glutathione for pain Intramuscular (IM) Injections Harnessing the Power of Glutathione:

Octreotide (MW 1019 Da) offered the advantage of a relatively small increase in stability in intestinal fluid afforded by a macrocycle backbone, two D-amino acids, and a modified C terminus, 11 whereas semaglutide remained unstable in the GI tract despite being stable in plasma due to affinity of its fatty acid chains for albumin

283 , C142C147 (2002)

Perineural invasion in cancer: a review of the literature

So, you measure a higher B12, but part of that B12 is inactive, so useless Oral B12 supplementation, even in the form of a multivitamin preparation, may result in serum B12 concentrations just within the normal range without abolishing symptoms