• The FDA recently issued a warning regarding the potential interference of biotin (vitamin B7) with laboratory tests: (https://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm586505.htm)

• Extremely high concentrations of circulating biotin can significantly interfere with immunoassay tests, leading to either falsely decreased or falsely increased results depending on the assay.  This interference was discussed in a recent JAMA article (https://jamanetwork.com/journals/jama/fullarticle/2654822).

• A partial list of potentially affected tests is shown below and a full list can be found here:

Falsely increased results	Falsely decreased results
Thyroid hormones (T4 and T3) Folate Vitamin B12 Cortisol DHEA-S Estradiol Testosterone	Troponin T TSH NT-proBNP Prolactin hCG CA 125 Ferritin

• Such elevated concentrations of biotin are unusual, but can be achieved following recent use of dietary/therapeutic supplements with biotin content greatly exceeding (i.e., >5 mg/day) nutritional requirements. Many of these supplements are over-the-counter products promoted for cosmetic benefits.

• The laboratory cannot detect biotin interference. Patients should be asked if they have consumed biotin-containing supplements and, if so, should wait at least 12 hours before specimen collection for laboratory tests.

• To better inform providers and patients of the laboratory tests potentially affected by biotin, we have updated our pathology handbook as well as comments appended to test results.

• Various mailout tests may also be affected by high-dose biotin. There is no alternate testing available in most cases.

Questions should be directed to Anna Merrill, PhD (678-8400, anna-merrill@uiowa.edu) or Matthew Krasowski, MD, PhD (384-9380, matthew-krasowski@uiowa.edu).