Used to be even more surprising for me - I didn't have to take supp. Some of us actually do have more B12 resources. Plus you can go vegan for 4 years without supplementing. But it's B12 in the dairy that will actually be the main reason. I was never that strictly vegan. Probably strictest now, and to be on the safe side I do sometimes buy = eat or drink some when expired/overdue (hate the thought of that going wasted).
Yeah, my wife's been giving me 5mg methylcobalamin jabs s.c. and cos those boosters made my levels rocket I was only needing 1 every 3 months. Didn't make a difference (like D3+K2-MK7), but makes sure it's not that. Be ordering again soon from a compounding pharmacy, maybe this time 1mg, alternating the 3 good types hydroxo-, methyl- and adenosyl-cobalamin, because they all have certain advantages.
If my wife wouldn't do the jabs, I think I've got the balls to do it on myself, at least now I've seen and felt how she does it. But it's good for her to have something she can do for me. My docs wouldn't, I've also got some high dose L-carnitine and vitamin C to be injected i.v., but no one I know has the spunk to do that, so it's wasting away. Maybe I'll drink it some day, if I don't get some nurse to have pity on me.