My B-12 hit rock bottom after my knee surgery. I took B-12 shots 2x a month for several months, then once a month for a year, and now take 2000 mcg's orally every day. I knew something wasn't quite right within a few weeks after surgery; I felt absolutely drained, a bit jittery and nervous inside (antsy), wasn't sleeping well, and had to really push / force myself through my physical therapy sessions. Luckily, I had a medical appointment already scheduled, so my doctor ordered lab work, which showed my extremely low B-12 level. Within 1-2 days after the first shot, I felt calmer, was sleeping much better, and didn't feel so exhausted after my physical therapy sessions. After the second and third shots, I really began to feel more energetic, and more like me.
The B-12 shots will be very beneficial to you, and I am confident you will start to feel so much better in a very short amount of time. Best wishes to you!