Vitamin B12 (Cobalamin)

All the B vitamins together are called the "B vitamin complex." Each type of vitamin B plays different important roles in your body.

Vitamin B12 is needed to make healthy red blood cells and to keep nerves working normally. Low B12 can cause a type of large-cell (macrocytic) anemia, but it can also cause nerve problems such as numbness or tingling in the hands and feet, balance trouble, and memory or mood changes, sometimes even when blood counts still look normal.

You get B vitamins from many foods, including leafy green vegetables, meats and fish, eggs, whole grains, milk, and other dairy products. A lack of vitamin B is rare in the United States, because many foods have added B vitamins. These foods include cereals, breads, and pasta. B12 is mostly found in animal-based foods, so people who eat strict plant-based diets are at higher risk of running low.

Your results will show the amount of each B vitamin that was tested. If your vitamin B levels are normal, but you have symptoms, you may need other tests to diagnose your condition.

If you're lacking in one or more B vitamins, you may need other tests to find out why. A low B12 level can be related to conditions like pernicious anemia, surgery on the stomach (such as a partial or full gastrectomy), trouble absorbing nutrients from food, or certain inherited or biochemical disorders.

Very low B12 levels (roughly under 150 pg/mL) are considered evidence of deficiency. Borderline values (about 150-400 pg/mL) are sometimes hard to interpret. In that range, providers often order extra tests, such as methylmalonic acid (MMA) or homocysteine, which can confirm whether your body is truly running low on B12 at the cell level.

Your provider may recommend taking vitamin B supplements. In certain cases, vitamins may be given by intravenous (IV) treatment.

If you have questions about your results, talk with your provider.