of all the B vitamins, the injected form of B1 has the potential for anaphylactic shock--I have severe allergies, and have had anaphylactic shock with other things, so an not willing to go for the shots (and am sure my Dr would also say no).
I use B1 capsules, and keep them under my tongue, like a lozenge. Not the best taste and sensation, but B1 is very hard to absorb.
I am going to try Benfotiamine, a synthetic form of B1 that is absorbed better, and apparently works better (and of course, is more expensive
And yes, don't use Cyanocobalamin injection for several reasons:
!)the methyl form is the form our body makes (from the cyano) that is so beneficial to nerves
and 2) the injectible cyanocobalamin uses aluminum in its production--check the insert, it is listed as one of ingredients.
My Dr gives me script for needles and for the methyl B12--I inject myself (very easy, you get used to it).
Dr Klenner was working in the 1940's--they did not produce methyl form then, this is very recent. Likewise, Benfotiamine very recent to US.