Learn how to adjust to high altitude without getting sick (updated 28 February 2018):
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).
The best way to acclimatize above 10,000 feet elevation is to stay hydrated and to “climb high, sleep low.” That is, moderately day-hike to elevations higher than 10,000 feet, but then each night sleep no more than 2000 feet (600 meters) higher than the previous night. Avoid over-exertion for the first 1-2 days after arriving at altitude. According to the Institute for Altitude Medicine at Telluride, “avoid use of alcohol or sleeping agents of the benzodiazepine family, since they both suppress breathing and lower blood oxygen. Other sleeping pills like Ambien or Lunesta do not affect breathing at high altitude and are safe.” 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.
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 or ibuprofen below. According to a significant study in 2010, over-the-counter ibuprofen is just as effective as prescription Diamox (acetazolamide) for prevention of high altitude headache.
Ginkgo Biloba or ibuprofen have fewer side effects than Diamox
If tight trip schedules restrict time available for safe acclimatization, consider ibuprofen or the natural herb Ginkgo Biloba , which are both widely available without a prescription and have 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 may not be as effective as ibuprofen or Diamox. Ginkgo Biloba may interact with some other drugs, but the interaction with Diamox is unknown. Pregnant women and people taking antidepressants should first consult their doctor before using Ginkgo Biloba.
Ginkgo Biloba 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. Other studies
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. My wife says she feels more comfortable at altitude after using Ginkgo Biloba as described above.
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|
|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.