At what altitude does sickness usually start?

Most people notice symptoms around 8,000 ft (2,500 m), but highly sensitive individuals can feel unwell as low as 6,500 ft.

Can I fly directly to La Paz, Bolivia (13,400 ft) and be okay?

Flying to very high cities poses a high AMS risk; plan to rest for 48 hours, hydrate, and consider preventive medication after speaking with a clinician.

Does caffeine worsen altitude sickness?

Moderate coffee or tea is generally safe; there’s no strong evidence it worsens AMS, but excessive caffeine can dehydrate you.

How long do symptoms last if I stay at the same altitude?

Mild AMS usually improves within one to three days with rest and hydration; if it doesn’t, descend.

Is it safe to use sleeping pills at altitude?

Sedatives suppress breathing and can lower nighttime oxygen levels, so most clinicians advise against them above 8,000 ft.

Can children get altitude sickness?

Yes—children show similar symptom patterns to adults, and because they may not verbalize headache, watch for unusual fatigue or loss of appetite.

Will a fitness mask help me acclimatize before travel?

Training masks simulate breathing resistance, not low oxygen; they do not prevent altitude sickness.

What vaccinations do I need for high altitude?

No vaccine prevents AMS, but routine immunizations and, depending on destination, typhoid or hepatitis A may be advised.

Should I carry supplemental oxygen on a trek?

For climbs above 15,000 ft or remote routes without quick evacuation, a lightweight oxygen cylinder or concentrator is prudent.

Altitude sickness explained: why your body reacts at high elevations and what to do about it

What exactly is altitude sickness and who gets it?

Altitude sickness is your body’s stress response to thinner air. The lower oxygen content forces organs to work harder, triggering symptoms within 6-24 hours of arrival. Anyone can get it—even elite athletes—if they climb too high, too fast.

AMS usually starts above 8,000 ftLarge studies of trekkers in the Andes show a 25 % incidence of AMS at 9,000 ft and 45 % at 11,000 ft.
Rate of ascent is the strongest risk factorClimbing more than 1,600 ft (500 m) per day doubles AMS risk compared with slower ascents.
Past AMS predicts future episodesUp to 80 % of people who once had AMS will experience it again if they repeat the same fast ascent profile.
Physical fitness does not protect youMountaineering registries confirm no difference in AMS rates between marathon runners and sedentary travelers when ascent speed is identical.
Symptoms often develop within the first 6–10 hoursThe NHS notes that signs of acute mountain sickness such as headache, nausea and sleep trouble usually begin 6–10 hours after reaching a high altitude. (NHS)
Severe forms (HAPE & HACE) can be life-threateningCleveland Clinic warns that high-altitude pulmonary edema and high-altitude cerebral edema are serious complications of altitude sickness that require emergency care. (CC)

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Which altitude sickness symptoms mean you should seek emergency help?

Most headaches resolve with rest, but some signs point to life-threatening high-altitude cerebral edema (HACE) or pulmonary edema (HAPE). Act quickly—delay can be fatal within hours.

Inability to walk a straight lineNew loss of balance or confusion signals brain swelling; immediate descent of at least 3,000 ft is critical.
Persistent vomitingMore than two episodes in six hours dehydrates you and indicates worsening AMS.
Resting breathlessnessBreathing fast while sitting or a pulse oximeter reading under 75 % at altitude suggests HAPE.
Bluish lips or nailsCyanosis means severe oxygen shortage; supplemental oxygen and evacuation are required.
Rapid deterioration overnightSudden decline during sleep is common in HACE. The team at Eureka Health notes, “Never wait until morning—night-time decline at altitude is a red flag for immediate descent.”
Pink, frothy cough points to fluid-filled lungsA cough that brings up white or pink frothy sputum is a hallmark of HAPE; anyone who develops it needs supplemental oxygen and rapid descent. (WebMD)
Severe altitude edema can kill within hoursAPEX notes that both HAPE and HACE "can be fatal within hours," underscoring the need for immediate evacuation when red-flag symptoms appear. (APEX)

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Why does thinner air make you sick in the first place?

At 10,000 ft air pressure drops roughly 30 %, so every breath delivers fewer oxygen molecules. Your body compensates by hyperventilating and increasing heart rate, but fluid shifts and vessel leakage can follow.

Lower barometric pressure lowers blood oxygenArterial O₂ saturation falls from sea-level 97 % to about 88 % at 10,000 ft in average adults.
Fluid leaks from capillariesHypoxia makes blood vessels leaky, leading to brain swelling (HACE) or lung fluid (HAPE).
Genetics influence susceptibilityVariants in the EPAS1 gene—common in Tibetan highlanders—improve oxygen usage and lower AMS risk.
Acclimatization reverses hormonal spikesWithin 48 hours the kidney dumps bicarbonate, normalizing blood pH and easing symptoms, explains Sina Hartung, MMSC-BMI: “The kidney’s response is why a rest day every 2,000 ft makes such a difference.”
Roughly 25 % of people who ascend above 8,000 ft get acute mountain sicknessCleveland Clinic estimates that about one in four travelers develops AMS when they reach elevations over 8,000 ft without adequate acclimatization. (CCF)
Initial symptoms often appear within 6–24 hours at altitudeWebMD reports that headache, nausea, dizziness and sleep disturbance typically begin during the first day after arrival, mirroring the time course of falling blood-oxygen levels. (WebMD)

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How can you manage mild altitude sickness on your own?

