Altitude sickness is treated primarily by descending to a lower elevation, but when immediate descent isn’t possible, a combination of supplemental oxygen and medications can relieve symptoms and prevent the condition from becoming life-threatening. The most commonly used drugs are acetazolamide and dexamethasone for the brain-related forms, and nifedipine for the lung-related form. Which treatment you need depends on how severe your symptoms are and which type of altitude illness you’re dealing with, because altitude sickness is really a family of conditions rather than a single diagnosis.
The Three Conditions People Call Altitude Sickness
When people say “altitude sickness,” they usually mean acute mountain sickness, or AMS, which causes headache, nausea, fatigue, and dizziness after ascending above roughly 2,500 meters (about 8,200 feet). AMS is uncomfortable but not dangerous on its own. The two serious forms are high-altitude cerebral edema (HACE), where fluid accumulates in the brain, and high-altitude pulmonary edema (HAPE), where fluid fills the lungs. HACE can progress from AMS within hours and causes confusion, loss of coordination, and eventually coma. HAPE can develop independently of AMS, typically within the first two to four days at altitude, and presents with breathlessness at rest, a persistent cough, and sometimes pink or frothy sputum. These distinctions matter for treatment because the drugs that work best differ depending on which organ system is affected.
Descent and Supplemental Oxygen
Getting to lower ground remains the single most reliable treatment for all three forms of altitude illness. For mild AMS, even descending a few hundred meters can bring noticeable relief. For HACE and HAPE, descent is urgent and potentially life-saving. Supplemental oxygen, when available, is the other frontline intervention. In a randomized trial at altitude, two hours of oxygen by face mask raised blood oxygen saturation by about 14 percentage points, from roughly 83% to 96%, and symptom scores improved just as rapidly as they did with pressurization in a portable hyperbaric chamber.1Annals of Emergency Medicine. Treatment of acute mountain sickness: Hyperbaric versus oxygen therapy
When descent is impossible and bottled oxygen is unavailable, a portable hyperbaric chamber (often called a Gamow Bag) can simulate descent. The patient is sealed inside an inflatable bag that is pumped up to a pressure mimicking a lower altitude. The same trial found that pressurization raised oxygen saturation by about 7 percentage points and reduced symptoms at a rate comparable to supplemental oxygen, with improvement lasting at least an hour after the patient left the bag.2Annals of Emergency Medicine. Treatment of acute mountain sickness: Hyperbaric versus oxygen therapy The Gamow Bag was specifically designed as a self-contained, portable option for remote expeditions where helicopter evacuation or supplemental oxygen might not be available.3PubMed. A self-contained life support system designed for use with a portable hyperbaric chamber It buys time, but it is not a substitute for descent when HACE or HAPE is present.
Acetazolamide for Prevention and Mild AMS
Acetazolamide is the drug most widely used to prevent and treat mild altitude sickness. It works by blocking an enzyme in the kidneys that normally reabsorbs bicarbonate, which triggers your body to produce slightly more acidic blood. That acidity nudges your breathing centers into a higher gear, so you ventilate more and take in more oxygen, partially counteracting the low oxygen pressure at altitude.4PubMed. Mechanisms of action of acetazolamide in the prophylaxis and treatment of acute mountain sickness In practical terms, it helps your body acclimatize faster than it would on its own.
A well-known randomized trial among Himalayan trekkers found that acetazolamide cut the rate of AMS from 34% in the placebo group to 12%, meaning roughly one in four trekkers who took it was spared an episode they otherwise would have had.5PubMed Central. Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT) Typical preventive dosing is 125 to 250 mg twice daily, started a day or two before ascent. Side effects are usually mild but distinctive: tingling in the fingers and toes, increased urination, and carbonated drinks tasting flat. These annoyances fade after a few days and are actually a sign the drug is working. People with sulfa allergies should discuss alternatives with their doctor, since acetazolamide is a sulfonamide derivative.
