The latter may be caused by intestinal disorders, infections, bariatric surgery, or pharmacological interference, including histamine H2 receptor antagonists and metformin
[DOI] [PubMed] [Google Scholar] Riley 2011 Riley RD, Higgins JP, Deeks JJ
But unless you have a vitamin B12 deficiency, vitamin B12 injections aren't likely to give you an energy boost." Ironically, the National Institutes of Health says that symptoms of B12 deficiency include loss of appetite and weight loss
As well, the number of intramuscular injections a patient needed to receive to be included in the cohort varied from 6 or more injections to 4 or more injections within 1 year
doi: 10.1016/S0140-6736(05)79821-4
10.1016/j.amjmed.2003.09.046 46 RuckerR