I had taken Metformin(diabetes drug) for years and I guess that it blocked the b-12 absorbsion from my food. My Endo rx Foltanx that is methyl form of b-12 plus folic acid. I will take it as long as I still take Metformin. From your post it sounds like you will have to supplement always also. The common low range number is 400 so if you could get into the 900's I would hope that some symptoms would improve. Good Luck, Ken in Texas.