do b12 tablets work as well as injections Are Vitamin Shots Right for You? Oral vitamin B12 versus intramuscular

But a huge number of meat eaters are also deficient and likely dont know it B12 is absorbed through the stomach, and our ability to assimilate it through the stomach wall decreases with age, as well as due to any stomach issues like IBS, Crohns, and Celiac Disease, and medications that impact the stomach like metformin, antacids, PPIs, and ibuprofen

doi:10.1007/s11695-017-3102-y

Deficiency can occur in certain populations, including older adults, vegans, individuals with pernicious anaemia, those with malabsorption disorders such as Crohn's disease or coeliac disease, people who have had bariatric surgery or gastrectomy, and those on long-term medication such as metformin or acid-suppressing drugs

Additionally, it is often not enough to just eat more iron-rich foods or supplement with iron