Things don’t go always as planned especially if you are landing in a city that sits at 12,000 feet (3.7 kilometers) above sea level.
I had been to Lhasa before and got altitude sickness at the time too but not as bad as this time around.
I thought I was fine but the altitude sickness hit severely the following morning. It is like someone hammering your head or feeling what it might be like the morning after a night of consuming half a dozen drinks too many.
This is nothing new to the hotels here, as most of the guests will get some sort of altitude sickness during their stays.
St. Regis has these huge oxygen bottles on standby, that with some rest cured the headache for a while. It seems that it takes couple of days to acclimatize to higher altitude based on my personal experience.
This hit me once in Cuzco too when I had to throw away my trip to Machu Picchu. I was feeling so terrible that morning with a headache. On my second trip to Cuzco, I arrived after spending couple of nights in La Paz and all was fine during the stay.
St. Regis provides oxygen bottles while Shangri La in Lhasa has an Oxygen Lounge. InterContinental has oxygen switch in the rooms to pump some in (which I have not used).
A headache slows me down as I cannot do anything when feeling that bad. After that I got a stomach bug too that went away. Have to be a bit careful with the toilets here though….