I too suffer from PA and have injections every 12 weeks. However, I don't really notice the fact that I am low after 10 or 11 weeks so I can only think that it is the sublingual methylcobalamin I take that helps? I know that those of us with PA cannot absorb much through the stomach but with the sublingual I believe part of it is absorbed through the skin (you keep it under your tongue for 30 seconds before swallowing) so that may help?? You can buy them on Amazon. However, regarding the question about whether your body will store B12 so you can overdose as it were - I remember reading that when there was the discussion concerning Bovine TB, one of the solutions considered was giving badgers huge doses of B12. I am not aware of why that would protect against TB but do remember that the paper concerned stated that B12 is 'pee'd' away if you have too much?? It might be worth reading up on B12. I am only given a blood test once a year (and then only if I ask) so stop taking the B12 sublingual a week or so before in case, as you say, they take away my injections.