flying squirrel blood tests for MMA, homocysteine and b12 will not tell you at this point wether you were deficient before you started taking b12. i would keep taking it and see if it continues to help you.

on another point why are you doing a nerve biopsy? that is usually done as a last resort these days and only if certain causes such as vasculitis, are suspected. it causes permanent nerve damage and numbness and can result in permanent pain. check out www.lizajane.com to get an idea about testing for your type of PN.