Dexamethasone for More Serious Cases
Dexamethasone is a potent corticosteroid that acts quickly to reduce brain swelling and is the drug of choice when HACE is suspected. It also works for prevention and treatment of AMS, though it addresses symptoms without actually helping your body acclimatize the way acetazolamide does. A review of seven prophylaxis studies found that five showed a statistically significant reduction in AMS compared to placebo, while all three treatment studies documented clear benefit once symptoms had already set in.6Journal of Wilderness Medicine. Dexamethasone for prophylaxis and treatment of acute mountain sickness
The effective dose for both prevention and treatment is typically 4 mg every six to eight hours.7Journal of Wilderness Medicine. Dexamethasone for prophylaxis and treatment of acute mountain sickness At very high altitudes above 4,000 meters, higher doses in the range of 8 to 16 mg per day have been studied and appear most effective.8PubMed Central. Dexamethasone for prevention of AMS, HACE, and HAPE and for limiting impairment of performance after rapid ascent to high altitude: a narrative review One important caution: stopping dexamethasone abruptly can cause rebound symptoms. In four studies, significant side effects appeared when the drug was discontinued, possibly related to temporary suppression of the adrenal glands.9Journal of Wilderness Medicine. Dexamethasone for prophylaxis and treatment of acute mountain sickness Because it masks symptoms without promoting acclimatization, climbers who feel better on dexamethasone and continue ascending can find themselves in serious trouble if the drug is stopped or runs out.
Nifedipine and Drugs That Target the Lungs
HAPE requires a different approach because the problem is in the pulmonary blood vessels, not the brain. At altitude, the arteries in the lungs constrict in response to low oxygen, driving up pulmonary blood pressure and eventually forcing fluid into the air spaces. Nifedipine, a calcium channel blocker, relaxes those vessels and lowers pulmonary artery pressure. In a key trial, climbers who took nifedipine had significantly lower pulmonary artery pressures (about 41 mmHg versus 53 mmHg in the placebo group) and lower AMS symptom scores at 4,559 meters.10PubMed. Prevention of high-altitude pulmonary edema by nifedipine
When HAPE has already developed, nifedipine can still help. A study of climbers with established HAPE found that nifedipine treatment, even without supplemental oxygen and while continuing exercise at the same altitude, improved oxygenation, reduced the pressure gradient in the lungs, and led to progressive clearing of fluid.11PubMed. Nifedipine for high altitude pulmonary oedema That makes it a critical option in remote settings where descent or oxygen is delayed.
Tadalafil and sildenafil, drugs better known for treating erectile dysfunction, also lower pulmonary artery pressure and have been recommended as alternatives for HAPE prevention, particularly for longer stays at altitude.12PubMed. Prevention and treatment of high-altitude pulmonary edema However, a systematic review found that neither these drugs nor dexamethasone significantly altered outcomes once HAPE had already developed.13PubMed Central. Systematic Review of the Effects of Phosphodiesterase-5 Inhibitors and Dexamethasone on High Altitude Pulmonary Edema (HAPE) The takeaway is that these drugs are more useful for prevention in susceptible individuals than as treatment for full-blown HAPE, where descent and oxygen remain the priority.
Ibuprofen and Over-the-Counter Options
For people who can’t take acetazolamide or prefer an over-the-counter option, ibuprofen has some evidence behind it. A meta-analysis of three randomized trials covering over 400 subjects found that ibuprofen reduced the incidence of high-altitude headache from about 57% in placebo groups to about 42%. The effect on severe headache was more pronounced: only 3% of those taking ibuprofen had severe headache compared with 10% on placebo.14PubMed Central. Efficacy of ibuprofen on prevention of high altitude headache: A systematic review and meta-analysis The catch is that this evidence applies specifically to headache prevention, not to the broader syndrome of AMS or its serious complications. Ibuprofen won’t help your body acclimatize, and it won’t protect against HACE or HAPE. It’s more of a comfort measure than a true altitude sickness treatment.
