I'm in the U.S., was doing a cyanocobalamin injection once a month, but felt I needed it more, so my husband was trained to inject. I find that I have "bouts" of fatigue, and have tracked all sorts of dietary factors, exercise, sleep, alcohol use, mood, etc for months on end, and can find no correlation between my fatigue and any lifestyle factors.
But I also can't find any correlation to my B12 shots. Sometimes I can go 5 weeks between shots; other times, I get one and don't feel any better and want another one in only a couple of days.
My pharmacist told me this week that from now on they will only be supplying the 1-dose vials; he said the 10-dose vials are no good after 28 days. So I thought that might be the explanation...that I was getting less response as the serum got older...but looking at my ridiculously detailed log, that doesn't explain it either.
I know some people do fine on a month between doses, others need it more frequently...but does anyone find that the need for doses is wildly inconsistent?