Updated Date:

Author: Jonas Lindqvist, 29, Sweden

Quick Summary

I flew from Lima to Cusco on a Sunday morning and was standing at the Rainbow Mountain trailhead at 6:40 a.m. on Tuesday. Less than 48 hours had passed since I arrived from sea level. I thought two nights in Cusco would be enough because that was the advice I kept seeing online. It was not enough for me.

I never reached the summit. At roughly 4,850 m, my headache, nausea and difficulty thinking clearly became serious enough that my guide stopped me and told me we were going back down. He gave me oxygen and stayed with me during the descent. The following two days then affected the rest of my Peru itinerary, including my Machu Picchu plans, train tickets, hotels and flight.

This article is an hour-by-hour account of what altitude sickness actually felt like for me. It explains the warning signs I ignored, what my guide did when things became worse, what the mistake eventually cost me and what I would change if I planned the trip again. Most importantly, it explains why fitness does not protect you from altitude illness and why I now give friends arriving directly from sea level much more time before attempting Rainbow Mountain.

The Schedule That Looked Fine on a Laptop in Stockholm

I am 29. I cycle to work year-round in Stockholm, and I had completed a four-day trek in the Julian Alps the previous summer. I was reasonably fit, so I was not worried about the physical side of Rainbow Mountain.

That confidence turned out to be part of the problem. Fitness can help with walking, but it does not prevent altitude illness.

I booked Peru in December for a February trip. I had twelve days, and the itinerary I built looked like this:

  • Saturday: Land in Lima late in the evening.
  • Sunday: Morning flight to Cusco and an afternoon to settle in.
  • Monday: Cusco city day.
  • Tuesday: Rainbow Mountain.
  • Wednesday: Train to Aguas Calientes.
  • Thursday: Machu Picchu.
  • Friday onward: Sacred Valley, more time in Cusco and a flight home the following Wednesday.

Several travel discussions I read recommended at least two nights in Cusco before Rainbow Mountain. I had two nights: Sunday and Monday.

On paper, I thought I had followed the advice.

What I had not understood was how little time that actually gave my body. I was going from Lima at sea level to Cusco at roughly 3,350 m, then to a Rainbow Mountain viewpoint above 5,000 m less than two days later.

Counting nights made the schedule sound safer than it was. Counting actual hours told a different story.

Sunday: Arrival and the False Reassurance

The flight from Lima to Cusco took about ninety minutes. Lima is at sea level, while Cusco sits at roughly 3,350 m.

I stepped out of the airport at around 10:40 a.m. and initially felt fine.

That reassured me much more than it should have.

Altitude symptoms do not necessarily appear the moment you step off the plane. According to the CDC Yellow Book, acute mountain sickness can develop after arriving at high elevation, particularly after a rapid ascent without enough time to acclimatize.

By about 2:00 p.m., I had a low, dull headache behind my forehead. I blamed the early flight.

I walked toward Plaza de Armas. The twenty-minute walk left me noticeably more out of breath than a normal twenty-minute walk should have. I stopped at a café, drank coca tea and felt somewhat better for about an hour.

Then I made my first avoidable mistake.

That evening, I met two Australians at my hostel and went out for dinner. I ordered a large plate of alpaca steak and chips and drank two large beers.

At around 9:30 p.m., I went to bed feeling heavy, bloated and headachy.

The alcohol was a particularly poor choice. The CDC recommends avoiding alcohol during the first 48 hours at high altitude because it can interfere with acclimatization and sleep. I knew I was supposed to take things easy after arriving in Cusco, but I treated that advice as optional because I felt reasonably normal.

Looking back, that was the first point where I should have taken the altitude more seriously.

Monday: The Day I Should Have Read Correctly

I woke at around 7:00 a.m. after a poor night of sleep. I had woken four or five times.

My head still hurt, and my appetite had almost disappeared. I ate about half a bread roll and left the rest.

I spent the day exploring Cusco. The idea of keeping the day easy was sensible, but I still did more walking than I should have.

I visited San Pedro Market and Qorikancha. Later, I walked uphill toward San Blas.

I stopped three times on the climb.

Instead of treating that as information, I told myself it was normal because Cusco was high.

By that evening, my headache was worse rather than better.

That is the detail I wish I had paid attention to.

A mild headache after arriving at altitude is one thing. Symptoms that continue to worsen while you remain at the same elevation deserve more caution. I was planning to climb another 1,600 m the following morning, yet my body was already telling me that I had not adjusted well to Cusco.

