I've been wondering the very same thing about Vit B1 and B6 specifically. What about the total picture rather, than an ad hoc look at B12 and Vit D, which can be very equivocal anyway.

Is it even worth asking for these things to be looked at?

Also what about the phospholipids (such as phosphatidylserine and phosphatidylcholine etc) - how complicated are they to test for? And what are their implications?

At one point, back in 2003, John did meet with a nutritionist who mentioned that you can have your white blood cell analyzed for a good assessment of the B vitamins. This was in response to us telling her that he came down with shingle about 8 months prior. Her comment was that shingles and low B vitamin levels are strongly linked.

We never had any blood cell tests done because John did not have enough white cells and was still transfusion dependent at the time so it was pointless.

Anyways....I just googled on this and found this lab:

http://www.spectracell.com/