Biotin: Good for Hair and Nails, Bad for Thyroid Lab Tests

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

The clinical takeaway, two endocrinologists told Medscape Medical News during the American Association of Clinical Endocrinology (AACE) Annual Meeting 2022, is that if an asymptomatic patient’s thyroid test comes back suggesting hyperthyroidism, ask if they’ve been using hair, skin, or nail products containing biotin.

If they have, advise them to stop taking the supplement for a week and then re-measure their thyroid hormone levels. Chances are, they’ll normalize.

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 Food and Drug Administration issued warnings about biotin interference causing falsely low troponin readings leading to missed diagnosis of myocardial infarction.

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.

About 7% of Patients Found to Be Taking High-Dose Biotin

Jenna Bernson, MD, of Michigan State University, presented a poster at the AACE meeting detailing the new findings from 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, both reported in 2018 in a single paper from the Mayo Clinic.

Study coauthor Saleh Aldasouqi, MD, also of Michigan State University, told Medscape Medical News: “We know people take biotin as a hair product, a skin product, and as an energy supplement…Our hypothesis was that maybe biotin use might be less in rural women, but it’s about the same.”

The biotin dose found in vitamin supplements, about 50 µg, is roughly the daily requirement for the human body and doesn’t typically interfere with lab results.

The problem comes with the far higher doses used in cosmetic products, Aldasouqi said. “The typical beauty tablet has 5 to 10 mg, so taken twice a day, that’s 10,000 µg. That is what would interfere with the labs.”

Advise Patients to Stop Taking Biotin a Week Before Lab Work

“It’s very important that we ask our patients about biotin,” added Cheryl Rosenfeld, DO, an endocrinologist in private practice in Parsippany, New Jersey.

“I tell my patients, if it’s helping you and it’s growing your hair and nails and you look great, by all means, you can take it. You just have to stop it a week before you get your labs done, just to be safe,” she told Medscape Medical News.

Indeed, Aldasouqi said that although some guidelines — including guidance from the American Association for Clinical Chemistry — suggest stopping biotin 3 days in advance of lab work, “that’s not enough. It’s easier for patients to remember a week.”

Rosenfeld also pointed out that women aren’t the only ones taking biotin for beauty. “Biotin products are marketed to men for beard thickening…There are preparations for hair, skin, and [for] nails for men and women.”

Interference Varies by Laboratory

The survey was distributed in a family medicine rural health clinic in Alma, Michigan, with a population of about 9000. Of a total of 264 patients who filled out surveys between March 2021 and January 2022, 66.3% were women. 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.

In addition to asking patients about their biotin use, “it is prudent to be familiar with the local laboratory and what tests are susceptible to biotin interference at each facility,” the researchers note in their poster.

Indeed, Rosenfeld said, “Some labs are better than others. The assays differ. Some may work better, but in others, the interference is so bad.”

Aldasouqi noted that Abbott Laboratories’ tests are not affected by biotin. The company did not fund this study, although he now consults for them.

Rosenfeld, who practices in suburban New Jersey, said: “You can’t go a mile without tripping over a nail salon where I live. So basically, I see [biotin use] a lot. If I were to repeat [the Michigan] study, I’m sure it would be higher.”



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