How much b12 is needed to supplement a vegan diet?

2.4 mcg: Assuming you are not otherwise B12 deficient, you need at least 2.4 mcg per day (more if pregnant). You can get this from pretty much any supplement containing b12. You should, however, get your blood tested to make sure you're not already deficient. If so, you can "catch up" before going on maintenance supplementation. Good job on going vegan. Now just make sure you take a B12 supplement.

First determine need: You do not need to supplement, unless a need is diagnosed. Some physicians will test for you , but a naturopathic physician may be more in tune with vegan needs.