Mild
Headache, mild nausea, breathlessness on stops, slight dizziness. Common above 3,000 m. Rest, hydrate, continue slowly.
Safety
Altitude sickness on Fuji.
At 3,776 m the air holds about 65 percent of sea level oxygen. Most climbers feel it. A few have to turn back. Here is how to avoid being one of them.
Symptoms
What it feels like
Moderate
Persistent headache that paracetamol can't touch, vomiting, lack of coordination. Stop climbing. Descend if it doesn't ease within an hour.
Severe
Confusion, stumbling, breathing trouble at rest, blue lips. Medical emergency. Descend immediately to the fifth station.
Prevention
Five rules that work
Sleep at the fifth station
Arrive in the early afternoon and acclimatize for an hour or two before climbing. The biggest predictor of trouble is rushing up.
Climb slowly
Maintain a pace you could talk in full sentences. If you can't, you're going too fast.
Hydrate constantly
Sip every 15 minutes. Aim for 2-3 L of water across the climb. Dry mountain air dehydrates faster than you think.
Sleep in a hut
Splitting the climb across two days with a hut stop at 3,000 m massively reduces symptom risk.
Skip the bullet climb
Climbing through one night without sleep is the highest-risk style. Avoid it unless you've climbed at altitude before.
Carry an oxygen can
Cheap insurance. A few breaths can ease a mild headache enough to keep moving.
FAQ
Common questions
How common is altitude sickness on Fuji?
Roughly a third of climbers report symptoms. Most are mild and pass with rest. A small percentage have to turn back.
Does Diamox help?
Yes, prescription acetazolamide reduces symptoms when started 24 hours before the climb. Ask your doctor before flying.
Will I be okay if I am fit?
Fitness helps but does not prevent it. Pace and acclimatization matter more than VO2 max.
Can children climb?
Kids above 10 with hiking experience can manage, but they are more prone to altitude sickness. Stop early at symptoms.
Plan