Vitamin B12

A vitamin B12 test measures the amount of vitamin B12 in the blood. The body needs this B vitamin to make blood cells and to maintain a healthy nervous system.

Vitamin B12 is found in animal products such as meat, shellfish, milk, cheese, and eggs. Most people who eat animal products are not likely to develop vitamin B12 deficiency anemia. unless their bodies cannot absorb it from food. Vitamin B12 is stored in the liver for a year or more, which reduces a person's risk of anemia. Strict vegetarians (vegans) who do not eat animal products, and babies of mothers who are strict vegetarians are at increased risk for developing anemia and should take a supplement containing vitamin B12.

Vitamin B12 is usually measured at the same time as a folic acid test, because a lack of either one can lead to a form of anemia called megaloblastic anemia. Lack of vitamin B12 also affects the nervous system.