Just make sure you're well-hydrated. The biggest change in atmospheric pressure is in the first 5,000 feet, actually.....beyond that, the change is more gradual.
FWIW, I've been ok at 7,000 feet, and spent a few days there....then spent a few days at a lower elevation, and then went to 10,500 feet of elevation (kinda ran up Lassen Peak in NorCal). I got a bit of a headache due to the fast ascent and I was slightly dehydrated. Performance-wise I was fairly ok.
__________________
2016 Trek 520 (54cm) touring bike for sale - never ridden. Message me for photos/details.