Altitude & Acclimatisation: A Trekker’s Guide
Toubkal and Mgoun both climb above 4,000 metres, where the air holds roughly 40% less oxygen than at sea level. Altitude is the single biggest reason people fail to summit — and the good news is that with the right pace and awareness, most healthy trekkers acclimatise well. Here is what every guest should understand before going high.
What happens to your body
As you climb, lower air pressure means less oxygen reaches your muscles and brain. Your body responds by breathing faster and producing more red blood cells — a process that takes days, not hours. This is why we build acclimatisation walks into every high itinerary rather than rushing to the top.
Recognising acute mountain sickness (AMS)
Mild AMS is common above 2,500 m: headache, nausea, fatigue and poor sleep. It usually eases with rest and hydration. The warning signs that demand descent are worsening headache unrelieved by rest, vomiting, confusion, loss of coordination, or breathlessness at rest. Our guides monitor every guest and never push a struggling trekker higher.
The golden rules
Climb high, sleep low where possible. Ascend slowly — the tortoise summits, the hare turns back. Drink three to four litres of water a day. Avoid alcohol at altitude. Eat well even when appetite fades, because carbohydrates fuel acclimatisation. And be honest with your guide about how you feel.
Building fitness before you travel
You cannot pre-acclimatise at home, but strong cardiovascular fitness makes the climb far more enjoyable. In the two months before your trek, build up hill walking, stair climbing and long weekend hikes with a loaded pack. The fitter you are, the more you will notice the scenery instead of your lungs.
Related guides
- The Complete Atlas Mountains Packing Guide
- Mountain Safety & Emergency Protocols
- Toubkal Altitude Sickness: Real Risks, Symptoms & How to Avoid It
- Training & Fitness for Atlas Trekking