At what altitude does altitude sickness start?

Most people don't experience symptoms below 8,000 feet. Mild symptoms can start between 8,000-10,000 feet. Above 12,000 feet, most unacclimatized people will experience some symptoms.

How long does it take to acclimatize?

Initial acclimatization takes 1-3 days at each new altitude level. Full acclimatization to very high altitudes (above 14,000 feet) can take 2-3 weeks. Your body continues adapting for months.

Does physical fitness prevent altitude sickness?

No. Altitude sickness affects people regardless of fitness level. In fact, very fit people sometimes push too hard too fast and make symptoms worse. Age, gender, and previous altitude experience are better predictors.

Is coca tea actually helpful?

Yes, coca leaves contain mild alkaloids that can help with altitude symptoms. The effect is subtle but real. Coca tea is legal and widely available in Peru, Bolivia, and northern Argentina.

What if I get sick on a multi-day trek?

Tell your guide immediately. Good operators will have evacuation plans and oxygen. If symptoms are severe, you'll need to abandon the trek and descend. Don't risk it—guides have seen altitude sickness before and take it seriously.

How to Handle Altitude Sickness in the Andes

Ascend gradually (no more than 1,000 feet per day above 8,000 feet), stay hydrated, avoid alcohol, and recognize symptoms early. Most cases resolve with rest and descent if needed. Severe symptoms require immediate descent and medical attention.

Prepare before you go. Start drinking extra water 2-3 days before arrival. Consider arriving in a gateway city like Cusco (11,200 feet) or La Paz (12,000 feet) and spending 2-3 days there before going higher. Ask your doctor about acetazolamide (Diamox) if you're going above 9,000 feet.
Ascend slowly. Follow the golden rule: climb high, sleep low. Don't gain more than 1,000 feet of sleeping elevation per day above 8,000 feet. If driving or flying directly to high altitude, plan rest days. From Cusco to Machu Picchu (7,970 feet) is actually descending, but Sacred Valley towns like Ollantaytambo (9,160 feet) are good middle grounds.
Stay hydrated and eat right. Drink 3-4 liters of water daily at altitude. Eat carbohydrate-rich foods (quinoa, potatoes, rice) which require less oxygen to metabolize. Avoid alcohol for the first 48 hours—it worsens dehydration and can mask altitude sickness symptoms.
Recognize the symptoms. Mild symptoms (headache, nausea, fatigue, dizziness) are normal and usually improve in 1-2 days. Warning signs requiring descent: severe headache that doesn't respond to painkillers, vomiting, confusion, difficulty walking, or fluid in lungs (crackling breath sounds).
Treat mild symptoms. Rest and avoid further ascent until symptoms improve. Take ibuprofen or acetaminophen for headaches. Drink coca tea (legal and helpful in South America). Light exercise like walking can help, but avoid strenuous activity.
Know when to descend. If symptoms worsen after 24 hours or you develop severe symptoms, descend immediately to the last elevation where you felt well. Even 1,000-2,000 feet can make a huge difference. This is not optional—altitude sickness can be fatal.

At what altitude does altitude sickness start?: Most people don't experience symptoms below 8,000 feet. Mild symptoms can start between 8,000-10,000 feet. Above 12,000 feet, most unacclimatized people will experience some symptoms.
How long does it take to acclimatize?: Initial acclimatization takes 1-3 days at each new altitude level. Full acclimatization to very high altitudes (above 14,000 feet) can take 2-3 weeks. Your body continues adapting for months.
Does physical fitness prevent altitude sickness?: No. Altitude sickness affects people regardless of fitness level. In fact, very fit people sometimes push too hard too fast and make symptoms worse. Age, gender, and previous altitude experience are better predictors.
Is coca tea actually helpful?: Yes, coca leaves contain mild alkaloids that can help with altitude symptoms. The effect is subtle but real. Coca tea is legal and widely available in Peru, Bolivia, and northern Argentina.
What if I get sick on a multi-day trek?: Tell your guide immediately. Good operators will have evacuation plans and oxygen. If symptoms are severe, you'll need to abandon the trek and descend. Don't risk it—guides have seen altitude sickness before and take it seriously.