Welcome to NeuroTalk:

I am on vacation with only an iPhone so
This will be brief.

Yes oral works and there are no studies
Showing sublingual is any better.
One study did measure blood levels after
various oral doses. 1000mcg yielded
13 micrograms absorbed and that is
3 times the RDA from food

But you have to take it on an empty stomach
(No food present).

It is best to use methyl cobalamin form
Which is the active type, as some cannot
Convert Cyano type properly.

Our Peripheral Neuropathy forum has a
long informational thread in the sticky section
With medical links to good sites with
More documented information.

If you begin with 5 mg of methylb12
You can test at over 1000 within 3
Months. Once you reach your goal oral is
enough to maintain. This works out to
pennies a day.