how does the b12 injection work Shots at Home: How, Where & Often to Inject Yourself B12 Shots vs. IV Infusions:
Description
Specifically, 5-amino-1MQ and 7-amino-1MQ exhibited high passive and active transport across membrane, with no detectable efflux observed in the Caco-2 cell assay
One of the treatments given by veterinarians is injections of vitamin B12, also known as cobalamin or cyanocobalamin

Nothing here implies weight-loss efficacy in people
Development & validation of LC-MS/MS assay for 5-amino-1-methyl quinolinium in rat plasma: Application to pharmacokinetic and oral bioavailability studies (in Eng)