Everest Base Camp Altitude Sickness: AMS Prevention & Safety

How Real Is the Altitude Risk on EBC?

Altitude sickness is the single biggest risk on the Everest Base Camp trek, far more serious than on a moderate trek like Annapurna Base Camp. The trek climbs to 5,545 m at Kala Patthar, where you breathe roughly half the oxygen available at sea level, and you sleep as high as around 5,160 m at Gorak Shep. Acute mountain sickness (AMS) can affect anyone, regardless of age or fitness.

This is precisely why the standard itinerary builds in two mandatory acclimatisation days, at Namche Bazaar and Dingboche, and limits daily altitude gain. Skipping or rushing these is the most common reason trekkers fail to reach base camp, or get seriously ill.

EBC altitude profile

AMS Symptoms: Mild vs Emergency

Know the difference. Mild AMS is common up high and manageable; the severe forms, HACE (brain) and HAPE (lungs), are life-threatening and demand immediate descent.

The golden rule: if you have symptoms, do not go higher. If they are severe or worsening, descend immediately, even at night. Descent is the cure. People die from ignoring this to "tough it out", tell your guide about any symptoms honestly.

How to Prevent AMS

• Never skip the acclimatisation days at Namche and Dingboche, they do more than anything else to protect you. Follow "climb high, sleep low".
• Ascend slowly. Above 3,000 m, aim to raise your sleeping altitude by no more than about 300–500 m per day.
• Hydrate. Drink 3–4 litres a day, and treat your own water so you keep drinking freely.
• Walk slowly and steadily, "pole, pole" (slowly, slowly). Let your breathing set the pace.
• Avoid alcohol and sleeping pills at altitude; they suppress breathing. Eat well even without appetite, as carbohydrates aid acclimatisation.
• Consider Diamox (acetazolamide) if your doctor advises it. A common preventive dose is 125 mg twice daily, started a day before going high; it speeds acclimatisation. Discuss it with your doctor first, it is a prescription drug and not a substitute for sensible ascent.

Cold, Connectivity & Other Hazards

Altitude is the defining danger, but the high Khumbu brings other hazards to plan for:

• Extreme cold. Nights at Lobuche and Gorak Shep, and the pre-dawn Kala Patthar climb, drop far below freezing. A proper down jacket and a −15 °C sleeping bag (see packing list) are safety items, not luxuries.
• The "Khumbu cough". Dry, cold, thin air commonly triggers a persistent cough; a buff over the mouth and staying hydrated help.
• The Lukla flight. Weather delays add stress and can disrupt acclimatisation plans, build in buffer days, see the best time guide.
• Hygiene. Stomach upsets sap strength at altitude, so treat water, sanitise hands and be careful with food.

Insurance & Emergency Action

• Carry travel insurance with helicopter-evacuation cover valid for trekking to at least 5,600 m. This is non-negotiable on EBC, a heli rescue from the high Khumbu can cost many thousands of dollars, and standard policies often exclude high-altitude activity, so check the wording.
• Keep your insurer's emergency number and policy number accessible, and with your guide.
• If someone shows emergency symptoms, descend immediately while arranging help, losing altitude is the priority, not waiting for a helicopter.
• There are aid posts on the trail, notably the Himalayan Rescue Association clinic at Pheriche, which can assess and treat altitude illness, your guide will know where they are.