In this post, you will learn about:
- the most effective way of preventing altitude sickness
- altitude sickness medicine
- natural remedies for altitude sickness
- do’s and don’ts at high altitude
At the end, there’s a Highlights section with a few key points we think are important for you to take away from this post.
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The Most Effective Way of Preventing Altitude Sickness
It’s incredibly simple. Ascend slowly.
Going too high, too fast, is the single most important factor that leads to altitude sickness among those who are susceptible to it.
Hackett, Rennie and Levine in the Lancet Medical Journal AMS [Acute Mountain Sickness] is…highly correlated with speed of ascent…
There is no 100% foolproof way to avoid getting altitude sickness because each individual has a unique response to high altitude based on our genetics. (See more at What is My Risk for Getting High Altitude Sickness?) BUT the great majority of people can avoid getting sick at high altitude by the simple method of ascending gradually.
We are most concerned here with traveling to elevations over 8000 feet/~2500 meters, which is usually considered the start of “high altitude.” Commonly, it is after this point that people who are susceptible may begin to feel unwell (though some people do apparently get altitude sickness symptoms as low as 6500 feet/2000 meters1.) Before we get into what a slow ascent means, exactly, you should know that in this post when we talk about specific altitudes, we’re always talking about your sleeping elevation.
It’s How High You Sleep That Counts
Maybe you have heard the mountain climbing mantra of “Climb high, sleep low.” Climbers know that the elevation that you sleep at is more important than how high you go during the day, in terms of altitude sickness. For reasons better left to altitude experts to explain, sleeping at high altitude deprives your body of adequate oxygen more than a day trip does. For this reason, you need to pay attention to the elevation at which you sleep in Tibet.
Ascending slowly means sleeping at the elevations recommended above. You may drive over a high pass while you are ascending, for example, and this can be okay as long as you descend to a lower elevation to sleep.
What is a “Slow” Ascent, Exactly?
Although there is no perfect rate of ascent that fits everyone, most people can prevent AMS (Acute Mountain Sickness) by following these general rules:
Take at Least 2 Days to Reach 9000 feet/~2700 Meters
- Most importantly, do not go directly from low altitude to a sleeping elevation over 9000 feet/~2700 meters in one day.
- The recommendations vary for a good elevation to spend your first night:
- Some sources recommend planning to sleep at least one night (and ideally 2-3 nights) somewhere between ~6500 feet/2000 meters and 9000 feet/~2700 meters on the way up.
- The US CDC specifically recommends acclimatizing for a few days at 8000-9000 feet/ ~2400-~2700 meters before proceeding to a higher altitude. But they also note that some people begin to get altitude sickness at 8000 feet/~2400 meters, so it stands to reason that spending the first night, say between 7000-8000 feet/~2100-~2400 meters, and a second night between 8000-9000 feet/~2400-~2700 meters would be helpful.
After You Reach 9000 feet/~2700 Meters…
Assuming you have taken at least two days to get to 9000 feet/~2700 meters:
- Do not increase your sleeping altitude more than ~1500 feet/ ~500 meters per night.
- Spend an extra night at the same elevation every ~3000 feet/~1000 meters. Generally speaking, this means that you would have a rest day (an extra night at the same elevation) every 3 to 4 days.
Hypothetical Example of a Slow Ascent for a Tibet Traveler
- Before entering Tibet, a night at sea level
- Night 1 in Tibet at 7500 feet/ ~2300 meters
- Night 2 at 8200 feet/ ~2500 meters
- Night 3 at 8200 feet/ ~2500 meters
- Night 4 at 9700 feet/~3000 meters
- Night 5 at 11,200 feet/~3500 meters
- Night 6 at 12,700 feet/~3800 meters
- Night 7 at 12,700 feet/ ~3800
- Night 8 at 14,200 feet/ ~4300
We are posting this hypothetical example for a few reasons. We want to:
- Make the acclimatization rules as easy as possible to understand and to apply to your own trip.
- Show you that the common flights to Lhasa (from Beijing or Chengdu, for example) are shockingly fast ascents compared to this ideal rate of ascent. At 11,975 feet/~3650 meters, ascending to Lhasa slowly would put you there somewhere between night 5 and 6, not at night 1!!
