wd- i live at 6200'- and when i visit the low lands, i feel very sleepy and headachey and unmotivated. my brother suggested that my body is used to thinner air- and when i go down in altitude, i super-saturate with o2; causing the malaise. eventually the excess red blood cells will die off- taxing your liver as well. fortunately i'm not usually at low altitude for more than a couple days. when i get home, i feel better.

your body will make more red blood cells to compensate for the lower o2 concentration at higher altitudes. i read a suggestion for dealing with this problem- donate blood right after a high altitude trip.

i have not tried this approach for my sea-level visits, since i am only down there a couple days, and only once a year or so. it would take some "homework" to find a blood donation center & schedule an appointment & etc. - not a convenient job for a 48 hour trip, already scheduled full.

if you try the blood donation, let me know how it goes.