You can get recommended amounts of vitamin B12 by eating a variety of foods including the following:
Beef liver and clams, which are the best sources of vitamin B12.Fish, meat, poultry, eggs, milk, and other dairy products, which also contain vitamin B12.Some breakfast cereals, nutritional yeasts and other food products that are fortified with vitamin B12.
According to the NIH, vitamin B12 is also found in almost all multivitamins.
“Dietary supplements that contain only vitamin B12, or vitamin B12 with nutrients such as folic acid and other B vitamins, are also available,” explains the NIH.
It adds: “Vitamin B12 is also available in sublingual forms (which are dissolved under the tongue).”