Bewildered by Biotin

Abstract

Over the past few years, biotin has become one of the most popular and widely used over the counter supplements, with claims of improving hair, skin, and nails. While the daily requirement for biotin is around 30–70 mcg, most supplements contain high doses of 5000–20,000 mcg (5–20 mg). These supplements result in blood levels of biotin that can interfere with common laboratory assays, specifically those using biotin–streptavidin chemistry. In the presence of high blood levels of biotin, the assay can lead to abnormally low (such as with TSH and PTH) or abnormally high (such as fT4, fT3, and cortisol) results. When coupled with patient symptoms or certain clinical situations, these abnormal laboratory results can lead to misdiagnosis of an endocrine disorder or can confound management of a true endocrine condition. Clinicians need to be aware of the effects of biotin on a wide variety of laboratory measurements and take precautions to avoid errors related to biotin interference. This can require an intentional approach, including close scrutiny of all supplements utilized by their patients as the biotin content may not be immediately obvious. Fortunately, withholding the biotin-containing supplements for an adequate time frame to permit a sufficient reduction in the biotin blood levels will allow accurate laboratory assessment.