Understanding Vitamin B12 Blood Tests: Purpose, Symptoms & Interpretation

A B12 lab, also called a vitamin B12 blood test, is used to measure the amount of B12 in an individual's blood stream. Vitamin B12 plays a key role in maintaining a properly functioning nervous system and is a necessary component in the formation of blood cells.

Symptoms

• The B12 lab is performed when a doctor suspects a vitamin B12 deficiency. Symptoms of the deficiency include numbness and tingling in the arms and legs, weakness, headaches, fatigue, paleness, loss of balance and dementia.

Function

• A phlebotomist draws blood from a vein typically located in the arm or hand.

Standards

• Normal values for a B12 lab are 200 to 900 picograms/milliliter (pg/ml). Results less than 200 pg/ml indicate a vitamin B12 deficiency.

Significance

• B12 deficiency could be a sign of a megaloblastic anemia such as pernicious anemia. Other conditions include a restrictive diet, Celiac disease, Crohn's disease and pregnancy.