What is good for pernicious anemia?
The best bioavailable source of B12 in it's natural source is liver. Either consume some grass fed with onions or in a pill. There are 2 other reasons why B12 might not work. (1) The stomach might be too alkaline in which case some betaine hydrochloride would help or (2) the person is lacking something called the intrinsic factor, which allow B12 to be absorb. I like the Standard Process product called Cataplex B12 for that.