Altitude sickness is the most common reason a Nepal trek ends early and it can affect anyone, however fit. The good news: it is largely preventable if you climb slowly, know the warning signs and turn back in time.
In November 2026, Nepal’s Ministry of Health and Food Safety approved the country’s first national standard for managing high-altitude sickness. It covers early detection among tourists, trekkers and climbers, treatment in mountain health posts and rescue and referral. Below we explain what altitude sickness is, how to avoid it on popular treks, what to do if you get sick and what the new standard changes.
Everest Base Camp Trek 16 days with acclimatisation built in Rest days at Namche and Dingboche, plus a spare day for weather See the itinerary →What is altitude sickness?
Altitude sickness is your body struggling to adjust to the lower oxygen levels at height. According to the US CDC ( Center for Disease Control), any unacclimatised traveller who sleeps at 2,450 m (8,000 ft) or higher is at risk and sometimes people are affected lower down.
It comes in three forms:
| Form | What it is | How serious |
|---|---|---|
| AMS (acute mountain sickness) | The common, mild form | Usually improves with rest or descent |
| HAPE (high-altitude pulmonary edema) | Fluid in the lungs | Life-threatening, descend immediately |
| HACE (high-altitude cerebral edema) | Swelling of the brain | Life-threatening, descend immediately |
Kathmandu sits at about 1,400 m, so you won’t feel the altitude in the city. The risk starts once you sleep higher on the trail.
Symptoms to watch for
The CDC describes mild AMS as feeling like a hangover. Headache is the key sign.
AMS (mild): headache plus at least one of the following:
- Loss of appetite or nausea, sometimes vomiting
- Dizziness
- Unusual tiredness
HAPE (lungs), the warning signs:
- Chest congestion and a cough
- Getting out of breath far more than your companions
- Breathlessness even at rest, sometimes coughing up pink or bloody sputum
HACE (brain), the warning signs:
- Confusion or strange behaviour
- Stumbling or loss of balance (try walking heel to toe in a straight line)
- Extreme drowsiness. The CDC warns coma can follow within 24 hours.
If you have a headache at altitude, treat it as altitude sickness until proven otherwise. Tell your guide straight away; hiding symptoms to keep up with the group is how mild AMS turns dangerous.
How to prevent altitude sickness
Go up slowly. The CDC quotes the Wilderness Medical Society rule: above 3,000 m, raise your sleeping altitude by no more than 500 m per night and add an extra acclimatisation night for every 1,000 m you gain.
- Build in acclimatisation days. Spend them hiking higher during the day and sleeping lower (“climb high, sleep low”).
- Never go higher with symptoms. Rest where you are until they clear, or descend.
- Drink enough. Nepal’s new national standard lists gradual ascent, acclimatisation time and adequate fluids as the main prevention steps.
- Skip alcohol for the first 48 hours at altitude, as the CDC advises. Don’t use alcohol or sleeping pills to help you sleep up high.
- Ask your doctor about acetazolamide (Diamox) before you travel. The CDC says it is mainly used to prevent AMS and to speed up acclimatisation. It is a prescription drug, so the decision and dose are for your doctor.
- Choose an itinerary with spare days. A rushed schedule is the biggest risk factor you can control.
Fitness doesn’t protect you: fit hikers often climb too fast. A guide who knows the route sets a sensible pace and spots symptoms early. Read more in Do I Need a Guide to Trek in Nepal?
Nepal Trek Finder Which trek suits your fitness and time? From easy Poon Hill to Everest Base Camp Find your trek →Altitude on popular Nepal treks
How much altitude sickness matters depends on the trek you choose. Altitudes below are from our own trek pages.
| Trek (AKT) | Highest point | Altitude risk | Acclimatisation |
|---|---|---|---|
| Everest Base Camp Trek, 16 days | Kala Patthar 5,545 m (Base Camp 5,364 m) | High | Rest days at Namche (3,440 m) and Dingboche (4,410 m), plus a spare day |
| Motorcycle Tour to Lo Manthang, 12 days | Muktinath 3,800 m | Moderate | Fast ascent by road, so watch for symptoms |
| Ghorepani Poon Hill Trek, 9 days | Poon Hill 3,210 m | Low to moderate | A good first trek |
| Day hikes from Kathmandu: Nagarjun, Kakani, Dhulikhel | Below the risk zone | Very low | A good leg-warmer before a big trek |
Not sure which trek fits your experience and time? Try our Nepal Trek Finder, or compare the two big classics in Annapurna vs Everest.
