Hi all, I have been on sublingual hydroxy b12 for the last 4 months (following a b12 deficiency diagnosis)... slowly increased it up to 2000mcg a day. My serum b12 was tested several times and gradually increased from 150's up to upper 400's on my way up to the 2000mcg. I've continued to take this daily dosage for the past 2 months and just had a recheck - the level seems to be at a plateau, as I have only gone up from 479 o 498 in these two months. What might be some causes for this? Thanks!