I just got a B12 shot this morning, actually. I got one last month too. It helped for about 2 weeks, then I started feeling exhausted again. I'm hoping it lasts longer this time. I also have sublingual B12 tablets I take every day, but the doctor says they won't really help if the problem is how my body absorbs it (as opposed to me not getting enough). My mom and sister needed B12 shots for a while, so it's probably something that runs in the family, unfortunately.