If you have your B12 serum levels checked while you are supplementing with B12, you will get a higher reading. That said, if you want to get a more accurate result, you need to stop the supplement at least four days prior to testing. IMO, I would still continue with the B12 and at some point add in a B complex. The B vitamins need each other and if just supplementing with one, it can mask a deficiency in another.
B12 serum is the least reliable test for b12 deficiency. Here's a thread that discusses it.
http://forums.marrowforums.org/showt...&highlight=b12
Unfortunately, there are doctors, when they don't have an answer, do psych referrals. But there are good, caring doctors out there who will want to help your son and try to figure this out.
Good luck.