--be sure to have them titer your anti-gliadin IgG and IgA (the former is the most sensitive, but least specific test to see if you are making antibodies to gluten, and is often associated with non-celiac gluten sensitivity); the anti-transglutaminase IgA and IgG (the first being the most closely associated with celiac that would have progressed to the point of degeneration of intestinal villi); and total IgA (some people have deficiencies in this and it skews the result of the other tests).

There are some more advanced tests in the pipeline that are supposed to be more specific, but I've yet to see them appear at standard labs. The Gluten File discusses this, and lots of other things--it is an excellent resource:

http://sites.google.com/site/jccglutenfree/

Many of us develop absorption problems as we age--you may not have any gluten problems and may be suffering from lack of intrinsic factor to break B12 out of food, and that should be investigated as well.