The first step is rate-limiting and subject to feedback inhibition by glutathione itself, holding intracellular concentrations in the low millimolar range, typically 1 to 8 mM (Griffith, Free Radical Biology and Medicine, 1999
Doctors have traditionally given injections of B 12 to patients with pernicious anemia
Velzeboer R, Malas A, Boerkoel P, et al
That last property is part of why it gets discussed for soft-tissue injuries and gut conditions alike
I have been using the MIC, B12, L-Carnatine Injection Homesite for going on 3 weeks
The container must be rigid, leak-resistant, puncture-resistant, with a tight screw cap, and clearly labeled (e.g., SHARPS DO NOT RECYCLE)