Preventing Altitude Sickness on Mt. Fuji
Acclimatization strategies:
Acetazolamide (Diamox) — Altitude Sickness Medication:
Acetazolamide (アセタゾラミド, brand name: ダイアモックス *Diamox*) is the evidence-based medication for preventing AMS. It works by stimulating faster breathing, helping the body adapt to lower oxygen levels.
- Dose: 125–250mg twice daily, starting 24 hours before ascent
- Duration: Continue until you have acclimatized or begun descent
- Requires: A prescription from a doctor in Japan or your home country
- Side effects: Increased urination, tingling fingers/toes, carbonated drinks taste flat, rarely photosensitivity
- Contraindications: Sulfa allergy, pregnancy, kidney disease
Where to get acetazolamide in Japan:
Acetazolamide requires a prescription in Japan. Clinics near Mt. Fuji and in major cities can prescribe it if you explain your plans. Some travel medicine clinics in Tokyo and Osaka offer it to mountaineers. Alternatively, obtain a prescription from your home country before departure and bring your supply.
Ginkgo biloba has limited evidence for altitude sickness prevention and is not recommended as a substitute for acetazolamide.
Ibuprofen (400mg 3 times daily) has some evidence for preventing AMS headache and may be taken without prescription; available OTC in Japan.
Mt. Fuji Specific Information
Official climbing season: July to mid-September (山開き to 山閉め)
Starting points (5th Stations):
- Yoshida 5th Station (吉田口五合目) — Most popular; accessible by bus from Kawaguchiko
- Subashiri, Gotemba, Fujinomiya stations — Other routes with varying difficulty
Medical facilities on Mt. Fuji:
- Mountain rescue stations and first aid posts are located at several stations on the Yoshida trail during climbing season
- Mt. Fuji Safety Guidance Center at the 8th Station provides basic medical assistance
- Emergency helicopter rescue (ヘリコプター救助) is available but expensive — travel insurance covering helicopter evacuation is strongly recommended
Emergency number in Japan: 119 (fire and ambulance)
For mountain rescue, 110 (police) also responds to mountain emergencies and coordinates with mountain rescue teams (山岳救助隊).
Climbing regulations:
As of 2024, Mt. Fuji has introduced climbing fees, nighttime closure of the Yoshida trail (to prevent so-called "bullet climbing"), and limits on daily climbers. Check current regulations at the official Fujisan website before your visit.
Treatment of Altitude Sickness
Mild AMS:
- Stop ascending — do not go higher while symptoms are present
- Rest at current altitude
- Hydrate well
- Take OTC pain relievers for headache (acetaminophen or ibuprofen)
- Consider descending 500m if symptoms do not improve within 24 hours
Moderate AMS:
- Descend 500–1,000m immediately
- Continue descent until symptoms resolve
- Take acetazolamide (250mg twice daily) if not already doing so
Severe AMS, HACE, or HAPE:
- Descend immediately and as quickly as possible — this is the most effective treatment
- Call for emergency assistance: 119
- Use supplemental oxygen if available (provided at some mountain huts and rescue stations)
- Portable hyperbaric chambers (Gamow bag) may be available at higher-volume mountain facilities in Japan
Which Department to Visit After Descent
If you descended from altitude but still have symptoms:
- 内科 (Naika) — Internal Medicine: appropriate for follow-up of resolved or mild AMS
- 神経内科 (Shinkeī Naika) — Neurology: if any neurological symptoms (confusion, coordination problems) occurred
- 呼吸器内科 (Kokyūki Naika) — Respiratory Medicine: if chest symptoms or breathlessness occurred
- 救急外来 (Kyūkyū Gairai) — Emergency: for any ongoing severe symptoms
Use Traveler's Hospital to find internal medicine clinics near Mt. Fuji, Hakone, or other mountain areas.
Cost Estimate
Mountain rescue helicopter costs can be extraordinarily high in Japan. Travel insurance with mountain rescue / helicopter evacuation coverage is essential for any serious mountain climbing activity.
Japanese Phrases for Altitude Emergencies
Related Resources
Frequently Asked Questions
Q: How likely am I to get altitude sickness on Mt. Fuji?
A: Studies of Mt. Fuji climbers suggest that 20–40% of climbers experience some degree of AMS, ranging from mild headache to severe symptoms. Risk increases significantly with fast ascent (less than 24 hours total), inadequate hydration, and lack of prior acclimatization. Off-season and night climbing carry additional risks.
Q: Is Mt. Fuji safe to climb for a healthy adult with no altitude experience?
A: Mt. Fuji is accessible to fit, healthy adults, but it should not be underestimated. Proper preparation including appropriate gear, acclimatization strategy, knowledge of AMS signs, and adequate time (ideally 2+ days) significantly reduces risk. The Yoshida trail with a rest at the 5th or 6th Station overnight before the summit push is a safer approach than a direct day trip.
Q: Can children climb Mt. Fuji?
A: There is no minimum age requirement for Mt. Fuji, but children are significantly more susceptible to altitude sickness and fatigue. Many families with children choose to hike partway and return, rather than attempting the summit. If you bring children, watch closely for AMS symptoms which children may not articulate clearly.
Q: Does alcohol affect altitude sickness?
A: Yes. Alcohol impairs acclimatization, causes dehydration, and masks early AMS symptoms. Avoid alcohol for the first 24–48 hours at altitude. Japanese mountain huts (山小屋) serve beer and other beverages — save the celebration for after you descend.
Q: I got altitude sickness on Mt. Fuji — can I try again?
A: Yes, after full recovery. Allow at least 48–72 hours for complete resolution of all symptoms. A better strategy for a second attempt is spending more time acclimatizing at the 5th Station before ascending, and/or taking acetazolamide prophylactically.
Q: Are there other Japanese mountains with altitude sickness risk?
A: Yes. The Japanese Alps have multiple peaks above 3,000m, including Hotaka-dake (3,190m), Yari-ga-take (3,180m), and Ontake-san (3,067m). The Tateyama-Kurobe Alpine Route reaches 2,450m — below the typical AMS threshold but worth noting for susceptible individuals. The risks are generally lower than Mt. Fuji due to typical multi-day trekking approaches, but proper preparation is still important.