Definition

Measures the amount of vitamin B12 in the blood. Most often ordered when other blood tests suggest megaloblastic anemia.

Purpose

To detect B12 deficiency and distinguish between types of anemia. Commonly evaluated together with folate (B9).

Results

Values below 299 pg/mL (219 pmol/L) suggest possible B12 deficiency; symptoms are likely to develop at this level.

Important: Deficiency must be confirmed by measuring methylmalonic acid (MMA) levels; elevated MMA indicates true B12 deficiency.

Normal Values

299 to 1054 pg/mL or 219 to 773 pmol/L.

Normal reference ranges may vary slightly between laboratories; some laboratories use different units of measurement or test different samples.

Risks and Limitations

Serum B12 level alone can be misleading; confirmation with MMA and homocysteine is recommended for borderline values.

Related Tests

Folic Acid (Folate, Vitamin B9)

Folic acid is also known as vitamin B9. It helps in the formation of red blood cells and in DNA production. The test measures its amount in the blood.

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Homocysteine

Homocysteine is an amino acid; the body uses amino acids to build proteins. The body breaks down homocysteine with the help of B vitamins (B6, B12, and folic acid).

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Complete Blood Count (CBC)

A group of tests that measures the number and size of the cells in the blood. Red blood cells (erythrocytes), white blood cells (leukocytes), platelets, hemoglobin, hematocrit and

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Ferritin

Ferritin is the protein that stores iron in the body. The ferritin level in the blood is an indirect indicator of the body's total iron stores.

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Other related tests not yet in the glossary: Methylmalonic Acid (MMA).