- Bring attention to the fact that this hypothetical example of an ideal rate of ascent is nothing like what the great majority of travelers to Tibet actually do. At the moment it is very rare to find a Tibet trip that ascends like this. It is actually very challenging to find slow ascent routes, especially to the popular destinations in Central Tibet.We hope to open up a conversation in the Tibet travel world that encourages safer, slower ascents. It won’t be easy, for reasons that we will discuss more in future posts in this series on altitude sickness, but we do think it’s important that travelers be given more tools to make better decisions about the itineraries they choose for travel to and in Tibet.
In another post in this series – Itineraries for Preventing Altitude Sickness in Tibet – we offer itineraries that would allow the best chance of acclimatization. We know there are some out there, and hope to shine a light on the ones that would best allow you to feel well on your trip.
For the moment, let’s continue with some secondary methods for avoiding altitude sickness.
Altitude Sickness Medicine
By far the best way of preventing altitude sickness is to ascend gradually. If you have no choice but to ascend too high too fast, you may want to consider taking medication.
If you are at moderate or high risk of getting altitude sickness (learn more about your risk here), you may want to discuss with your doctor the possibility of taking Diamox (the brand name for the drug acetazolamide) unless you have sulpha allergies.
Acetazolamide has been well studied in clinical trials and is widely considered to be effective in preventing altitude sickness and speeding acclimatization2. It is by far the most commonly prescribed medicine for the prevention of altitude sickness.
It is important to note that we are not medical experts and that it is important that you consult with your doctor before undertaking any course of action related to altitude sickness medication!!
Here’s a quick recap of the factors that put you at moderate or high risk of getting altitude sickness. For the people in the moderate risk category, according to the US CDC, taking preventative acetazolamide “would be beneficial and should be considered.” For people in the high risk category, it is “strongly recommended.”
Moderate Risk: Acetazolamide Would Help and Should be Considered
- People who have not had altitude sickness before ascending to between 9200 feet/2800 meters and 11,400 feet/3500 meters in one day.
- People who have had AMS previously, and who ascend to 8200-9200 feet/2500-2800 meters in one day.
- Anyone ascending over 1600 feet/500 meters a day (in sleeping elevation) above 11,400 feet/3500 meters.
High Risk: Acetazolamide is Strongly Recommended
- Anyone ascending to more than 11,400 feet/3500 meters in one day. (Flying to Lhasa from Chengdu, for example)
- Anyone who ascends more than 1600 feet/500 meters per day in sleeping elevation at altitudes above 11,400 feet/3500 meters.
- People who have had AMS previous, and who ascend to ~ 9200 feet/2800 meters or more in one day.
- Anyone who has already had HAPE or HACE. (Get the definition of AMS, HACE and HAPE here.)
When and How is Diamox Typically Taken?
The Wilderness Medical Society Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness notes that the “recommended adult dose for prophylaxis is 125 mg twice daily… While higher doses up to 500 mg daily are effective at preventing AMS, they are associated with more frequent and/or increased side effects, do not convey greater efficacy, and, therefore, are not recommended for prevention.” “Prophylaxis” in this case refers to taking the Diamox before you ascend.
The common side effects of Diamox are:
- Tingling in your fingers and toes
- Increased urination
Acetazolamide is typically started the day before you start ascending, and discontinued either after reaching a high point and having begun descent, or, in the case when ascending to one elevation and remaining there, after 2-3 days at the high altitude. (A major question we have not been able to get answered is when to stop taking Diamox if you are ascending and descending over the course of your first week, as you do when driving through Kham and Amdo. We continue to search for this.)
There is much more that is known about taking Diamox for altitude sickness and we will write a full post on it in this series. If you are considering taking it, it is critical to first consult your doctor, since this discussion is just a quick summary. One important issue that we we have not discussed, for example, is that you need to determine if you might be allergic to Diamox/acetazolamide. Another is that Diamox is useful as a preventative against AMS and HACE, but not HAPE.
Other Altitude Sickness Medicine
While Diamox is the most commonly prescribed altitude sickness medicine, there are a number of other medicines that are also used for prevention against AMS, HACE and HAPE (Learn about these three conditions here).
Generally speaking, these medications have more specialized uses and we will only list them here for your information. You can learn more about them from the Resources links at the bottom of this post.
- Dexamethasone: For those who may have an allergic reaction to acetazolamide. Generally more used as a treatment.
