Causes of spuriously high or low vitamin B12 levels

Conditions or exposures that spuriously decrease vitamin B12 levels^*

Multiple myeloma
HIV infection
Pregnancy
Oral contraceptives
Diphenylhydantoin

Conditions or exposures that spuriously increase vitamin B12 levels^¶

Occult malignancy
Myeloproliferative neoplasms
Alcoholic liver disease
Kidney disease
Certain inborn errors of metabolism
Nitrous oxide exposure^Δ

Refer to UpToDate for further discussion of the difference between total versus functional vitamin B12 levels and an approach to the evaluation of vitamin B12 deficiency in individuals with these conditions.

HIV: human immunodeficiency virus.

* These conditions may result in low vitamin B12 levels without functional B12 deficiency.

¶ These conditions may result in normal vitamin B12 levels when the patient is functionally vitamin B12 deficient.

Δ Nitrous oxide exposure can also impair vitamin B12 activity despite normal vitamin B12 levels.

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Causes of spuriously high or low vitamin B12 levels