There are several sources now. This one from AAFP is over ten years old now:

http://www.aafp.org/afp/2003/0301/p979.html

Dr. C Snow MD started the US informational updates on B12 with his JAMA paper. This post has the link and quotes from it.

http://neurotalk.psychcentral.com/post698522-70.html

Japan has been a leader in B12 research. This is because in the 1970's a drug there caused enormous damage and death by blocking B12 in the body. It was called Vioform (now called clioquinol)...and lead to blindness and spinal damage, and death by the thousands. So Japan has been a leader and very aggressive in keeping B12 levels higher than our old outdated US range which still has not been changed sadly.

http://chriskresser.com/b12-deficien...s-consequences

You can Google Japan clioquinol damage, or Japan B12 treatments, etc.

What is also important is the type of B12 to use. Now we know that genetically people do not convert cyano synthetic form still commonly used by doctors, to the active methyl form. So with the methylcobalamin oral costing pennies a day, it is really the one to use today. You have to take it on an empty stomach to get adequate absorption however.

This is my B12 thread:
http://neurotalk.psychcentral.com/thread85103.html

There is much information on that thread, and discussion.

If you are one of the 10-30% of people with the MTHFR mutation, the cyano will not work for you (nor will folic acid).
You will need both methylcobalamin and methylfolate for replacing those nutrients.

More here:
http://mthfr.net/

The genetic information is still not being picked up by doctors. But you can request the DNA test and get it from your doctor, or even yourself from the net (no doctor order required).

The sooner you address this, the better for you. Good luck.

If you could send me your doctor's name via PM, I am curious if I know of him/her.... I live in your area. But I have been retired for over 4 yrs now, and losing touch with most doctors.

P.S.... sometimes one reported result in the common CBC testing will show a minor trend to be high normal or out of range...this is the MCV value. It will hint at a possible low B12
trend but most doctors are trained to IGNORE it.