Prevent anemia
Vitamin B12 helps keep the body’s nerve and blood cells healthy. It also helps prevent pernicious anemia – a type of anemia which can make people feel tired and weak.
Most people get a recommended amount of vitamin B12 from their diet. Some people, however, may need to take a vitamin B12 supplement. These include people with pernicious anemia, vegetarians or vegans who don’t eat enough foods that contain vitamin B12, and older adults whose bodies may not absorb this vitamin as well as they used to.
References
https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
https://pubmed.ncbi.nlm.nih.gov/30074168/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3428233/