Biotin: Good for Hair and Nails, Bad for Thyroid Lab Tests
The new study conducted in a rural Michigan family medicine clinic is only the second to examine the prevalence of use of products containing high-dose biotin (vitamin B7), which interferes with a variety of biotin-based laboratory immunoassays. In 2017, and again in 2019, the US FDA issued warnings about biotin interference causing falsely low troponin readings leading to missed diagnosis of myocardial infarction.

A survey of 249 people seen at the rural Michigan clinic. In all, 7.2% reported taking more than 5 mg daily of biotin. That proportion is similar to the 7.7% previously reported in an outpatient setting and 7.4% as indicated by serum levels of patients who presented to an emergency department. Among 249 with complete survey data, 20.4% reported taking biotin-containing products, and of these, 87% were women. Of the 54 patients who reported taking biotin, 17 (31.5%) patients — 6.8% of the total 249 patients — reported taking daily doses of more than 5 mg.

Biotin interference can also result in falsely elevated triiodothyronine and thyroxine, and falsely low thyroid stimulating hormone, mimicking results seen in hyperthyroidism (Graves disease). This can lead to unnecessary workup and treatment, with associated costs and side effects.

A sizeable proportion of people use cosmetic products containing enough biotin to interfere with several laboratory measurements, including those of thyroid function.