who gives b12 injections at Home - Safety Guide for Self-Administration Compounded Cyanocobalamin (Vitamin B12) Injection

That longer action is part of why maintenance injections can be spaced months apart rather than weeks

Proton-pump inhibitors (e.g., omeprazole, esomeprazole, and lansoprazole), used to treat Zollinger-Ellison syndrome and gastroesophageal reflux disease (GERD), markedly decrease stomach acid secretion required for the release of vitamin B 12 from food but not from supplements

Phentermine Phentermine is a prescription appetite suppressant that supports weight loss by reducing hunger and increasing fullness

This is a link to the American Familly Physicians page on treating people with B12 absorption problems

Mayo Clinic Proceedings: Innovations, Quality & Outcomes , vol