Not yet investigated
What we have so far
It rises when B12 runs short, and it rises before serum B12 falls — which is why a normal B12 does not settle the question.
This star is on the map because the show intends to take the question apart properly — the trials, how it is actually tested, whether the thing sold is the thing studied. That work is not done yet, and nothing here should be read as a conclusion. When the investigation is published it will appear on this page.