I went to bed at around 8:00 p.m. with an alarm set for 2:40 a.m.

I probably slept for only three and a half hours in broken fragments.

Tuesday, Hour by Hour: What It Actually Felt Like

This is the part I most wanted to document because altitude sickness is often described as a list of symptoms. My experience felt more like a sequence in which small problems gradually became impossible to ignore.

02:40 – Alarm

I woke already feeling as though I had been awake for hours. The headache was now a steady band across my forehead.

I could not face breakfast. I drank some water and put a banana in my bag. I never ate it.

03:10 – Pickup

The van collected me from my hostel. It was warm inside, which helped.

There were eleven people in the group. I took a window seat near the front and spent most of the first hour in a light, unrefreshing half-sleep.

05:25 – Breakfast Stop in Cusipata

This was the first point when somebody else noticed something was wrong.

The guide moved around the breakfast table with a pulse oximeter. When he checked me, the device showed a low oxygen saturation reading.

He asked how I had slept.

I said, “Not great.”

Then he asked whether I had a headache.

I told him it was mild.

It was not mild.

That was another mistake. I was giving my guide incomplete information because I wanted to continue with the trip.

He encouraged me to eat something even if I had little appetite. He also told me to drink water, walk slowly and stay toward the back of the group. He said he would check on me again at the trailhead.

06:35 – Trailhead at Roughly 4,630 m

Getting out of the van was the first moment when I became genuinely concerned.

The temperature was only a few degrees above freezing, and there was a light wind. When I stood up, my vision greyed slightly at the edges for a few seconds.

My heart was beating much faster than I expected while I was simply standing still.

The guide checked me again. I do not remember the exact reading. What I remember clearly was the change in his expression.

06:55 – First Fifteen Minutes of Walking

The first section of the Rainbow Mountain trail is relatively gentle. It follows a broad valley where alpacas often graze.

I could not keep pace with the group.

That was when I finally accepted that this was not simply a fitness problem. The terrain was not difficult enough to explain how bad I felt.

Other travelers passed me while I stopped repeatedly to breathe.

07:30 – Around 4,750 m

Then the nausea started.

It was not violent. Instead, it was constant and uncomfortable, similar to the feeling of being seasick.

My headache had also changed. Rather than a band across my forehead, it felt like pressure behind my eyes.

I stopped every forty or fifty metres.

By this point, the guide had dropped behind the rest of the group and was walking beside me.

08:05 – Around 4,850 m, Where I Turned Back

This was the moment that ended the hike.

I stopped walking. When I tried to start again, I briefly could not work out which direction the rest of the group had gone.

It lasted only a few seconds, but the feeling was different from normal tiredness.

I also said something out loud that did not make sense.

The guide put his hand on my shoulder and told me clearly that we were going back down.

It was not presented as a decision for me to debate.

08:05 to 09:20 – The Descent

The guide radioed the assistant guide, who remained with the rest of the group.

He then stayed with me for the descent.

He used supplemental oxygen from the tank he was carrying and stopped whenever I needed to rest. We continued downward at my pace.

By the time we were around 4,700 m, the nausea had started to ease.

When we reached the trailhead, the pressure behind my eyes had also reduced noticeably.

That experience taught me why descent matters so much in altitude illness. According to the CDC Yellow Book, descent is an essential treatment when serious altitude illness develops, while supplemental oxygen can also be important.

Coca tea was not going to solve what was happening. Neither was sitting higher on the mountain and hoping the symptoms disappeared.

09:30 to 14:00 – Waiting

I sat in the van wrapped in a blanket while the rest of the group completed the hike.

I gradually felt better.

I also felt embarrassed.

In hindsight, the embarrassment was unnecessary. Turning around was exactly what needed to happen. The dangerous decision would have been pretending I was fine so that I could reach the viewpoint.

The Guide’s Reaction Was Not What I Expected

I had expected him to be irritated.

I had slowed the group, required one guide to separate from the others and used some of the oxygen supply.

Instead, he was calm and matter-of-fact.

Afterward, he asked what day of the trip I was on.

I told him it was Day 3 and only my second full day in Cusco.

He immediately understood the pattern.

He explained that he regularly sees travelers fly directly into Cusco from much lower elevations, feel reasonably normal on their first day and then attempt Rainbow Mountain before their bodies have had enough time to adjust.

One part of that conversation stayed with me.