Nepal Trek Finder Which trek suits your fitness and time? From easy Poon Hill to Everest Base Camp Find your trek →What happens if you get altitude sickness?
The treatment that works best is descent. The CDC notes that AMS improves rapidly after a descent of 300 m or more.
- Mild AMS: stop climbing and rest at the same altitude. If symptoms are gone after a rest day, you can usually continue slowly.
- Symptoms get worse despite rest: go down. Don’t wait for morning if someone is getting worse.
- Signs of HAPE or HACE: descend at once with someone accompanying you and get medical help. In serious cases, a guide arranges a helicopter evacuation to Kathmandu.
Medical help on the trail. The Himalayan Rescue Association runs volunteer-doctor aid posts in the trekking seasons at Pheriche (about 4,370 m) on the Everest route and at Manang on the Annapurna Circuit. Both give talks on mountain illness. Spring climbers and trekkers can also use the HRA Everest ER clinic, which runs at Base Camp from about April to the end of May.
Insurance. Before you book, check that your travel insurance covers trekking up to your highest altitude and includes helicopter rescue. Read the small print: many policies have an altitude limit.
Planning a buffer. Altitude can delay your return by a day or two. Keep a spare day in Kathmandu before your flight home and use it for the city sights. Our small-group tours and last-minute deals are bookable at short notice.
Last minute In Kathmandu today or tomorrow? 50% off Last-minute seats on our small-group tours · From $7.50 per person See available tours →Nepal’s new altitude sickness standard: what changes for trekkers
The Standard Related to Management of High-Altitude Mountain Sickness (2083 BS / 2026) is Nepal’s first national rulebook for diagnosing, preventing and treating altitude illness. It was approved by the Ministry of Health and Food Safety and reported on 6 November 2026.
- Earlier detection of altitude sickness among tourists, trekkers, climbers and local residents.
- Better-equipped mountain health facilities, with a set list of medicines and equipment and trained staff.
- More systematic rescue and patient referral from the mountains.
- Clear roles: the federal government sets policy, budget and monitoring; provinces handle training; local governments run access to care, supplies and referrals.
For trekkers, it should mean more consistent care at health posts along the main routes over time. The reported provisions don’t mention permits or trekking rules and the basics still apply: ascend slowly, acclimatise and descend when in doubt.
FAQ
At what altitude does altitude sickness start in Nepal? The CDC puts the risk from a sleeping altitude of about 2,450 m, sometimes lower. Kathmandu (about 1,400 m) is well below that.
Can I get altitude sickness on the Poon Hill trek? It’s possible but less common. Poon Hill tops out at 3,210 m, so a slow pace and enough water usually keep you comfortable.
How many acclimatisation days does Everest Base Camp need? Our 16-day itinerary has rest days at Namche Bazaar and Dingboche, plus a spare day for weather or health.
Should I take Diamox? Ask your doctor before you travel. The CDC says acetazolamide mainly helps prevent AMS and speed acclimatisation; it does not replace a slow ascent.
Is a helicopter rescue covered by insurance? Only if your policy explicitly covers trekking at your altitude and helicopter evacuation. Check before you book.
Questions about your own plans? Ask us on WhatsApp (+977 98 08 31 32 79), join our Discover Nepal Live Q&A or fill in the Travel Planning Questionnaire.
This article is general travel information, not medical advice. See a doctor before a high-altitude trek.
First trek in Nepal? Ghorepani Poon Hill: Himalayan views up to 3,210 m A 9-day classic Annapurna trek, gentle on altitude View the trek →Sources
- The Himalayan Times: Nepal approves first National Standard for High-Altitude Sickness Management, 6 November 2026
- Onlinekhabar: Health ministry approves standard for managing high-altitude mountain sickness, 6 November 2026
- CDC Yellow Book: High-Altitude Travel and Altitude Illness
- Himalayan Rescue Association: Pheriche aid post, Manang aid post, Everest Base Camp clinic
