It seems from reading posts on this site anb my experience that most of these dr's don't seem to know much about the b12 def. As MrsD says, they are learning new things about it though.
I actually went to a Hemotolgist who told me that 200 was a normal level... when I ask him "then why am I feeling like crap?" he shrugged his shoulders... "I don't know!" NICE right. Anyway I found a great dr who is very educated and open minded about this condition. He said that you need to be above 500 to be close to normal. 2000 is actually normal. He recomended one 1mg shot a month for 6 months while also taking my sublingule suppliments. Thats me though, a lot of people on this site have been taking the 5000mcg a day like MrsD said and it's working for them.
For me, the suppliments alone weren't working fast enough, maybe I'm impatient or maybe my body isn't absorbing it... that I won't know until after I get my testing done on my very screwed up stomach. Either way, since I started on these shots, I have been feeling a lot better. But I am still taking 3000 mcg a day.
Good luck... if you are not getting what you need from your dr, find a new dr. You can help yourself, but why have a dr if they can't help you?