There are studies showing passive absorption takes place in
the intestines, for PA patients without intrinsic factor.

Here is the link of a table used to measure blood levels:

http://www.ncbi.nlm.nih.gov/pmc/arti...able/T1/#TF1-4

The column to the right of the table, shows PA levels.
at 1000 mcg oral the absorption is almost the same as for non-PA patients.

Methycobalamin is the preferred type to use, since some people cannot convert cyano form (which is inactive and synthetic).

Using oral forms of B12 requires no food be present. If food is present absorption will be hindered and much lower. So empty stomach and nothing for an hour after, is best.

There are some medical sites now, that encourage doctors to use
oral treatments now. These of course are best done every day...and now can cost just pennies a dose. The one we use now from Costco cost us 6 cents a dose.