Altitude Sickness in Cusco: How to Acclimatize Before Your Trek
Cusco sits at 3,400 m (11,150 ft), and most people fly in from sea level in little over an hour. The air here has about a third less oxygen in every breath, so a mild headache, poor sleep and being out of breath on stairs in the first 24 to 48 hours are normal and affect most visitors. Serious altitude illness is rare in Cusco itself and almost always comes from going higher too fast. The plan below is what we send every client: arrive two or three days before your trek, take it easy on day one, and know the few symptoms that mean you should talk to a doctor.
Why Cusco hits you on the first day
Altitude sickness is not about fitness. Marathon runners get it and grandmothers do not, because it depends on how fast you gain altitude and on your individual physiology, not on your training. The usual trigger in Peru is the flight: Lima is at sea level, Cusco at 3,400 m (11,150 ft), and the plane takes 75 minutes.
Symptoms of acute mountain sickness typically appear 6 to 12 hours after arrival, which is why you can feel fine at the airport and bad at dinner. They usually peak on the first night and improve by the second or third day as your body produces more red blood cells and breathes faster to compensate.
Machu Picchu is lower than Cusco, at 2,430 m (7,970 ft), so if your trip is Cusco first and Machu Picchu after, the hardest day for altitude is your first one.
The altitudes you will visit
| Place | Altitude | What it means |
|---|---|---|
| Lima | Sea level | Where most people fly in from |
| Machu Picchu | 2,430 m (7,970 ft) | Lower than Cusco; a relief for most |
| Ollantaytambo, Sacred Valley | 2,800 m (9,186 ft) | The best place to sleep the first nights |
| Cusco | 3,400 m (11,150 ft) | Where you acclimatize |
| Humantay Lake | 4,200 m (13,780 ft) | A day hike; go on day 3 or later |
| Dead Woman's Pass, Inca Trail | 4,215 m (13,828 ft) | Highest point of the Inca Trail, Day 2 |
| Salkantay Pass | 4,600 m (15,090 ft) | Highest point of the Salkantay Trek, Day 2 |
| Rainbow Mountain (Vinicunca) | 5,036 m (16,522 ft) | Only after several days of acclimatization |
Symptoms: what is normal and when to worry
- Normal in the first two days: headache, tiredness, loss of appetite, mild nausea, trouble sleeping, waking up breathless, needing to stop on stairs. This is acute mountain sickness (AMS) and it passes with rest, fluids and time.
- Talk to a doctor if: the headache does not respond to ibuprofen or paracetamol, you vomit repeatedly, or symptoms get worse after the second day instead of better.
- Emergency, descend and seek help immediately: confusion, stumbling or being unable to walk in a straight line, severe breathlessness at rest, a wet cough or frothy sputum, blue lips. These are signs of fluid on the brain or lungs (HACE or HAPE). They are very rare in Cusco but they are the reason we never push a client who is unwell to go higher.
- Do not go higher with symptoms. The rule is simple: you can stay at the altitude where symptoms started, but you do not climb until they are gone.
A three-day acclimatization plan that works
Day 1, arrival. Go to your hotel and rest for a few hours. Eat light, drink water steadily, no alcohol, and no sightseeing that involves hills. A short walk to the Plaza de Armas in the late afternoon is fine; climbing to San Blas or Sacsayhuamán is not. If you have the choice, sleep in the Sacred Valley at Ollantaytambo or Urubamba (2,800 to 2,900 m), 600 m lower than Cusco, and come up to the city the next day.
Day 2. A walking tour of Cusco at a slow pace, or the Sacred Valley by vehicle: Pisac, Ollantaytambo and Chinchero. You are moving, which helps, but not pushing. Early night.
Day 3. A proper day hike if you feel good: Humantay Lake at 4,200 m is the classic test before a trek. If you feel fine at the lake, you are ready for the Salkantay Pass or Dead Woman's Pass.
Day 4. Your trek starts. Our Classic Inca Trail and Salkantay Trek itineraries are built so that you always sleep lower than the highest point you reached that day, which is the most effective single protection against altitude illness. That is why we do not take clients straight from the airport to a trek, whatever the dates.
Coca tea, Diamox and what actually helps
Going slowly and sleeping low are the two things that work best, and they are free. Everything else is secondary.
Acetazolamide (Diamox) is the only medication proven to prevent acute mountain sickness. The usual preventive dose is 125 mg twice a day, starting the day before you go up and continuing for two days at altitude. It needs a prescription in most countries, has side effects (tingling fingers, frequent urination, flat-tasting fizzy drinks) and is not for people allergic to sulfa drugs, so ask your doctor before you travel. Pharmacies in Cusco sell it, but your doctor at home knows your history.
Ibuprofen or paracetamol treat the headache. Coca tea and coca leaves are a mild stimulant that many people find helps with tiredness and appetite; they are legal in Peru and offered in every hotel lobby. They do not prevent altitude sickness, but they do not hurt either. Oxygen is useful for relief, not prevention; many hotels have it and we carry emergency oxygen on the Inca Trail.
What does not help: alcohol on the first two days, sleeping pills (they slow your breathing at night, exactly when you need it faster), and heavy meals the first evening.
What we do about altitude on our treks
Our guides are trained in first aid and see altitude symptoms every week of the season, so they recognise early signs long before clients mention them. Pace is set by the slowest walker, water and snack stops are scheduled, and every itinerary sleeps lower than its highest point.
On the Inca Trail we carry emergency oxygen and a first aid kit, and there is a plan for every section of the route. On Salkantay the road access at Soraypampa and Chaullay means a client who is unwell on Day 1 or 2 can be driven down, which is one reason we recommend Salkantay to travellers who worry about altitude.
If you have a heart or lung condition, are pregnant, or have had altitude illness before, tell us when you book and talk to your doctor. With a sensible plan, almost everyone who comes to Cusco enjoys the trek they came for.
Frequently asked questions
How many days do I need in Cusco before the Inca Trail?
Two full days minimum, three if you can. Arrive, rest, do a gentle day, then a day hike such as Humantay Lake. If you only have one day, sleep in the Sacred Valley rather than Cusco and keep the day very easy.
Is Machu Picchu higher than Cusco?
No. Machu Picchu is at 2,430 m, almost 1,000 m lower than Cusco at 3,400 m. Most people feel noticeably better there.
Should I take Diamox for Cusco?
It is a decision for you and your doctor. Many travellers acclimatize well with two easy days and no medication. If you have had altitude sickness before, have a tight schedule or are going straight to a high trek, acetazolamide is the proven option. Start it the day before you fly up.
Does coca tea prevent altitude sickness?
No. It can ease tiredness and nausea and it is part of the experience, but it has no proven preventive effect. Going slowly and sleeping low do.
Can children get altitude sickness in Cusco?
Yes, at the same rate as adults, and they may not describe the symptoms well. Watch for unusual tiredness, fussiness, loss of appetite or vomiting, keep the first day very quiet and ask your paediatrician before the trip.
What if I get sick during the trek?
Tell your guide at once. On Salkantay you can be driven down from the first two camps. On the Inca Trail the guide stays with you, slows the pace and uses the emergency oxygen if needed; after Day 1 the only way out is forward or back on foot, which is why we insist on acclimatizing first.
Official sources: CDC Yellow Book: High Altitude Travel and Altitude Illness · UNESCO World Heritage: City of Cuzco