Being physically fit had made me confident that I could push through discomfort. However, cardiovascular fitness does not make somebody immune to acute mountain sickness. What matters much more is the rate of ascent, previous acclimatization and individual susceptibility.

I had treated my headache like the discomfort from a hard workout.

It was not the same thing.

If you want to see current traveler feedback about guide support and oxygen, the real Rainbow Mountain Travels Tripadvisor listing includes recent reviews describing guides assisting travelers who struggle with the altitude.

What the Mistake Cost Me in Actual Money

This is the part I rarely saw discussed while planning my trip.

Altitude problems do not only affect the mountain day itself. They can disrupt everything booked immediately afterward.

I returned to Cusco at around 3:30 p.m. on Tuesday. I was functional, but I felt completely drained.

Wednesday was supposed to be my train journey to Aguas Calientes. Thursday was supposed to be Machu Picchu.

On Wednesday morning, I still had a headache. My appetite had not fully returned, and I had slept poorly again.

I decided not to continue immediately with the Machu Picchu portion of the trip.

That decision created a chain of extra costs:

  • Machu Picchu entry ticket: about $52 USD that I could not recover.
  • Round-trip train tickets between Ollantaytambo and Aguas Calientes: about $130 USD. I recovered roughly $40 through the change arrangement, leaving approximately $90 in losses.
  • Aguas Calientes hotel: about $48 USD for a non-refundable night.
  • Three additional nights in Cusco: about $105 USD while I recovered and reorganized the itinerary.
  • New Machu Picchu entry and replacement train arrangements: about $180 USD.
  • Cusco-to-Lima flight change: about $165 USD.

My total additional cost was roughly $640 USD.

That number is specific to my bookings. Another traveler could lose much less or much more depending on refund rules, ticket types and hotel policies.

However, it changed how I think about acclimatization days.

Two extra hostel nights might have cost me around $70. Instead, I built an itinerary with almost no flexibility and eventually spent several hundred dollars changing it.

I also never reached the Rainbow Mountain viewpoint.

That is the part that does not appear on a receipt.

What I Would Do Differently: Five Specific Changes

1. I Would Give Myself More Time Before Rainbow Mountain

The biggest planning mistake was treating “two nights” as a precise medical rule.

It is not.

I arrived in Cusco late Sunday morning and left for Rainbow Mountain at about 3:00 a.m. on Tuesday. That gave me roughly forty hours at Cusco’s elevation before climbing much higher.

It also included poor sleep, a night of alcohol and more physical activity than I needed.

The CDC Yellow Book recommends gradual ascent and suggests spending additional time acclimatizing rather than moving rapidly from low elevations to much higher sleeping or activity elevations.

If I planned the same trip again, I would personally place Rainbow Mountain on Day 4 or later after flying directly from sea level to Cusco.

That is my planning rule based on what happened to me. It is not a guarantee that Day 4 is safe for every traveler. Some people need more time, and symptoms should always matter more than the calendar.

2. I Would Discuss Acetazolamide Before Traveling

I did not take acetazolamide before my trip.

If I were planning another rapid ascent, I would discuss it with a doctor or travel medicine specialist before leaving home.

Acetazolamide, commonly known by the brand name Diamox, can accelerate acclimatization and reduce the risk of acute mountain sickness for some travelers.

The current CDC Yellow Book lists a common adult preventive dose of 125 mg every 12 hours. Preventive use normally begins the day before ascent and continues during the initial period at altitude.

However, it is still medication. The right dose and whether it is appropriate depend on the traveler.

One correction is important here. Acetazolamide is a sulfonamide derivative, but that does not mean everybody with an allergy to sulfonamide antibiotics automatically cannot take it. The CDC notes that cross-sensitivity between sulfonamide antibiotics and acetazolamide has not been reported. People with a history of serious drug reactions should still discuss their situation with a clinician.

I would make that decision before the trip rather than trying to diagnose and medicate myself after arriving in Cusco.

3. I Would Avoid Alcohol During the First 48 Hours

The two beers on Sunday night were one of the easiest mistakes to avoid.

The CDC specifically recommends avoiding alcohol during the first 48 hours at high altitude.

That does not mean the beers caused everything that happened to me. My rapid ascent from sea level was the much bigger issue.

However, drinking on my first night was certainly not helping my sleep or acclimatization.

If I returned to Cusco directly from sea level, I would keep the first two days alcohol-free.

4. I Would Eat Simply and Keep the First Day Easy

I would also make the first day boring on purpose.

