Altitude sickness, also known as Acute Mountain Sickness (AMS), is a common and potentially serious conditions that occurs when you ascend to high elevations too quickly. It happens because the air pressure drops as you gain altitude, meaning each breath contains less oxygen than you’re used to at sea level. Your body needs time to adapt; a process called acclimatization.
A vital consideration for trekkers is that being fit offers no protection. Even the fittest among us can get altitude sickness, while those less fit may not feel any effects at all. Altitude sickness normally occurs above 2,500 m (8,000 ft), but some people may feel symptoms at as low as 2,000 m.
The golden rule of hiking at high-altitude trekking is simple: “Climb high, sleep low”. This means you should spend your days gaining elevation (to help your body adapt) but descend to a lower altitude for sleeping. This strategy dramatically reduces your risk of developing AMS and its more dangerous forms.
Common Symptoms of Altitude Sickness
Altitude sickness exists on a spectrum, ranging from mild discomfort to life-threatening emergencies. Understanding the difference can save your life.
Mild AMS (Acute Mountain Sickness) – Very Common
- Headache: Often the first and most universal symptom. It typically feels like a throbbing pain, worsened by bending over or exertion. Usually appears within 6-12 hours of arriving at a new altitude.
- Fatigue & Weakness: A sudden, unusual tiredness that feels disproportionate to your physical activity.
- Dizziness & Lightheadedness: A feeling of unsteadiness, especially when standing up quickly.
- Loss of Appetite & Nausea: You may not feel like eating, and even the smell of food can be unappealing.
- Sleep Disturbances: Trouble falling asleep, frequent waking, or vivid, strange dreams.
Moderate AMS – Warning Signs (Do Not Ascend Further)
- Symptoms from mild AMS that do not improve after 24 hours at the same altitude.
- Worsening headache that does not respond to painkillers.
- Persistent nausea and occasional vomiting.
Severe AMS – Emergency (Descend Immediately!)
These symptoms indicate HACE (high Altitude Cerebral Edema) or HAPE (High Altitude Pulmonary Edema); both are medical emergencies:
- Confusion, irrational behavior, or extreme drowsiness.
- Loss of coordination (ataxia): Inability to walk in a straight line or perform simple tasks.
- Blue or gray lips/fingertips (cyanosis): A sign of severe oxygen deprivation.
- Coughing up pink, frothy phlegm: A hallmark of HAPE (fluid in the lungs).
- Shortness of breath even at rest.
Self-Assessment Tip: If you experience any moderate or severe symptom, Do not wait- you should immediately inform your guide and begin immediately. Descending just 300-500 m can be life-saving.
Preventions of Altitude Sickness
“Prevention is better than cure” is true even for altitude sickness. Here are the most effective strategies to keep your healthy on your Himalayan trek.
- Gradual Acclimatization (The Most Important Rule)
Use the 300-500 m Rule which means to not increase your sleeping elevation by more than 300-500 m (1,000-1,600 ft) per night. Also remember to include at least one day for acclimatization for every 1,000 m gained. Lastly, during acclimatization walks, hiking to a higher point and returning to sleep at a lower altitude.
- Proper Hydration
Hydration is very important especially at higher altitude, especially if you’re sweating heavily. Make sure to avoid caffeine and alcohol, as they cause dehydration and suppress breathing patterns during sleep.
- High-Carbohydrate Diet
Focus on eating meals rich in complex carbohydrates (rice, pasta, bread, potatoes). Carbohydrates require less oxygen to metabolize than fats or proteins, giving your body more energy for acclimatization.
- Medication (e.g. Diamox (Acetazolamide))
Diamox is a prescription medication that speeds up the acclimatization process. Always consult with your doctor before taking any medication, especially if you have any condition or taking any other medications.
- Avoid Alcohol, Sleeping Pills, and Heavy Meals
One again, avoid alcohol at high altitude as it suppresses breathing and increases the risk of AMS. This is also the risk of taking sleeping pills (like Ambien) that can even suppress symptoms. Also, stick to smaller, frequent meals instead of heavy, greasy meals that are harder to digest at altitude.
- Pre-Acclimatization
If possible, spend 1-2 days in Kathmandu (1,400 m) or similar moderate altitude before heading to higher elevations. This gives your body a head start on adapting.