You will not get altitude sickness in Kathmandu. Altitude sickness is common above 2,500 meters in elevation. For reference, the average elevation of Kathmandu is 1,400 meters. That being said, there are four peaks in the Kathmandu valley that are over 2,500 meters: - Shivapuri at 2,800 meters - Phulchowki at 2,795 meters - Nagarjun at 2,825 meters - Chandragiri at 2,551 meters Although these elevations are over the 2,500 meter altitude that high altitude sickness region, you are unlikely to feel anything. This is because you will only be at the altitudes for a short period of time.