What to Pack for High-Altitude Trekking

High-altitude trekking is regular trekking with the difficulty turned up. Above roughly 8,000 feet (2,500 meters), oxygen levels drop, weather gets more violent, temperature swings get more extreme, and the consequences of inadequate gear get serious. Everest Base Camp at 17,500 feet, the Inca Trail to Machu Picchu at 13,800 feet, the Atlas Mountains' Mount Toubkal at 13,600 feet, the Himalayas everywhere — these trips need real gear, not aspirational gear.

Layering for high altitude. Three layers minimum, often four. Base layer: merino wool or synthetic long underwear top and bottom. Mid layer: a fleece or synthetic insulation jacket, plus an insulated puffer for camp and rest stops. Outer layer: a waterproof, windproof shell. For extreme cold (above 16,000 feet, winter trekking), add a heavyweight down parka or a second insulation layer. Cotton anywhere in this system is dangerous — when wet from sweat or weather, cotton accelerates hypothermia.

Bottoms: insulated waterproof pants for cold conditions, plus a base-layer bottom for daytime trekking. Trekking pants with built-in zipped vents work well across temperature ranges. Below 14,000 feet in good weather you can often get away with non-insulated trekking pants and a base layer; above that, insulated pants are the right call.

Footwear is the single most critical piece of high-altitude trekking gear. Mid- to high-cut waterproof hiking boots, broken in over at least 30 miles before the trek. Boots that are perfect on day one and don't have miles on them produce blisters that end the trip. The boots should be one half-size larger than your normal shoe size to allow for thick socks and foot swelling at altitude. Pair with merino wool or synthetic hiking socks (two pairs minimum) and bring blister treatment in your kit.

Hydration and altitude. At 12,000+ feet, you dehydrate faster than at sea level. Plan 4 liters of water per day on active trekking days. Carry electrolyte tablets — Diamox (acetazolamide) prescribed by your doctor specifically for altitude sickness if your trek goes above 12,000 feet, and over-the-counter ibuprofen for headaches. Some trekkers take Diamox prophylactically; others take it only if symptoms appear. Discuss with a travel medicine doctor 4–6 weeks before departure.

Sleep gear matters more than people assume. A sleeping bag rated 15–20°F colder than the lowest expected nighttime temperature (high-altitude nights are often dramatically colder than the published forecasts). A real sleeping pad with R-value 4 or higher — the cold ground is colder than the air. Earplugs and an eye mask for tea-house or hut sleeping where conditions are unpredictable.

Essential medications and altitude kit. Diamox if prescribed. Ibuprofen for headaches. Anti-nausea medication (Zofran is the gold standard but requires prescription; Bonine is over-the-counter and works for many). Anti-diarrheal medication (Imodium). A real first aid kit with blister treatment, elastic bandage for sprains, antibiotic ointment, and any personal prescriptions in original packaging. Above 12,000 feet, descent is the only reliable treatment for severe altitude sickness; medication helps with mild symptoms but won't fix serious cases.

Tech and the cold. Lithium batteries lose capacity in cold; carry batteries in inside pockets against your body. A power bank with at least 20,000mAh capacity for multi-day treks. A headlamp with a red-light mode for night use that doesn't kill night vision. A real camera (phone cameras struggle in cold and at altitude) with extra batteries. A satellite communicator (Garmin inReach Mini, ACR ResQLink) is the single best safety upgrade for any trek above 12,000 feet outside cell coverage.

What to bring that experienced trekkers always carry: a buff or balaclava for face protection from sun and wind, sunglasses rated to category 3 or 4 (snow blindness at altitude is real), heavy-duty sunscreen including for lips, lip balm with SPF, a wide-brimmed hat for daytime sun, a thermos for hot drinks (a hot drink at 14,000 feet is genuinely restorative), and a journal — multi-day treks at altitude produce a different mental state than regular hiking, and many trekkers find writing about it useful.