Vitamin B12 test

The vitamin B12 test is a blood test used to evaluate the concentration of this essential vitamin in the body. Vitamin B12 is vital for DNA synthesis, the maturation of red blood cells, proper nervous system function, and energy metabolism. Deficiency typically manifests as macrocytic (megaloblastic) anemia and may also lead to neurological disorders.

The test is especially useful when elevated MCV and MCH values are observed, when symptoms such as weakness and thrombocytopenia are present, when characteristic morphological changes in granulocytes are detected, or when megaloblasts are found in bone marrow samples.

Vitamin B12 is no longer synthesized in the human body, so deficiency can result from various causes, such as:

• Gastric diseases (atrophic gastritis, gastric cancer, gastric surgery),
• Intestinal disorders (malabsorption, Crohn’s disease, diverticulosis, helminthic infections),
• Bone marrow diseases (idiopathic megaloblastic anemia),
• Medication use (barbiturates, oral contraceptives, metformin, cytotoxic drugs),
• Alcoholism, liver or pancreatic diseases,
• Rarely – disorders of transport proteins or cobalt metabolism.

Vitamin B12 deficiency can also be masked by or resemble other conditions, such as leukemia or pre-leukemic states.

Test Principle:

Vitamin B12 is measured from venous blood serum using an immunochemical assay. Results are reported in pmol/L or pg/mL. If the results are inconclusive, the level of holo-transcobalamin (the active form of B12) may be assessed.

Recommendations:

• The test is recommended when macrocytic or megaloblastic anemia is suspected.
• It is useful for evaluating neurological symptoms such as paresthesia, impaired vibration sensation, and memory decline.
• It is indicated for patients with intestinal, gastric, liver, or pancreatic diseases, as well as for those taking medications that may reduce B12 absorption.
• The test is also performed for pregnant women, vegans, the elderly, and in cases of unexplained fatigue or abnormal blood test results.
• It is recommended to fast for at least 8 hours before the test and to avoid taking B12 supplements for 1–2 days prior.