All of the B12s are still sublingual...but really they dissolve in your saliva and you swallow it anyway. Very little goes thru the mouth membranes. B12 is such a huge molecule and all.

But you DO have to take it orally or subling if you choose, on an empty stomach. Food will absorb it's tiny microgram amount and prevent the passive absorption in the small intestine.

If you have intact intrinsic factor (and most people who are low do not), then that is easier for absorption.

The research on microgram amounts of drugs was done on levothyroxine and was shown that food ruined it's absorption. Then digoxin was added to the list. So that now if you get these on RX, there will be a warning sticker. For some odd reason no one has understood or picked up on it yet, for microgram amounts of B12... not even the supplement manufacturers!
But I know about this, and know it is crucial to get good absorption orally. Just don't choose a "timed release" product as that is USELESS.