remember only yeast labeled 'Red Star Yeast T6635+' is fortified with B12, other types have NO B12. sometimes its labeled as 'vegetarian support' yeast, but it should have the numbers 6635 somewhere on the label. if not it most likely has no B12.
i dont really see the difference between using this or taking a B12 supplement however. the yeast only has B12 because it was put in there by humans during the fermentation phase.