The Hydration Question
You’ll hear a lot of advice about “drinking plenty of water” to prevent altitude sickness. The evidence for this is more complicated than the advice suggests. One small study found that fluid intake was associated with lower AMS incidence but couldn’t reach statistical significance due to limited sample size.15PubMed. Acute mountain sickness: influence of fluid intake Meanwhile, a study examining body water balance found the opposite pattern: people who developed AMS actually retained more fluid than those who didn’t, and most of the excess water accumulated in the bloodstream.16PLoS ONE. Association between Body Water Status and Acute Mountain Sickness The researchers argued against “forced” or excessive hydration and suggested that avoiding fluid overload might actually help reduce AMS symptoms.
The practical advice? Stay normally hydrated, especially because you lose more water through breathing at altitude (the air is drier and you’re breathing harder). But pounding liters of water beyond thirst is not a proven strategy and could make things worse. Dehydration at altitude is real, but overhydration appears to be its own risk.
Ginkgo Biloba and Supplements That Don’t Hold Up
Ginkgo biloba is probably the most frequently asked-about herbal remedy for altitude sickness, and the evidence is genuinely contradictory. The large, well-designed PHAIT trial among Himalayan trekkers found that ginkgo was no better than placebo: 35% of the ginkgo group developed AMS compared with 34% on placebo.17PubMed Central. Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT) A smaller trial in Chile, however, found that ginkgo reduced AMS incidence to 0% at 3,696 meters, compared with 54% in the placebo group and 36% with acetazolamide.18PubMed. Ginkgo biloba decreases acute mountain sickness in people ascending to high altitude at Ollagüe (3696 m) in northern Chile
The discrepancy likely comes down to differences in the ginkgo preparations used, dosing schedules, altitude profiles, and study populations. When a large rigorous trial and a small trial disagree, the larger trial usually gets more weight. Most altitude medicine experts do not recommend ginkgo as a reliable preventive strategy. Coca tea, another popular remedy in the Andes, has even less formal evidence behind it. If you’re serious about prevention, acetazolamide is the well-supported option.
Iron supplementation is another idea that has been tested, based on the logic that iron helps red blood cells carry oxygen. A preliminary randomized trial giving intravenous iron before ascent to Lhasa found a lower AMS rate in the iron group (about 26% versus 53%), but the difference was not statistically significant, and the researchers concluded iron supplementation showed no clear protective effect.19PubMed Central. Effect of Intravenous Iron Supplementation on Acute Mountain Sickness: A Preliminary Randomized Controlled Study
How to Use a Pulse Oximeter at Altitude
Portable pulse oximeters have become inexpensive enough that trekkers and mountaineers routinely carry them, and they can be useful for monitoring how your body is coping. At sea level, normal blood oxygen saturation runs between 95% and 100%. At high altitude, values naturally drop, and readings in the high 80s can be normal for someone who is acclimatizing well. The real value of a pulse oximeter is tracking trends over time rather than fixating on any single number. A reading that keeps dropping, or one that is substantially lower than your companions at the same altitude, can be an early warning sign.20PubMed. Pulse oximetry at high altitude
There are limitations worth knowing about. Oxygen saturation at altitude changes quickly with small shifts in breathing or exertion, so a single reading can be misleading. Device accuracy also declines when saturation drops below about 80%, precisely the range where you’d most want reliable data.21PubMed. Pulse oximetry at high altitude For diagnosing HAPE at moderate altitudes (2,700 to 3,500 meters), one study found that a pulse oximetry reading below 86%, combined with a heart rate above 95 beats per minute and a respiratory rate above 21 breaths per minute, was a reasonably reliable diagnostic combination.22PubMed Central. Objective criteria for diagnosing high altitude pulmonary edema in acclimatized patients at altitudes between 2700 m and 3500 m
Prevention Through Slow Ascent
No drug replaces a sensible ascent profile. The most widely endorsed guideline is that above 3,000 meters, you should limit your net sleeping elevation gain to no more than about 300 to 600 meters per day and build in a rest day every one to two ascent days.23PubMed Central. Return to activity at altitude after high-altitude illness The evidence base for these specific numbers is surprisingly thin. A review in High Altitude Medicine & Biology noted that current guidelines are generally similar across organizations but are based on limited evidence and expert consensus rather than large trials. Still, the guidelines appear to work for the majority of altitude travelers, and the authors recommended that rest days be incorporated after any large elevation gain rather than on a fixed schedule.24PubMed. Clinician’s corner: What do we know about safe ascent rates at high altitude?
