I don't think the B6 blood testing is very reliable.

The sample can be mishandled and the cells burst releasing it into the serum giving a false elevation. (this happens with potassium commonly).

Or since the test is not done alot, the calibration standard may be degraded from age, and the machine goes lower for a norm, leading to normal levels testing out high.

There is a study for example on autistic children that found elevated B6 levels, in testing. These children did not take vitamins.

Here is our B6 thread:
http://neurotalk.psychcentral.com/thread30724.html

It is really rare for B6 toxicities to occur.

http://lpi.oregonstate.edu/mic/vitamins/vitamin-B6