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Vitamin B12 Blood Test

Last updated June 2, 2019

Approved by: Krish Tangella MD, MBA, FCAP


Foods, such as cereals, are supplemented with vitamin B12. This is one of the reasons that vitamin B12 deficiency is rare in the United States, even among vegetarians. Vitamin B12 gummies are also a delicious and easy way for an individual to obtain vitamin B12.

What are the other Names for this Test? (Equivalent Terms)

  • Cobalamin Blood Test
  • Cyanocobalamin Blood Test
  • Vitamin B12 Blood Test

What is Vitamin B12 Blood Test? (Background Information)

  • Vitamin B12 (or B12), also called cobalamin, is part of the B complex of vitamins. It is important for red blood cell (RBC) production, nervous system health, and tissue repair. Vitamins, such as vitamin B12, are essential because certain enzymes require them to perform necessary chemical reactions
  • Vitamin B12 is obtained through the diet. Foods rich in vitamin B12 include animal products such as meat, eggs, and milk. Consequently, strict vegetarians must obtain adequate supplies of vitamin B12 through other sources. Also, individuals who are pregnant, in early childhood, or who have cancer, may require increased amounts of vitamin B12
  • One of the most important uses for vitamin B12 is red blood cell production, or erythropoiesis. This occurs in the bone marrow. Vitamin B12 deficiency may lead to the production of fewer but larger red blood cells, a type of anemia
  • Additionally, vitamin B12 deficiency could cause developmental defects in a growing fetus. This is because vitamin B12 is necessary for cell division, which occurs during development at a rapid rate
  • Vitamin B12 is contained mostly in the fluid portion of blood, called the plasma. Plasma comprises one-half to two-thirds of the volume of blood; the rest is cells, such as RBCs
  • Vitamin B12 requires a protein called intrinsic factor to be taken in. Intrinsic factor is made by special cells in the stomach called parietal cells. Once the intrinsic factor binds to vitamin B12, the two are taken into blood by a carrier protein called transcobalamin
  • Individuals who suffer from malabsorptive disorders, such as celiac disease and cystic fibrosis, may have difficulties absorbing vitamin B12, even though they eat foods rich in vitamin B12
  • The Vitamin B12 Blood Test measures the level of vitamin B12 in blood. It is used to determine if a deficiency is present, which could indicate other conditions such as malabsorptive disorders or malnutrition

What are the Clinical Indications for performing the Vitamin B12 Blood Test?

Following are the clinical indications for performing the Vitamin B12 Blood Test:

  • Differentiating different types of anemias
  • Screening for malnutrition and malabsorptive disorders
  • Altered mental status, behavioral change
  • Diarrhea
  • Dizziness
  • Fatigue, muscle weakness
  • Loss of appetite
  • Pale appearance
  • Shortness of breath, irregular heartbeat
  • Sore tongue and mouth
  • Tingling in the extremities

How is the Specimen Collected for Vitamin B12 Blood Test?

Following is the specimen collection process for Vitamin B12 Blood Test:

Sample required: Blood

Process of obtaining blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Vitamin B12 Blood Test Result?

The significance of the Vitamin B12 Blood Test result is explained:

Increased vitamin B12 levels may indicate:

  • Chronic granulocytic leukemia
  • Chronic kidney failure
  • Chronic obstructive pulmonary disease (COPD)
  • Diabetes
  • Leukocytosis
  • Liver cell damage, such as with hepatitis and cirrhosis
  • Polycythemia vera
  • Severe congestive heart failure
  • Carcinoma

Decreased vitamin B12 levels may indicate:

  • Liver disease
  • Gastric cancer
  • Celiac disease
  • Inflammatory bowel disease
  • Cystic fibrosis
  • Crohn’s disease
  • Bacterial or parasitic infection
  • Pancreatic insufficiency
  • Hypochlorhydria
  • Pernicious anemia

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Foods, such as cereals, are supplemented with vitamin B12. This is one of the reasons that vitamin B12 deficiency is rare in the United States, even among vegetarians
  • The Vitamin B12 Blood Test is rarely ordered in the US. The homocysteine and methylmalonic acid (MMA) tests are often ordered alongside the vitamin B12 test. Both homocysteine and MMA would be elevated in the case of a vitamin B12 deficiency
  • Vitamin B12 is unusual because it contains an atom of cobalt. Cobalt is rarely found in the body
  • Certain factors influence the results of this test and these include diet, alcohol consumption, body composition, and smoking

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

  • A methylmalonic acid (MMA) blood test is a test that assesses the levels of MMA in blood. It is used to indirectly detect vitamin B12 deficiency

The following article link will help you understand methylmalonic acid (MMA) blood test:


The homocysteine blood test measures homocysteine levels in blood. It is used to detect vitamin B deficiency or genetic disorders affecting homocysteine metabolism

The following article link will help you understand homocysteine blood test:


Please visit our Laboratory Procedures Center for more physician-approved health information:


References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: July 10, 2015
Last updated: June 2, 2019