- Nifedipine: For prevention of HAPE in people particularly susceptible to it.
- Tadalafil: For HAPE
- Sildenafil: For HAPE
- Salmeterol: For HAPE
If you are going very high in remote places, you might want to talk to your doctor about getting prescriptions for medications that treat HACE and/or HAPE. Some of the medications we have discussed are also used as treatment for existing altitude sickness, but we will not discuss that here as we are only focusing on prevention in this post. (For more about medications used for treatment of altitude sickness, see the “Medications” section of the US CDC page on altitude sickness.)
A July 2015 article on the US CDC website notes that “Ibuprofen 600 mg every 8 hours was recently found to help prevent AMS, although it was not as effective as acetazolamide. However, it is over-the-counter, inexpensive, and well-tolerated.”
Natural Remedies for Altitude Sickness
There are a number of herbal or homeopathic remedies being used by travelers for altitude sickness. Unfortunately, there is not yet enough reliable clinical evidence that supports their efficacy or use.
Here’s a partial list of some of the natural remedies now in use:
- Coca leaves
- Gingko Bilabo
- Chinese herbal medicines, including Fufang yi hao pills, Sheng nao kang pills, Shu li kang capsules, Xing nao jing injection, and Danhong injection.
Some of the remedies hold promise, but in all cases more rigorous testing is required to confirm popular opinion and anecdotal evidence.
A good example is the supplement Ginkgo Biloba, which is popularly thought to be helpful in preventing altitude sickness. However, one of the very best evidence-based resources, the Wilderness Medical Society Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness, notes that:
“Although several trials have demonstrated a benefit of Ginkgo in AMS prevention, several negative trials have also been published. This discrepancy may result from differences in the source and composition of the Ginkgo products. Acetazolamide is considered far superior prophylaxis for AMS prevention.” (For citations, see the full article at the link.)
Another example discussed in the very reputable Wilderness Medical Society Consensus is coca leaves. “Chewed coca leaves, coca tea, and other coca-derived products are commonly recommended for travelers in the Andes for prophylaxis, and anecdotal reports suggest they are now being used by trekkers in Asia and Africa for similar purposes. However, their utility in prevention of altitude illness has never been systematically studied, and they should not be substituted for other established preventive measures described in these guidelines.”
Note: It has been reported that coca leaves may be drug testable as positive for cocaine.
Chinese Herbal Medicines
Another example is Chinese herbal medicines for altitude sickness. An evidence-based study, Chinese Herbal Medicine for Acute Mountain Sickness: A Systematic Review of Randomized Controlled Trials, determined that “No firm conclusion on the effectiveness and safety of Chinese herbal medicine for AMS can be made. More rigorous high-quality trials are required to generate a high level of evidence and to confirm the results.”
Given travelers’ high interest in more natural altitude sickness medicines, we hope that more studies will be undertaken to help provide evidence-based guidance. Until then, diamox is considered the medicine of choice if you absolutely cannot ascend slowly.
Do’s and Don’ts at High Altitude
We’re certainly no experts about this, and we don’t understand the science behind any of these, but here are what altitude experts seem to agree on for your first 2-3 days at high altitude
- Drink alcohol
- Engage in strenuous exercise (Like climbing the steps of the Potala in Lhasa.)
- Eat plenty of carbs, to aid ventilation and efficient use of oxygen.
- Drink plenty of water (but not too much – the benefits of forced hydration is a myth.)
More in the Series on High Altitude Sickness
This is the third in a series of posts addressing our readers’ questions and fears about altitude sickness. If you have not read the first two posts in the series, please take a minute and check them out now to learn some basics about the disease:
- Altitude Sickness Prevention in a Nutshell
- Altitude Sickness in Tibet: How Bad are the Symptoms?
- How to Avoid Altitude Sickness
- Itineraries for Preventing Altitude Sickness
- Wilderness Medical Society Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness
- The U.S. Centers for Disease Control and Prevention’s CDC Health Information for the International Traveler, chapter on altitude sickness
- Himalayan Rescue Association Nepal
- International Society for Mountain Medicine (ISMM)
Resources About Medications
- Both tadalafil and dexamethasone may reduce the incidence of high-altitude pulmonary edema: a randomized trial.
- Medications section of the US CDC pages on altitude sickness
- American Family Physician pages on altitude sickness