You can’t fully guarantee against altitude sickness in the Khumbu — it affects fit and unfit trekkers roughly alike, and there’s no way to predict who gets it. What you can do is cut the risk sharply: follow the acclimatisation schedule, recognize symptoms early, and know exactly when to descend. The cardinal symptom of Acute Mountain Sickness is headache, usually with at least one of dizziness, nausea, fatigue, or loss of appetite, typically starting 2–12 hours after you reach a higher altitude. This guide covers what AMS actually looks like, when it turns dangerous, and the one rule that matters more than any other: descend if it gets worse.
What’s Inside This Guide
- What AMS Actually Feels Like
- When It Turns Dangerous — HACE and HAPE
- Prevention That Actually Works
- Diamox — What to Know Before You Go
- When to Descend — The Rule That Matters Most
- Frequently Asked Questions
- Related Planning Guides
What AMS Actually Feels Like
Per CDC travel health guidance, headache is the defining symptom of Acute Mountain Sickness, usually paired with at least one of: loss of appetite, dizziness, fatigue, or nausea (occasionally vomiting). Symptoms typically start 2 to 12 hours after arriving at a higher altitude, often overnight after the first night at a new elevation. Mild AMS is common and usually manageable — many trekkers feel a dull headache at Namche or Dingboche and it passes within a day. The problem isn’t mild AMS itself; it’s ignoring it or continuing to ascend while it’s getting worse.
When It Turns Dangerous — HACE and HAPE
HACE (High-Altitude Cerebral Edema) and HAPE (High-Altitude Pulmonary Edema) are the two conditions AMS can develop into if ignored, and both are medical emergencies.
| Condition | Key Symptoms | What It Means |
|---|---|---|
| HACE (cerebral) | Confusion, loss of balance, drowsiness, altered mental state — often described as looking like alcohol intoxication | Brain swelling from low oxygen — immediate descent required |
| HAPE (pulmonary) | Chest tightness, persistent cough, breathlessness even at rest, in severe cases coughing blood-tinged sputum | Fluid in the lungs — immediate descent required |
Neither of these waits for a good moment. If a guide or fellow trekker shows signs of HACE or HAPE, descent starts immediately, day or night, regardless of how far you’ve come or how close you are to Base Camp.
Prevention That Actually Works
The single biggest factor is pacing, not fitness. Our itinerary builds in two mandatory acclimatisation days — Namche on Day 3, Dingboche on Day 6 — using the “climb high, sleep low” principle: hike higher during the day, sleep lower at night. We never compress or skip either day. Beyond pacing: drink 3–4 litres of water daily, avoid alcohol above 3,000m, and tell your guide about symptoms as soon as they start rather than waiting to see if they pass on their own. See our full elevation profile guide for the night-by-night altitude breakdown behind this schedule.
Diamox — What to Know Before You Go
Acetazolamide (Diamox) is a prescription medication some trekkers take to help the body adjust faster to altitude. CDC travel health guidance lists a common preventive dose of 125mg every 12 hours, starting the day before ascent and continuing through the first two days at altitude — but this is general public health information, not a prescription for you specifically. Trekkers commonly report a tingling sensation in fingers or toes as a side effect, and it isn’t dangerous on its own. Diamox is prescription-only for a reason: your doctor needs to confirm it’s appropriate for your health history and set the actual dose you should take. Get that conversation done before you fly, not in Kathmandu the night before you leave for Lukla.
When to Descend — The Rule That Matters Most
If AMS symptoms get worse despite resting at the same altitude, descend. For AMS specifically, dropping just 300m in elevation often brings noticeable relief within hours. For HACE or HAPE, don’t wait for “worse” — descend immediately at the first clear signs. This is the one piece of advice on this entire page that matters more than any other: no summit photo, no itinerary schedule, and no amount of money already spent on the trip is worth pushing through worsening altitude symptoms. We train every guide we send into the Khumbu to make this call, and we expect trekkers to trust it when they do.
Frequently Asked Questions
No. Diamox helps your body adjust faster, but it doesn’t replace the acclimatisation schedule. We keep both mandatory rest days in every itinerary regardless of who’s taking preventive medication.
Not reliably. AMS affects fit and unfit trekkers at similar rates, since it comes down to how quickly your individual body adapts to lower oxygen, not your cardiovascular fitness. Fitness makes the walking easier; it doesn’t prevent AMS.
Ordinary fatigue improves with rest and doesn’t come with a headache plus other symptoms like nausea or dizziness. AMS specifically involves that headache-plus-symptom combination, and it tends to appear a few hours after reaching a new altitude rather than gradually building through a long walking day. When in doubt, tell your guide — that’s what they’re there for.
Related Planning Guides
- EBC Trek Package — Full 12-day guided expedition with group pricing from USD 1,039
- Elevation Profile Guide — Night-by-night altitude gain, checked against CDC guidelines
- EBC Trek Difficulty Guide — Which days are hardest, and why
- EBC Trek for Beginners — Honest fitness assessment and training plan
- 12-Day Itinerary Guide — Full day-by-day route breakdown
A Quick, Honest Note Before You Read Further
Everything above is general education for trip planning, not personal medical advice. We’re trekking guides, not doctors. See a physician or travel medicine clinic before you fly — especially to talk through your own heart and lung history, and whether Diamox is right for you and at what dose. If you do get a prescription, follow your doctor’s instructions and the medication’s own packaging over anything written on this page.
Guides Who Take This Seriously, Every Time
The full 12-day package runs from $1,039 per person for groups of 8–12 up to $1,379 solo, with Lukla flights and all permits included — and we train every guide we send out to call for descent the moment it’s needed, without exception. View the full Everest Base Camp Trek package → Questions about altitude risk before you book? Chat with us on WhatsApp →