I've learned a lot about B12 deficiency during the past few months so I thought I'd just add a tidbit here that I came across....info on this subject is hard to find.

Your body is very efficient at storing B12, as long as there is no medical issue preventing from doing so. The amount of B12 needed each day is actually quite low, and if you stopped getting any it would take somewhere around 4 years for your body to run out. That's for someone with normal levels and no medical interference.

One year ago I became extremely ill after months of going downhill. I won't get into the hell I entered, but it wasn't until it had reached a very dangerous stage that it was finally discovered that my B12 level was 96. Yes, 96. At the same time, it was also discovered that my iron level was just as dangerously low and I also had a vitamin D deficiency. Yep, it was a pretty ugly situation. I'm much better now, but still in recovery.