I think I may have problems with cyano and methyl B12 too. Either it just doesn't agree with me at all, or it's too much for my body to handle, or it causes over-methylation or something. But I seem to not be able to do it. It causes very high anxiety and stress.
However, I do seem to tolerate B12 injections (hydroxocobalamin) well, up to the point of 1000mcg per injection, with "only" low potassium symptoms. By contrast I can't even take 50mcg of cyano or methyl B12 in tablet form because of the aforementioned reactions. Right now I'm on a very low dose of 10mcg of cyano B12 but I think I might give that up completely and go with hydroxy B12 instead.
However, I've only taken 1000mcg hydroxocobalamin as injections as frequently as once per week, so I'm not sure yet how I'd go in having that amount every day, or even 500mcg each day (or every second day etc.)
I'm going to order hydroxocobalamin as lozenges online soon, so that way instead of going to the doctors and needing an injection, I can control the dose at home and increase it to more than 1000mcg per month/two weeks, however frequent the dr thinks I should have it. Doctors aren't keen on an injection every day because they undervalue B12. And I'm not comfortable with injecting it myself so hydroxy B12 lozenges are the way to go, I think.
If you want to follow my progress with hydroxy B12 and doses you can go to the link in my signature.