750 and 3,400 m, and high above 3,400 m. Cusco sits right at the boundary between the last two levels.

What it is and when it shows up

According to the CDC (Yellow Book), unacclimatized travelers sleeping at 2,450 m or higher, and sometimes lower, are at risk of acute mountain sickness. Symptoms usually start 2 to 12 hours after arrival, often during the first night, and if you don’t go higher they usually resolve within 12 to 48 hours.

The main symptom is a headache, together with at least one of these: loss of appetite, dizziness, fatigue, nausea or, sometimes, vomiting. The CDC compares it to a hangover. Children are as susceptible as adults.

How to plan your first day

These ideas come from the CDC and Peru’s Ministry of Health (Minsa):

• Ascend gradually. The CDC notes that travelers arriving in Cusco or La Paz can sleep one or two nights at a lower elevation than the airport before going up, which may make medication unnecessary. For reference, Ollantaytambo, in the Sacred Valley, is about 600 m lower than Cusco.
• Light activity and no alcohol for the first 48 hours. This is the CDC’s recommendation.
• Eat light and stay hydrated. According to Minsa, quoted by Radio Nacional (July 29, 2026), the best approach is light meals, avoiding excess and eating small portions several times a day during the first 24 hours in the highlands.
• Don’t force fluids. The Wilderness Medical Society guideline (summarized in American Family Physician, 2020) says drinking excessively doesn’t prevent altitude illness and raises the risk of hyponatremia. Avoiding dehydration still matters, because it can resemble altitude sickness.
• Keep your usual caffeine if you use it: the CDC warns that stopping suddenly can cause a headache.
• Don’t sleep higher with symptoms. The CDC is clear: don’t ascend to sleep at a higher altitude if you have symptoms of altitude illness, however minor they seem.

What doesn’t help much

The Wilderness Medical Society guideline (2019, summarized in American Family Physician) says oxygen canisters, oxygen bars and powdered drink mixes are not expected to help. It also lists coca products among the things not recommended for preventing altitude sickness. This is not a comment on their cultural use, only what that guideline says about prevention.

Medication: talk to a doctor before you travel

The CDC and the Wilderness Medical Society mention acetazolamide as a drug that helps speed acclimatization, and that is considered more strongly for travelers at moderate to high risk. It has contraindications, and the guideline recommends planning its use ahead of time. Ask your doctor before the trip whether it suits you and how to use it.

Minsa stresses not self-medicating. According to Minsa, drugs against soroche should be used only with a professional’s backing, and in children never without an evaluation.

Who should be more careful

Minsa lists small children, older adults, pregnant women and people with heart or lung conditions as the most vulnerable groups. On pregnancy, the CDC says there are no studies or case reports of fetal harm from brief high-altitude travel, and that some clinicians may advise against sleeping above 3,050 m. If you are in any of these groups, check with a doctor before traveling.

Warning signs: when to descend and seek medical care

Mild altitude sickness improves with rest and without going higher. But some signs should not be waited out. According to the CDC and Minsa:

• Getting worse despite rest or treatment: the CDC says to descend.
• Confusion, unsteady walking (loss of balance) or excessive drowsiness: may signal high-altitude cerebral edema. The CDC calls for urgent care.
• Shortness of breath at rest, persistent cough, chest tightness or bloody sputum: may signal high-altitude pulmonary edema. The CDC calls for urgent care and descent.
• Severe, persistent headache, vomiting or loss of consciousness: Minsa lists these among the reasons to go to emergency services.
• In children: being very listless, refusing fluids or having trouble breathing, according to Minsa.

The most important treatment is going down. The Wilderness Medical Society recommends descending 300 to 1,000 m until symptoms resolve, and the CDC says altitude sickness improves quickly with a descent of at least 300 m. In practice, if you have serious symptoms in Cusco, tell your lodging or a medical service so they can advise you on how to descend and where to be seen.

In short

• Cusco is at about 3,400 m; the Sacred Valley is lower (Ollantaytambo, 2,792 m).
• Symptoms usually appear 2 to 12 hours after arrival and improve within 12 to 48 hours if you don’t go higher.
• First 48 hours: light activity, no alcohol, light meals and good hydration without overdoing it.
• Don’t medicate on your own; if you want to consider acetazolamide, talk to your doctor before the trip.
• Confusion, shortness of breath at rest, severe headache or worsening symptoms: descend and get medical care.