VITAMIN B12
What it isOne of the two active coenzyme forms of vitamin B12, cofactor for methylmalonyl-CoA mutase.
Why this oneIts deficiency is what raises methylmalonic acid, the most specific marker of B12 deficiency.
What limits itIt explains why methylmalonic acid, not B12 level alone, confirms functional deficiency.
NO BOXED WARNINGS
Principal riskEndogenous or dietary; no boxed warning applies
