Vitamin B12 is concentrated in meat but in many cases animals get B12 supplements because modern farming reduces animal uptake of soil bacteria.

People often get B12 from meat, fish and dairy products, from fortified cereals and from supplements. B12 supplements are recommended for vegetarians and vegans, pregnant and breastfeeding women, people that have low absorption due to digestive conditions, people on certain medications (e.g. metformin) and sometimes elderly people.