If you were already using the B12 when the test was taken, the results will be artificially high. You need to stop all B12 about a week before any testing, to get a more reasonable result.

If you use the B12 under the tongue, do so on an empty stomach.
Most is dissolved in the saliva and swallowed, so it needs to be on an empty stomach to get best absorption, in the small intestine.

Methylcobalamin is the best form to use, and many people have a DNA mutation in methylation (MTHFR), and cannot activate cyanocobalamin form.

And yes, the Nexium could be a problem, including the following other nutrients:
Folate
calcium
magnesium
iron
zinc
B12
and possibly other trace minerals like copper, chromium, etc.