The short answer to the last question is "Yes, unless they are knowledgeable." At the Scripps Center for Complementary Medicine, where my cardio is, the medical staff is very knowledgeable about nutrition.

I believe that the B-12 test tops out at 2000, so no, you cannot get a reading higher. I concur with others here that B-12 is harmless in amounts we are likely to take. In Japan injections of 30 mg./week (that's 30,000 mcg.!) were an effective and safe clinical treatment for PN. I don't know if they still do that in Japan, but the point is that's more per week than you take in many months.

Your liver stores between 2,000 and 5,000 mcg. of B-12 and doles it out as your body needs it, under 5 mcg. per day. Now that your stores are built up, 1 or 2 mg.(1,000-2,000 mcg.) per week, taken all at once (assuming you have no intrinsic factor to help absorption) should keep the level up to maximum.