Obviously your doctor does not know much about B12.

Do you know (and does he know) that the ranges used for testing are based on statistics? That is, people are tested in a group and the ranges are taken from that. (they are considered normal "healthy" people--which they may not be.)
There are no studies showing that higher B12 levels are harmful to anyone. Normal people who do not take supplements are not going to show high levels either.
Many people who see benefits from B12 supplements have readings of 2000 or higher.

There are no studies showing an upper limit of toxicity for B12.

Is this what you are taking?
http://www.iherb.com/ProductDetails.aspx?c=1&pid=110
If so it doesn't have much in it to worry about. The B12 level in it is only 100mcg.

In other countries (Japan for example) anyone lower than 500 is treated with supplements. In fact your levels are rather low considering you are supplementing..
http://www.labtestsonline.org/unders...n_b12/faq.html

http://www.labtestsonline.org/unders..._b12/test.html

I'd suggest you do some Googling, and print out stuff for your doctor to read. He needs some updating.