About Altitude Sickness

Altitude sickness, often called Acute Mountain Sickness (AMS), is a common issue when you ascend too quickly to high elevations in the Himalayas. It happens because the air gets thinner, with less oxygen available, and your body hasn’t had time to adjust. The key thing to remember; anyone can get it even super-fit athletes, marathon runners, or people who’ve been to high places before. It really depends on how fast you gain elevation, your personal physiology, where you normally live (lowlanders are more at risk), and sometimes past experiences with altitude.

Symptoms usually show up within 6–24 hours after climbing above around 2,500–3,000 meters (8,200–9,800 ft), which is common on Nepal treks like Everest Base Camp or Annapurna.

Common Symptoms of Mild AMS

• Headache (often the first sign, and it can feel like a bad hangover)
• Fatigue or unusual tiredness
• Dizziness or lightheadedness
• Nausea (sometimes with vomiting)
• Loss of appetite
• Trouble sleeping (insomnia)
• Shortness of breath (especially with effort)
• Mild coordination issues or feeling unsteady

If these stay mild and you rest, hydrate, and don’t push higher, most people improve within a day or two. But ignore them and keep ascending, and it can progress to more serious forms: High Altitude Cerebral Edema (HACE) (brain swelling with confusion, severe headache, stumbling, or hallucinations) or High Altitude Pulmonary Edema (HAPE) (fluid in the lungs causing severe breathing trouble and cough). These are emergencies and require immediate descent.

How to Prevent Altitude Sickness (The Practical Rules We Follow on Every Trip)

The good news? AMS is largely preventable if you take it slow and smart. Our itineraries are built around proven acclimatization principles (backed by groups like the Wilderness Medical Society and Himalayan Rescue Association), and we’ve seen them work time and again.

Ascend gradually: The golden rule: Don’t gain more than 500–1000 meters (about 1,640–3,280 ft) in sleeping elevation per day once above 3,000 meters. Many treks build on rest/acclimatization days every few days.

Climb high, sleep low: Hike up higher during the day for extra adaptation, but return to sleep at a lower altitude. This is one of the most effective tricks.

Stay hydrated: Drink 4–5 liters of water (or tea/soup) per day. Dehydration makes everything worse at altitude.

Pace yourself: Walk slowly, take regular breaks, and avoid overexertion. Listen to your body.

Avoid alcohol, tobacco, and sleeping pills: They slow your breathing and make acclimatization harder.

Eat well: Light, carb-rich meals help keep energy up, even if appetite dips.

Tell your guide right away: Even the smallest symptom matters. Our guides do daily health checks (pulse oximeter readings, Lake Louise score) and know when to rest, descend, or use oxygen.

Consider preventive medication: Acetazolamide (Diamox) helps speed acclimatization for many people. The usual preventive dose is 125 mg twice a day (morning and evening), starting 1–2 days before high altitude and continuing for a few days at the top. Some need 250 mg twice daily (talk to your doctor first it can cause tingling in fingers/toes, more frequent peeing, or taste changes). It’s not a substitute for slow ascent, but it’s useful for faster itineraries or if you’ve had AMS before.

Final Thoughts from the Team at Climb in Nepal

We’ve been guiding in these mountains for years, and the number one reason people stay healthy is respecting the altitude; go slow, listen to your body, and communicate openly. Most mild cases resolve with rest and no further ascent. If symptoms worsen, the only sure treatment is descending to a lower altitude (often quickly with our support).

If you’re joining us for Everest Base Camp, Annapurna, a peak climb, or anything above 4,000 meters, we’ll brief you thoroughly on day one and keep a close eye on everyone. Feel free to ask about your specific itinerary or any health concerns we’re here to make sure your Himalayan adventure is safe and unforgettable.

Stay strong, breathe deep, and see you on the trail!