That’s very helpful, LULZmouse.
Lots of info there too. Yeah, the only supplement I could find around here (that was USP verified) was for 500 mcg. So I was looking up what kind of dose this might correspond to in practice (being that it’s a megadose on paper). The article says about 9.7 mcg would be absorbed (and the rest is water soluble), so every other day would be okay. They say skin rashes are the most common side effect of a high dose, which is rare at that, so it might be easy to detect (sooner than later), unlike a deficiency. Vegans are among the least likely to absorb too much, as well, based on the interplay of other nutrients in the diet with cobalamin. Likewise, a deficiency of B12 can result in more plentiful nutrients in the diet not being absorbed. Their conclusion states that underestimating the correct supplementation of cobalamin can nullify the health benefits of a vegan or vegetarian diet.
Does vitamin C prevent vitamin B12 absorption? I found conflicting information on the net.