Yes, B12 has to be absorbed. If it is not hooked up to intrinsic factor, is has to be given in high dose and passively absorbed instead. That is why you should take it on an empty stomach, so food does not sponge it up and reduce this absorption.

Malabsorption can occur if you have Crohn's disease, removed intestines, or Celiac.

The only substance that I know that enhances absorption is Bioperine, and that is still pretty unresearched.

L-Glutamine is one thing the GI tract needs to stay healthy. If you are very low in this amino acid things suffer. It is recommended for Celiacs too. Having enough EFAs (Omega-3s) in the diet or thru supplements also enhance the lining of the GI tract to stay healthy. If you have infections or Candida of the GI tract you may have trouble.
This is one example:
http://www.thegreenpharmacy.com/Cata...er-360-gms.htm
There is a downside to excess glutamine--- it can lead to too much glutamate in the body.
http://mental-health.emedtv.com/glut...e-effects.html
Most high end whey powders have extra glutamine added.
That is one of the better ways to get it, along with the other amino acids in the whey.

One way you can test yourself to see if you are absorbing things, is to take a B-50 complex and time its appearance in your urine. High B intake changes the urine's color and odor. Most people excrete B's within 4 hrs or so. You can also take an OTC drug phenazopyridine, sold for bladder pain in most feminine hygiene departments. 99mg and time when it appears in your urine. AZO standard is one brand, but there are many.