Altitude Sickness, Health & Safety on the Trail

Altitude is the single biggest health factor on a Nepal trek — bigger than fitness, bigger than the terrain itself. The good news: acute mountain sickness (AMS) is well understood, mostly preventable with correct pacing, and manageable if you know what to watch for.

Recognising AMS

Mild symptoms are common above 2,500–3,000 m and include:

• Headache
• Nausea or loss of appetite
• Fatigue beyond what the day's walking explains
• Dizziness or difficulty sleeping

Mild symptoms are not a reason to panic, but they are a clear signal to stop ascending, rest at your current altitude, hydrate, and tell your guide — every licensed guide on a trek booked through this site is trained to monitor for exactly this.

The warning signs that mean descend immediately

A small number of AMS cases progress to High Altitude Pulmonary or Cerebral Edema (HAPE / HACE), which are medical emergencies. Warning signs include:

• Confusion, loss of coordination, or difficulty walking in a straight line
• Severe breathlessness, even at rest
• A persistent cough, sometimes with pink or frothy sputum
• Symptoms that worsen rather than improve with rest

The only reliable treatment for these signs is immediate descent — sometimes by helicopter evacuation — which is exactly why the altitude limit on your travel insurance policy matters so much (see our Travel Insurance guide).

Prevention: the pacing rule

Ascend no more than roughly 300–500 m of sleeping altitude per day above 3,000 m, with a rest/acclimatisation day for every 1,000 m gained. This single rule prevents the majority of serious AMS cases, and it's already built into every fixed itinerary on this site — it's a large part of why booking a structured departure, rather than rushing your own pace, matters more at altitude than almost anywhere else.

Food and water safety

• Avoid raw vegetables and untreated tap water — stick to well-cooked, hot food, which is standard at every teahouse on the trail.
• Purify all drinking water — tablets, a UV steriliser, or a filter bottle all work; boiled water at teahouses is also safe.
• Limit or avoid alcohol at altitude — it worsens dehydration and can mask early AMS symptoms.
• Drink more than you think you need — 3–4 litres a day is a reasonable target above 3,000 m, since dehydration itself mimics several AMS symptoms.

Sun and cold exposure

UV exposure increases meaningfully with altitude, and snow reflection makes it worse — sunburn and snow blindness are genuinely common trekker complaints. Pair high-SPF sunscreen with UV-rated sunglasses, and don't underestimate how quickly temperatures drop once the sun goes behind a ridge.

A basic first-aid kit worth actually packing

• Blister plasters and antiseptic wipes
• Any personal prescription medication, with several days' buffer
• Rehydration salts
• Diamox (acetazolamide), if prescribed by your doctor in advance as an AMS preventive — this is a prescription decision to make with a doctor before you fly, not on the trail
• A basic understanding of your travel insurer's emergency number, kept somewhere that doesn't rely on phone signal

None of this is meant to be alarming — thousands of trekkers complete these routes safely every season. The trekkers who run into serious trouble are almost always the ones who ignored early symptoms and kept climbing rather than resting.