Vitamin B12 (cobalamin)

What it measures

Measures vitamin B12, needed for DNA synthesis in blood cells and for nerve function. Ordered for macrocytic anemia, neuropathy, cognitive symptoms and in people at risk of deficiency.

Specimen and preparation

• Specimen: Serum, protected from light
• Tube: Gold top
• Preparation: Overnight fasting preferred. Collect before B12 injections or transfusion.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• B12 supplements or injections
• Liver disease
• Myeloproliferative neoplasms (e.g. CML)
• Renal failure

Causes of low values

• Pernicious anemia
• Strict vegan diet
• Gastric or ileal surgery, Crohn disease
• Metformin or long-term acid-suppressant use
• Fish tapeworm infection

Method

Competitive chemiluminescent immunoassay using intrinsic factor

Good to know

Borderline results should be checked with methylmalonic acid or holotranscobalamin. Anti-intrinsic factor antibodies can falsely raise B12 in some assays.

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