Hello @azgama, Welcome to Mayo Clinic Connect. Here is some information from Mayo Clinic on vitamin B-12 that may help -- https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663. Also the National Institutes of Health Office of Dietary Supplements has a Factsheet for Consumers here: https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/.

Can I ask what made you decide to find out more about Vitamin B-12?