Altitude sickness in Cusco: my personal story

It started on the second day

The first day in Cusco had been manageable. A dull headache, some unusual tiredness, nothing dramatic — I put it down to the flight and the time change and told myself the acclimatisation was going well. My travel companion was fine. We had arrived at similar times, stayed in the same hotel, eaten the same meals.

On the morning of the second day I woke with a headache that was categorically different from the one the day before. Behind my eyes and pressing outward, worsening when I moved my head quickly, made worse by the low morning light. I felt slightly nauseated. When I sat up too fast the room appeared to move briefly.

This was altitude sickness. Not the severe, hospitalisation-requiring version, but more than the mild adjustment headache that most people experience and push through. It put me in bed for most of a day that I had planned to spend at Sacsayhuaman. This is my account of what happened, what I did, and what I would do differently.

What was actually happening in my body

At 3,400 metres, Cusco’s air contains roughly 65 per cent of the oxygen density at sea level. The body responds to this reduced oxygen availability by breathing faster, producing more red blood cells over time, and increasing blood pressure to push more blood through the system. These are normal and healthy adaptations.

Altitude sickness — acute mountain sickness (AMS) in the medical terminology — occurs when the body’s adaptation is outpaced by the rate of ascent or the altitude reached. The brain and surrounding tissues can swell slightly in response to reduced oxygen. This is what causes the characteristic headache, the nausea, the disorientation.

Most cases of AMS in Cusco are mild to moderate — manageable with rest, hydration and time. Severe cases involving pulmonary oedema (fluid in the lungs) or cerebral oedema are medically serious and require immediate descent and evacuation. I did not have either of these. But I mention them because the internet can be cavalier about altitude sickness in a way that is not helpful for people travelling to Cusco for the first time.

The full altitude sickness guide covers the medical detail properly, including the warning signs that indicate serious illness and require action beyond rest and ibuprofen.

What I did (and whether it helped)

I took ibuprofen. This is standard advice and it worked — the headache reduced from a seven to a four on whatever subjective scale those numbers refer to. I lay still, which meant the nausea stayed manageable. I drank water steadily through the morning — more than felt natural, more than thirst demanded. The hotel sent up coca tea twice, which I drank without much belief in its pharmacological effect but without the energy to argue.

By early afternoon I felt well enough to sit in the courtyard. By evening I was eating a small meal. The next morning I was recovered to approximately 90 per cent — functional, manageable headache, no nausea. By the following day I felt completely normal.

What helped most, in order: rest, ibuprofen, hydration. The coca tea I am genuinely uncertain about. The coca tea guide explains the actual chemistry — the alkaloid content in a cup of mate de coca is low and the mechanism by which it might help is not fully established. It may help through mild stimulant effect on breathing; it may help because hot liquid and lying still are helpful regardless of the specific tea; it may be placebo. I drank it anyway.

What I did not do, and should have: I had not taken acetazolamide (Diamox) before arriving. Diamox is a prescription medication that reduces the risk and severity of altitude sickness by encouraging faster acclimatisation; taken 24 hours before ascent, it is well-supported by clinical evidence. I had read about it, decided I was “probably fine” and not consulted a doctor before travel. This was a poor decision. A 20-minute consultation with a travel medicine clinic before flying would have resulted in a Diamox prescription and quite possibly a full second day in Cusco rather than one spent horizontal.

What my travel companion did right

My companion had taken Diamox. She had a mild headache on day one and nothing after that. She visited Sacsayhuaman without me, reported it was extraordinary, and showed me photographs that I looked at from my bed with a mixture of admiration and regret.

She had also, before arriving, read about altitude acclimatisation seriously and followed the recommendations: no alcohol for 48 hours, light meals on arrival day, early bedtime, awareness of her breathing rate. I had read the same material and made the decision that it was probably excessive for a healthy adult. It was not excessive.

The Cusco-specific context

One thing worth understanding about Cusco is that the altitude affects people unpredictably and without clear relationship to fitness. Highly fit marathon runners sometimes experience worse AMS than sedentary office workers. Previous tolerance at lower altitudes does not guarantee tolerance at 3,400 metres. Previous good performance at Cusco does not guarantee the same on a return visit.

The acclimatisation planning guide recommends, among other things, arriving in Cusco two to three days before any strenuous activity — trekking, high-altitude day trips to Rainbow Mountain at 5,200 metres, or the Inca Trail. This buffer exists for good reason. I arrived one day before my planned Sacsayhuaman visit. That was not enough buffer.

There is also a harder point about the travel industry around Cusco. Some tour agencies are not rigorous about pre-screening participants for altitude-related conditions, and some sell trek packages to people who have not acclimatised at all. The altitude medicine scams guide addresses the other end of this — vendors near the Plaza selling overpriced “altitude remedies” of dubious value. The honest position is: real medical advice before you travel is worth more than any supplement sold at a pharmacy in the San Blas.

What I would tell someone planning their first visit

Consult a travel medicine doctor or your GP at least six weeks before your trip and discuss Diamox. It is not for everyone — there are contraindications — but the conversation is worth having. Do not self-select out of it on the assumption that altitude sickness is something that happens to other people.

Arrive in Cusco at least two days before you plan to do anything physically demanding. If you can arrive three or four days before, better still. The Sacred Valley at 2,800 metres is a lower-altitude acclimatisation option — some travellers go there before Cusco and find it significantly easier.

Do not drink alcohol for the first 48 hours. This is not cautious advice designed for fragile people — it is practical advice that will determine whether your first week in Peru is enjoyable or not.

Rest when you need to rest. The altitude is not something to prove a point about. I lost a day to stubbornness and bad preparation. The day I recovered was fine; the half-day I missed is not recoverable. These are the stakes, and they are modest enough that the precautions are entirely worth taking.

The full trip that followed — the Inca Trail, the Sacred Valley, Machu Picchu, Rainbow Mountain — was one of the best I have taken. The altitude sickness was a manageable setback that I caused by not preparing properly. That is the honest version of the story.