What is AMS? Know it before going to high altitude area.

Acute Mountain Sickness (AMS) is the most common form of altitude illness, occurring when you ascend too quickly to elevations typically above 2,500 m (8,200 ft). Your body needs time to adopt to sudden reduced air pressure and lower oxygen levels at high altitudes. Its symptoms ranging from mild headaches to life-threatening brain or lung swelling.

What Causes AMS?

Reduced oxygen availability. Each breath at 3,000 m delivers only about 70 % of the oxygen you get at sea level.
Rapid ascent. Flying or driving straight to high-altitude destinations gives your body little time to adjust.
Individual variability. Age, fitness or past altitude experience do not reliably predict who will develop AMS. Anyone can be affected.

Symptoms

Mild (Common. often self-limiting)

Typically appear 6-24 hours after ascent and may resolve within 1–3 days if you rest and stop going up.

Headache.
Nausea, vomiting or loss of appetite.
Dizziness or lightheadedness.
Fatigue or weakness.
Trouble sleeping.

Managing Mild Symptoms

Stop ascending and rest at the same elevation until you feel better.
Hydrate and eat small, frequent meals.
Light activity such as gentle walking is acceptable, but avoid uphill climbs.
Symptoms often improve with proper acclimatization within 1–3 days.

Severe (Medical Emergency)

Require immediate descent and professional care.

Ataxia (loss of coordination) or confusion.
Breathlessness at rest or persistent cough (sign of HAPE).
Inability to walk or stand.
Cyanosis (bluish lips, tongue or fingernails).
Seizures or impaired consciousness (sign of HACE).

Responding to Severe Symptoms

Descend immediately, ideally by 300–1,000 m, until symptoms improve.
Seek medical assistance: oxygen therapy or portable hyperbaric chambers can be lifesaving.
Do not delay descent. HACE and HAPE can progress rapidly to fatal complications.

Incidence and Key Facts

2,500 m: ~20–25 % of travelers develop AMS.
3,000 m: ~40 % incidence.
4,000 m: 25–50 % of hikers will experience AMS when ascending at a moderate pace.
4,500-5,000 m: Prevalence peaks around 51 % among trekkers in this range.
Above 5,000 m: Reported AMS rates are about 34 %, likely lower due to self-selection of experienced climbers.
High-Altitude Cerebral Edema (HACE): Occurs in approximately 1–2 % of individuals ascending to 4,000–5,000 m.
High-Altitude Pulmonary Edema (HAPE): Affects 0.2–6 % at 4,500 m.

Prevention Strategies

Ascend Gradually
- Above 2,500 m, limit daily sleeping-altitude gains to ≤ 300 m and include a rest day every 2–3 days .
“Climb High, Sleep Low”
- If trekking, reach higher elevations during the day but return to a lower campsite to sleep.
Pre-Acclimatization
- Spend 1–2 nights at 2,500–3,000 m before moving higher.
Hydration & Nutrition
- Drink 3–4 L of water daily; avoid alcohol and excessive caffeine .
- Eat light, high-carbohydrate meals to fuel increased energy needs.
Pace Yourself
- Avoid strenuous activity during the first 24–48 hours at a new altitude.
Monitor Your Oxygen
- Use a pulse oximeter. resting saturations below 85 % need extra caution.

Additional Tips for High-Altitude Travel

Plan rest days into your itinerary every 600–900 m of elevation gain.
Travel in pairs or groups and perform daily health checks.
Know local medical facilities along your route.
Carry essential gear: pulse oximeter, thermometer, emergency oxygen if available, clear evacuation plan.

You should avoid high altitudes if you have heart or lung disease.

Also read: Tips to acclimatize easily in Himalayas and avoid AMS