how often are b12 injections needed Do You Need a Prescription for Injections? How Can Vitamin B12 Shots

Mammalian herbivores, including nonhuman primates like gorillas, and our fellow great apes, get all the B12 they need by practicing coprophagy, the eating of feces, but my preference would be to take B12 supplements

Advances in Food and Nutrition Research

Individuals with Vitamin B12 Deficiency: Through blood testing, we can confirm a B12 deficiency and provide immediate treatment with injections if necessary

PMID 28032115

Some patients, particularly those with neurological involvement, may benefit from more frequent dosing (every 2 months rather than 3 months), but this should be medically supervised rather than self-adjusted