If symptoms are mild and you are below dangerous thresholds, simple measures often prevent progression and keep you on the trail.

Stop climbing and rest for 24 hoursStaying at the same elevation allows acclimatization; 80 % of mild cases resolve with a rest day.
Hydrate with 3–4 liters of fluidThinner, drier air increases insensible water loss by up to 1 liter per day.
Use over-the-counter pain relief cautiouslyIbuprofen 600 mg every 8 hours reduced headache scores by 45 % in randomized trekkers, but it can irritate the stomach at altitude.
Avoid alcohol and sleep aidsBoth depress breathing and worsen nighttime oxygen saturation.
Monitor oxygen saturation twice dailyA drop of more than 5 % from baseline is an early warning to stop ascent, notes the team at Eureka Health.
Descend promptly if symptoms worsen at restThe CDC recommends moving to a lower elevation when mild altitude sickness fails to improve or starts to get worse despite a rest day, as descent is the quickest way to halt progression. (CDC)
Expect recovery within 12–72 hours at the same altitudeKaiser Permanente notes that with rest and no further ascent, most mild cases clear in about 12 hours to 3 days, so patience before climbing higher is important. (KP)

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What tests or prescription drugs come into play for altitude sickness?

Lab work is rarely needed on the mountain, but certain diagnostics and medications can be lifesaving before, during, and after high-altitude exposure.

Pulse oximetry is the frontline testPortable finger devices weigh 2 oz and give instant readings; values under 80 % warrant intervention.
Chest ultrasound detects HAPE earlyMobile ultrasound shows B-lines (fluid) before X-ray changes and guides evacuation decisions.
Acetazolamide helps you acclimatizeA 125 mg twice-daily dose started 24 hours before ascent cuts AMS incidence from 47 % to 21 %, but it is a prescription drug and not right for everyone.
Dexamethasone treats brain swellingEmergency dosing (8 mg once, then 4 mg every 6 hours) improves HACE symptoms within six hours yet carries side effects like mood changes.
Portable oxygen concentrators bridge descentFlow rates of 2–4 L/min raise SpO₂ above 90 %, buying time for evacuation.
Ibuprofen cuts the odds of AMS three-foldA field trial at 12,570 ft found hikers taking 600 mg of ibuprofen every 8 hours were three times less likely to develop acute mountain sickness than those on placebo. (NPR)
Nifedipine remains a pharmacologic back-up for HAPEKaiser Permanente notes that physicians may prescribe nifedipine to lower pulmonary artery pressure and improve oxygenation when high-altitude pulmonary edema is suspected and descent or oxygen alone is insufficient. (KP)

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How can Eureka’s AI doctor guide you before and during a high-altitude trip?

Planning reduces risk, and real-time advice prevents small problems from escalating. Eureka’s AI supports both.

Personalized ascent profilesEnter your planned itinerary and the AI calculates daily elevation gain, flagging risky segments.
Symptom triage in minutesDescribe your headache, and Eureka classifies severity using validated Lake Louise criteria.
Medication suitability checksThe AI reviews your allergies and kidney function before suggesting acetazolamide, a process later verified by the Eureka medical team.
Offline guidance works without internetDownloaded protocols offer step-by-step instructions if you lose connectivity above tree line, notes Sina Hartung, MMSC-BMI.

What makes Eureka’s AI doctor a safe companion for altitude concerns?

Eureka blends automated intelligence with human oversight, so users get quick answers that remain clinically sound.

Medical team reviews every prescription requestOnly licensed physicians finalize orders, keeping safety central.
High user satisfactionTrekkers who consulted Eureka last season rated the experience 4.7 out of 5 stars for clarity of advice.
Privacy by designAll symptom logs are end-to-end encrypted and stored anonymously.
Continuous monitoring toolsLink your pulse oximeter and Eureka alerts you if saturation trends downward overnight.
24/7 global availabilityWhether you are in Colorado, Nepal, or the Alps, the AI chat remains accessible for urgent questions, emphasize the team at Eureka Health.

Altitude sickness explained: why your body reacts at high elevations and what to do about it

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Key Takeaways

What exactly is altitude sickness and who gets it?

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Become your owndoctor 🩺

Which altitude sickness symptoms mean you should seek emergency help?

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Why does thinner air make you sick in the first place?

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How can you manage mild altitude sickness on your own?

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What tests or prescription drugs come into play for altitude sickness?

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How can Eureka’s AI doctor guide you before and during a high-altitude trip?

What makes Eureka’s AI doctor a safe companion for altitude concerns?

Frequently Asked Questions

At what altitude does sickness usually start?

Can I fly directly to La Paz, Bolivia (13,400 ft) and be okay?

Does caffeine worsen altitude sickness?

How long do symptoms last if I stay at the same altitude?

Is it safe to use sleeping pills at altitude?

Can children get altitude sickness?

Will a fitness mask help me acclimatize before travel?

What vaccinations do I need for high altitude?

Should I carry supplemental oxygen on a trek?

References