--is much too low, no matter what the general lab norms say. (Although, the more updated lab norms will often have 400 or even 500 as the lower limit of normal.)

You should be supplementing immediately--dosing with anywhere from 1000 to 5000 mcg (1mg-5mg) of B12 daily, preferably the methylcobalamin formulation rather than the cyanocobalamin type (in case you may have some deficiencies in methylation chemistry, which are actually quite common; the methyl form will bypass that pathway and be absorbed more readily). This way, even if you have pernicious anemia (not really an anemia, but a dysfunction of stomach parietal cells that disable the ability of B12 from being broken out and absorbed), or another absorption problem, the large dose will enable enough passive absorption to hopefully rebuild stores. (The actual daily requirement of B12 is usually set at around 3-10 mcg--passive 1-2% absorption should enable you to rebuild stores, injections notwithstanding.)

You should also look at our B12 thread:

STICKY - The Vitamin B12 Thread: