Cyanocobalamin is in the B12 shot.

Are you sure about that every other day for 3 months?

That is extreme. Usually they are given often say, once a day for 7 days or every other day for 2 weeks, then once a week, or twice a month. Best to have blood work done in between shots to see if they are working. So the frequency is only in the beginning, and does not continue over time.

Cyanocobalamin is B12+cyanide ...it is a tiny amount but given so often, it might be hard on some people. Then there are those who cannot activate this synthetic form, and so it doesn't work right.

Methylcobalamin oral is much better IMO. OTC 5mg a day on an empty stomach, and no cyanide.

I'd clarify why the B12 so often by injection. There is another form for injection called hydroxocobalamin that does not have the cyanide portion. Methyl B12 is available in shots, but typically is made by compounding pharmacies and doesn't come in a multi use vial for self administration.