I would eat a lighter dinner, drink enough water and avoid turning arrival day into a sightseeing marathon.

There is no need to invent a complicated theory about heavy food causing altitude illness. My real problem was rapid ascent.

However, eating a huge dinner while I already felt headachy and slightly unwell made an uncomfortable evening even less comfortable.

Soup, bread, fruit and an early night would have suited me much better.

The alpaca steak could have waited.

5. I Would Treat Worsening Symptoms as Information

This is the most important change.

My symptoms were getting worse on Monday evening, yet I still set a 2:40 a.m. alarm to climb higher.

The CDC advises travelers with altitude illness not to continue ascending while symptoms are present. More serious neurological symptoms or severe breathing problems require urgent attention and descent.

I already had a worsening headache, loss of appetite and poor sleep before the van even arrived.

That should have changed my plan.

I ignored those signals because the tour was booked, the alarm was set and I wanted the photograph.

No prepaid tour is important enough to make worsening symptoms irrelevant.

The Alternative Route I Wish I Had Considered

Another way I could have approached the trip was to avoid flying directly from sea level to Cusco at the beginning.

Traveling overland through southern Peru creates a more gradual elevation profile.

For example, the route with Peru Hop can connect Lima with Paracas, Huacachina, Arequipa, Puno and Cusco.

The elevations rise in stages rather than jumping directly from Lima to Cusco in one flight. Lima and Paracas are close to sea level, Huacachina remains low, Arequipa sits at roughly 2,300 m and Puno is above 3,800 m before the route reaches Cusco.

That does not guarantee that a traveler will avoid altitude sickness. Individual responses vary enormously. However, gradual ascent is consistent with the general acclimatization principle recommended by altitude-medicine guidance.

The route also turns the travel days into part of the trip rather than treating them only as transportation.

Stops can include coastal scenery in the Paracas National Reserve, Huacachina, Arequipa and Lake Titicaca before reaching Cusco.

In my case, flying saved several days on paper. The irony is that I later lost days reorganizing my itinerary after Rainbow Mountain.

Public buses can still make sense for travelers who speak Spanish comfortably and want direct transportation from one city to another. However, they require more logistics.

Lima does not have one single central terminal used by every intercity company. Travelers may need to reach a company-specific depot, arrive early enough for check-in and organize another transfer at the destination.

For a multi-stop route, I would compare the full cost and convenience rather than looking only at the bus ticket.

The current Peru Hop Tripadvisor listing has thousands of recent traveler reviews discussing hotel pickups, onboard hosts, flexibility and the overland route through Peru.

The Rule I Now Give Friends Arriving From Sea Level

I have repeated this to several friends since returning home.

If I were flying directly from sea level to Cusco again, I personally would not put Rainbow Mountain at the beginning of the itinerary.

My own rule would be Day 4 or later, counting arrival as Day 1.

Again, this is a planning buffer based on my experience, not a medical guarantee.

The calendar never overrides symptoms. If I still had a worsening headache, nausea, unusual fatigue or other concerning symptoms on Day 4, I would postpone the hike.

If the trip were too short to allow enough time, I would consider one of three options:

  • Travel overland through intermediate elevations so acclimatization begins during the journey.
  • Build several easier days into the Cusco region before attempting Rainbow Mountain.
  • Skip Rainbow Mountain on that trip rather than forcing it into an itinerary that does not have enough flexibility.

Rainbow Mountain will still be there on another trip.

The mistake I made was treating my twelve-day itinerary as fixed while expecting my body to adapt to it.

Key Numbers and Guidance

  • Cusco: approximately 3,350 m above sea level.
  • Rainbow Mountain trailhead: roughly 4,630 m above sea level.
  • Main Rainbow Mountain viewpoint: approximately 5,036 m above sea level.
  • CDC acclimatization guidance: avoid going directly from low elevation to a sleeping altitude above roughly 2,750 m in one day when possible.
  • Initial activity: the CDC recommends only mild exercise during the first 48 hours at altitude.
  • Alcohol: the CDC recommends avoiding alcohol for the first 48 hours at high altitude.
  • Acetazolamide prevention: the CDC lists 125 mg every 12 hours as a common adult preventive dose, generally beginning the day before ascent. Travelers should discuss medication with a healthcare professional.
  • Important rule: do not continue ascending when altitude symptoms are worsening.
  • Rainbow Mountain Travels: the current Tripadvisor listing describes first aid, oxygen tanks and bilingual guides as part of the operator’s equipment and service.