Repeated exposures to altitude, or even spending time in simulated hypoxic environments before a trip, can help kickstart acclimatization. This approach is sometimes used by mountaineers and military personnel preparing for rapid deployment to high-altitude locations. The core idea is that raising the hypoxic stimulus gradually, whether by climbing slowly or through pre-acclimatization, gives your body time to ramp up red blood cell production, adjust breathing patterns, and make the other physiological shifts that protect against altitude illness.
Why Some People Get Sick and Others Don’t
One of the most frustrating aspects of altitude sickness is its unpredictability. Two people can follow the same ascent profile, take the same precautions, and have completely different experiences. A growing body of research suggests that genetics play a meaningful role. A review of the evidence noted that genomic techniques in recent years have strengthened the case that susceptibility to altitude illness is partly determined by genetic variation.25PubMed. Evidence for and Against Genetic Predispositions to Acute and Chronic Altitude Illnesses One study of soldiers identified a specific gene variant in EDN1 (a gene related to blood vessel constriction) that was associated with higher susceptibility to AMS, alongside physiological predictors like blood oxygen saturation and lung function.26Scientific Reports. EDN1 gene potentially involved in the development of acute mountain sickness
The practical implication is that your past experience at altitude is one of the better predictors of future performance. If you’ve gotten sick before at a given elevation, you’re more likely to get sick again under similar conditions. That doesn’t mean you can never go high, but it does mean you should plan more conservatively, allow more time for acclimatization, and strongly consider prophylactic medication.
Going Back Up After an Episode
If you’ve had altitude sickness and descended to recover, the question of when and how to re-ascend matters. Guidelines recommend that above 3,000 meters, you should limit net elevation gain to no more than 600 meters per day and take a rest day every one to two ascent days, which is slightly more conservative than the standard prevention recommendations for a first ascent.27PubMed Central. Return to activity at altitude after high-altitude illness For mild AMS, you can usually re-ascend once symptoms have fully resolved, as long as you go slowly. After HACE or HAPE, most experts advise waiting longer, allowing full recovery, and being especially conservative on the second attempt.
The temptation to push back up quickly is strong, especially on a guided expedition with fixed schedules and summit windows. But the evidence is clear that a prior episode elevates your risk for the next one, and the medications that mask symptoms don’t change the underlying susceptibility. The most effective thing you can do is give your body time, even if that means changing your itinerary.
Children, Pregnant Women, and People With Chronic Conditions
Most altitude sickness research is conducted on healthy adults, which leaves gaps for some of the people who most need guidance. Children can develop AMS just like adults, but recognizing it is harder because young kids can’t articulate symptoms like headache or dizziness. Fussiness, poor appetite, and unusual sleepiness at altitude should be taken seriously. Acetazolamide can be used in children at reduced doses, though the evidence base is smaller than for adults.
For pregnant women, the general advice is to avoid sleeping above 3,600 meters and to avoid altitudes where supplemental oxygen might become necessary, mainly because low oxygen saturation could affect fetal development. Acetazolamide is typically avoided during pregnancy because its safety profile for the fetus hasn’t been established in large studies. Dexamethasone is sometimes used for serious altitude illness in pregnancy when the risk-benefit calculation favors it, but this is a clinical judgment call. People with chronic lung disease, heart failure, or sickle cell disease face elevated risks at altitude and should consult a physician familiar with altitude medicine before any high-altitude travel.