How to acclimatize to high altitude

Learn how to adjust to high altitude without getting sick:

Ascending too quickly above 10,000 feet elevation can cause nausea, headaches, or sleeplessness due to acute mountain sickness (AMS, altitude sickness, or soroche in Spanish).

For most people, the best way to acclimatize above 10,000 feet elevation is to “climb high and sleep low.” In other words, day hike to higher elevations, but sleep no more than 2000 feet (600 meters) higher each day. Take time to naturally adjust to higher altitudes without relying on a drug with side affects such as Diamox — compare with the safer Ginkgo Biloba herb below. How fast you acclimatize is unpredictable and can vary for the same person on different occasions. Descending quickly towards sea level is the best cure if you become altitude sick.

Ginkgo Biloba versus Diamox

If tight trip schedules restrict time available for safe acclimatization, try the natural herb Ginkgo Biloba (available over the counter without a prescription), which has fewer undesirable side effects than Diamox (Acetazolamide), the drug most commonly prescribed by doctors for preventing altitude sickness. Common side effects of Diamox include frequent urination (risks dehydration), numbness and tingling in fingers and toes, taste alterations, blurred vision, and risk of kidney stones. Ginkgo Biloba has far fewer side effects (though it may not prove as effective as Diamox, and pregnant women and people taking antidepressants should first consult their doctor). Don’t take Ginkgo Biloba and Diamox together, as they nuetralize each other’s effect.

Directions: Take 100 to 120 milligrams of Ginkgo Biloba herb twice a day starting 3-5 days before ascending, and continue for 2-3 days at maximum sleeping altitude. In the year 2000, a Ginkgo Biloba clinical study on Pike’s Peak with 40 college students reduced altitude sickness by 50% compared to the placebo group.

Starting at sea level, my sleep was significantly better in my first 2 nights in Cuzco (at 11,000 feet) when taking Ginkgo Biloba herb in 2003, compared to my trip in year 2000 without the herb. On our high altitude Huayhuash Trek in the Andes of Peru, most of our group of 11 men took 120 milligrams of Ginkgo Biloba herb twice a day starting 5 days before ascending, and no one experienced serious problems from mountain sickness. In Nepal, we extended acclimatization time by first trekking Annapurna Sanctuary before the higher Gokyo Valley (Mount Everest area) and felt no significant altitude problems.

Coca leaf tea (mate de coca) in South America

In South America, your risk of feeling nausea due to altitude may also be reduced by drinking local coca leaf tea (mate de coca), the mild, traditional Andean stimulant. I found it pleasantly helpful. A cup of coca leaf tea is comparable to the affect of tea or coffee (but without the caffeine withdrawal hangover). As of 2012, coca tea is legal in Peru, Bolivia, Colombia, and Ecuador, most commonly served in the Highlands. But don’t bring coca leaves back home, as they are illegal in Brazil, the United States, and most countries outside of South America, despite the low coca alkaloid content. (In the USA, only a few companies are licensed to import and de-cocainize coca leaves such as for pharmaceuticals or soft drinks.)

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Acclimatization Example: Cordillera Huayhuash trek daily elevations

Before trekking in the high altitude Cordillera Huayhuash in Peru 2003, we acclimatized comfortably as follows:

  • A public bus from Lima drove from sea level over a 13,400-foot pass and down to Huaraz at 10,000 feet elevation.
  • We slept for three nights at 10,000 feet in Huaraz and did two higher elevation day trips:
    • We crossed a 14,900-foot pass twice on a bus tour to Chavin at 10,360 feet elevation on the other side of the Andes.
    • We drove to 13,400 feet and hiked downhill 10 miles to Huaraz.

That prepared us well for the following 8-day high altitude trek (the Huayhuash Reverse C Route):

Trek Day: Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8
Highest/Pass 10,660 feet 13,448 15,580 15,370 15,250 15,744 15,700 15,700
Camp Height 10,660 feet 13,448 13,776 14,100 13,940 14,270 14,500 14,400 bus pickup

How high can humans live?

At 18,000 feet you breath only half the oxygen compared to sea level. Research indicates that humans cannot live permanently above an elevation of 18,000 feet without suffering a gradual physiological deterioration that eventually leads to death. Mountaineers who anticipate spending time above 18,000 feet must fatten themselves before the climb to offset their inevitable weight loss.

Workers at the Aucanquilcha sulfur mining camp in Chile lived for years at 17,500 feet above sea level, and ascended each day to work the mine at 18,800 feet. A settlement in Bolivia matched this 17,500-foot record altitude maximum for permanent human habitation. As of May 2003, National Geographic Magazine reports that 16,730-foot La Rinconada, Peru, is the highest permanent human habitation.

Air retains a constant 21 percent of oxygen content (the rest is mostly Nitrogen) throughout all surface altitudes. But as you climb to higher altitudes, the weight of the air column above you decreases, thus lowering air density. As you ascend, the oxygen available per lungfull decreases as follows:

Altitude | Available Oxygen, Compared to Sea Level (average observed at 45 degrees latitude**)

  • 0 feet (sea level) | 100% (base for comparison)
  • 5,000 feet | 80 % of sea level oxygen per lungfull
  • 10,000 feet | 69% of sea level oxygen
  • 15,000 feet | 56% of sea level oxygen
  • 18,000 feet | 50% of sea level oxygen
  • 20,000 feet | 45% of sea level oxygen
  • 29,000 feet | 31% of sea level oxygen per lungfull

**The above figures are averages that apply only to the mid latitudes (45 degrees latitude, North or South). Oxygen available per lungfull also varies slightly by latitude as follows: you will gasp for air about 5 percent harder when climbing at 20,000 feet on Alaska’s Denali (Mount McKinley) than when climbing at the same altitude in the Himalayas. Denali is at 63 degrees north latitude, the Himalaya at 28 degrees north latitude, and the Cordillera Huayhuash at 10 degrees south latitude. Denali rises to 20,320 feet but has the oxygen availability of a 23,000 -foot peak in the Himalayas.

The centripetal force of the earth’s spin shapes the atmosphere (and the earth itself) into an “oblate spheroid”, flattened at the poles and bulging at the equator. At a given altitude, oxygen available per lungfull is highest at the equator (0 degrees latitude) where the atmosphere is deepest (such as at Mount Kilimanjaro, Africa), and lowest at the poles (90 degrees latitude) where the atmosphere is shallowest. 

2 thoughts on “How to acclimatize to high altitude

  1. I went to Maccchu Picchu, Cuzco in June 2014 with my husband and 2 daughters (13 and 17 years old). We had the best experienced ever. WE recommend you to take Ginko Biloba 5 stars with also Vitamin C, Also buy a little bag of Coca leaf and chew it or drink it like a tea. This 3 things are your best best for altitude.

  2. Thank you for this extremely useful information! I will be staying in Huaraz for four weeks beginning in mid-June, and I have been a little worried about the altitude. Prior to reading this I thought that Diamox was the best way to go, but your writing made me remember the undesirable side effects of Diamox that I experienced years ago in Ecuador. I think I will try the ginko biloba instead, and hopefully that combined with a little coca tea will keep me feeling good after my arrival. Luckily, I will have three weeks to acclimate in Huaraz before my trek. Thanks again!

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