--take the B12 far apart from food--at least an hour before any food, or two hours after--so that if you are megadosing (taking at least 1000mcg at a time) you have the chance for maximum passive absorption of the cobalamin without anything for it to bind to it and interfere with it.

Even the so-called subligual tablets that one sucks on for a time tend not to be absorbed through the mouth, but tend to be swallowed and later absorbed in the small intestine. This is because the cobalamin molecule is the largest one normally used by the body for essential processes and it needs to be chemically transformed for usability (without getting too technical about this, it needs to be methylated, which is why many of us prefer the methylcobalamin form outright--fewer chemical hoops to jump through); this is also why it is easy to interfere with its absorption if it is consumed with other foodstuffs.

Mrs. D talks about the outmoded ranges that still appear on laboratory tests for serum B12--I think that anyone on a non-vegetarian diet should be thinking that the lowest acceptable range is 500 or even 550, as it is in Japan, not the 400 or so Mrs, D mentions and certainly not the 180 or 200 one sees on a lot of lab reports. People in those low ranges are almost certainly deficient and symptomatic; even people in the 400-500's often are. People with normal body chemistry without absorption problems who eat some animal products probably should be at least in the 600's, and many are higher. Dr. Snow's medical texts and Family Practice guidelines have noted some people have been symptomatic even in those ranges.