LabCorp Test

Vitamin B12 Blood Test

Quick Overview

Measures the amount of vitamin B12 in the blood and helps diagnose the cause of macrocytic anemia.

Test #001503


Availability: In stock

Also Known As Cobalamin; Cyanocobalamin; B12; Cobalamin, True
Preparation Fasting for 12 hours required. Stop biotin consumption at least 72 hours prior to the collection. Must draw before Schilling test, transfusions or B12 therapy is started.
Test Results 1-2 days. May take longer based on weather, holiday or lab delays.

The Vitamin B12 Blood Test from Walk-In Lab helps diagnose macrocytic anemia and neuropathy, and evaluates and monitors treatment for Vitamin B12 deficiency.

This test is used to detect B12 deficiency as in pernicious anemia; diagnose folic acid deficiency; evaluate hypersegmentation of granulocyte nuclei; follow up MCV >100; diagnose macrocytic anemia; diagnose megaloblastic anemia; evaluate alcoholism, prenatal care; evaluate malabsorption, neurological disorders, or the elevation of B12 as seen in liver cell damage or myeloid leukemia

Vitamin B12 is necessary for the formation of normal red blood cells, nerve function, and tissue and cellular repair. It is not produced in the human body, but rather ingested when consuming foods such as red meat, poultry, fish, milk, eggs and fortified products such as certain breakfast cereals and breads. Deficiencies can be caused by malabsorption (when a disease or other condition interferes with the absorption process) or insufficient dietary intake, although this is unusual in the United States due to the number of food items that have added B12. Vegans and those who do not consume animal products may be more prone to deficiencies.

A deficiency can lead to macrocytic anemia (when the body produces fewer, but larger red blood cells) and neuropathy (nerve damage causing tingling and numbness in the hands and feet).

Symptoms that suggest a Vitamin B12 deficiency include:

  • dizziness
  • weakness
  • fatigue
  • sore mouth or tongue

Common causes for Vitamin B12 deficiency include:

  • malnutrition
  • liver disease
  • alcoholism
  • malabsorption disorders such as Celiac Disease, Cystic Fibrosis and Inflammatory Bowel Disease.
  • Above normal heat production (for example, with hyperthyroidism)
  • Pregnancy

An increased vitamin B12 level is uncommon. Usually, excess vitamin B12 is removed in the urine.

Conditions that can increase B12 level include:

  • Liver disease (such as cirrhosis or hepatitis)
  • Myeloproliferative disorders (for example, polycythemia vera and chronic myelogenous leukemia)

A Vitamin B12 Blood Test may be ordered if a CBC with Differential detects large red blood cells.  Vitamin B12 is usually measured at the same time as a folic acid test.

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