FAQ

Are Two Nights in Cusco Enough Before Rainbow Mountain?

There is no number of nights that guarantees a traveler will be properly acclimatized. In my case, two nights gave me only about forty hours in Cusco before a 3:00 a.m. departure for Rainbow Mountain, and I was already showing worsening symptoms before the tour. Current CDC guidance focuses on gradual ascent rather than a fixed number of nights. After my experience, I would personally schedule Rainbow Mountain on Day 4 or later when flying directly from sea level, but I would postpone it again if symptoms were still present.

What Were the First Warning Signs I Should Have Taken Seriously?

For me, the pattern was more important than any single symptom. I slept badly on the first night, lost my appetite the following morning and still had a headache. Most importantly, the headache was worse on Monday evening than it had been on Sunday. I was not improving at the same elevation, yet I planned to climb another 1,600 m the following morning. That was the point when I should have changed the itinerary and asked for medical advice rather than treating the symptoms as something to push through.

Should I Take Diamox Before Rainbow Mountain?

Acetazolamide, commonly known by the brand name Diamox, can help speed acclimatization and reduce the risk of acute mountain sickness for some travelers. The CDC lists 125 mg every 12 hours as a common adult preventive dose and recommends beginning preventive use the day before ascent. However, medication decisions should be made with a doctor or travel medicine professional, especially if you have medical conditions, take other medicines or have a history of serious drug reactions. Acetazolamide can support acclimatization, but it does not replace gradual ascent or justify ignoring symptoms.

What Should I Do if I Start Feeling Bad at the Trailhead?

Tell your guide exactly how you feel. Do not minimize a headache, nausea, dizziness, unusual weakness or changes in thinking because you are afraid of missing the viewpoint. That is what I did at breakfast, and it made it harder for my guide to understand my condition immediately. A responsible guide can slow the pace, monitor you, stop the hike or begin descending if necessary. Serious or worsening altitude symptoms should be treated seriously, and descent may be required.

Does Coca Tea Prevent Altitude Sickness?

I would not rely on it. Coca tea is a traditional drink in the Andes, and I found a warm cup comforting when I first arrived in Cusco. However, it did not fix my underlying problem, which was ascending too quickly. Current medical guidance focuses on gradual acclimatization, appropriate pacing and medical prevention when indicated. Coca tea should not be treated as a substitute for those measures.

Does Being Fit Protect You From Altitude Sickness?

No. This was one of my biggest misconceptions. I cycled regularly and had previous hiking experience, but neither prevented me from becoming sick. Physical fitness can make the walking itself easier, but susceptibility to acute mountain sickness is not determined by how athletic you are. The speed of ascent, acclimatization and individual response matter much more.

Is Palccoyo an Easier Alternative to Vinicunca?

Palccoyo is often considered a gentler walking experience because the route is generally shorter and less steep than the classic Vinicunca hike. However, it is still a genuinely high-altitude destination. I would not use Palccoyo as a way to bypass acclimatization problems. If I were already experiencing altitude symptoms in Cusco, I would postpone high-altitude excursions rather than assuming a shorter trail automatically makes them appropriate.

Should I Go to Rainbow Mountain if I Still Have a Headache in Cusco?

I would not make that decision based only on a tour reservation. A headache can have many causes, but a persistent or worsening headache after a rapid ascent to Cusco deserves attention before climbing to more than 5,000 m. Current CDC guidance says travelers with acute altitude illness should avoid further ascent until symptoms have resolved. If symptoms are severe, unusual or worsening, seek medical advice rather than trying to diagnose the problem yourself.

Limitations

This article describes one traveler’s experience in 2026. People respond very differently to altitude. One person may feel fine after a rapid arrival in Cusco while another may develop symptoms despite taking more time. My experience should not be used to predict exactly how another traveler will respond.

The costs also reflect my own February 2026 bookings, ticket conditions and exchange rates. Machu Picchu tickets, trains, hotels, flights and cancellation policies can change. Another traveler may be able to recover more money or may lose considerably more.

The medical information in this article is intended to explain the lessons I took from the experience, not to replace individual medical advice. Travelers with medical conditions, previous severe altitude illness or questions about acetazolamide should speak with a doctor or travel medicine specialist before traveling.

For current Rainbow Mountain tour details, guide support and availability, contact Rainbow Mountain Travels directly. If you need to change a tour because you are not feeling well, contacting the operator early is much better than forcing yourself onto a departure simply because it has already been paid for.