As a pilot, I am familiar with the Federal Aviation Regulation that requires pilots to use supplemental oxygen when flying above 12,500 feet for more than 30 minutes without pressurization.

I also remember a ski trip to Breckenridge, Colorado, several years ago that saw my husband suffering headaches and mild nausea as a result of trying to exert ourselves at 9,600 feet, though the overall elevation change had been less than 4,400 from where our trip had originated: the mile-high city of Denver.

In November I traveled with a friend to her home country of Peru. We spent the first week in Lima, which sits comfortably near sea level, enjoying the city and beaches and delicious meals at exclusive clubs offering sweeping views of the Pacific.

And then we flew to Cusco, the jet expertly skimming the top of the rugged Andes Mountains before dropping us into the former capital city of the Inca Empire.

Aware that we were about to experience an extreme change in altitude — essentially going from sea level in Lima to 11,152 feet in Cusco — my friend and I began preparing 48 hours in advance by taking Acetazolamide pills to prevent and reduce the symptoms of altitude sickness.

Nonetheless, the change was palpable the minute I set foot in Cusco’s Alejandro Velasco Astete International Airport. Though subtle, I immediately noticed a slight dizziness; even my eyesight seemed a little blurry, as if I was moving through a dense haze or fog. The feeling was like waking from a deep dream or a long nap on a hot beach — slightly woozy and disoriented.

Was I simply hyper-aware? Or, if I hadn’t known I was now existing at an altitude near which pilots should be using supplemental oxygen, would I simply have attributed the sensations to normal travel fatigue?

As recommended, my friend and I took it easy on the first day, resting in our rented apartment, drinking lots of water, eating light meals and, probably most importantly, sipping mate de coca — an herbal tea made using the raw dried leaves of the native South American coca plant, the leaves of which provide the raw material for cocaine.

According to culturelocker.com, “Chewing the leaves or drinking coca tea when you’re in Cusco clears your throbbing head and lets you breathe again.”

And it’s perfectly legal. So drink we did — as often as possible or necessary — and I was glad for it. As a former migraine sufferer and someone whose head is sensitive to pressure changes in the best of circumstances, I dreaded the thought that my much-anticipated adventures in Cusco would be sabotaged by debilitating headaches. Or worse.

Altitude sickness is no joke, with symptoms — including headache, nausea, vomiting, shortness of breath, loss of appetite, fatigue, and rapid heart rate — typically occurring within hours of arrival. In extreme cases, altitude sickness can lead to death.

According to the Mayo Clinic, mild cases of altitude sickness may self-resolve in one to three days, while more severe cases require oxygen, medication and moving to a lower altitude. Indeed, we encountered several tourists who recounted tales of friends and fellow travelers who’d had to return immediately to Lima due to experiencing adverse effects of the altitude.

Columnist’s note: This column is the first in a two-part series on acclimating to high altitudes.