Vitamins and supplements are typically thought of as a health booster. Now they’re becoming increasingly used in the beauty industry as a way to get a healthy glow from within.

But researchers have a new warning about one popular supplement called biotin: It can affect the results of your medical tests.

Biotin is one of the most common supplements on the market.

“Biotin, one of the subtypes of vitamin B, has important functions in the metabolism of protein,” said Dr. Michael Grosso, chief medical officer at Northwell Health’s Huntington Hospital in Huntington, New York.

A biotin deficiency can cause a host of symptoms, including disorders of the nervous system, Grosso explained. But that’s not the common reason that people take supplements with this vitamin.

“Biotin has become extremely popular as a beauty aid, with putative effects on the skin and nails,” he said.

This idea came about from studies that found biotin supplementation improved hoof health in horses.

But now, due to the supplement’s increasing popularity, researchers are discovering it can alter the results of some medical tests.

A new review published in the Journal of Applied Laboratory Medicine looked at several studies published between 2012 and 2017 that found biotin interference in medical tests.

Biotin is commonly used as a reagent — a compound that helps chemical reactions take place — in medical tests, explained study co-author Dina N. Greene, PhD, associate director of chemistry at the University of Washington. It acts as a bridge between antibodies and whatever you’re trying to detect.

“But we weren’t used to having so much excess biotin in the sample, which can change how the test works,” she said.

Where the excess biotin is coming from

Many multivitamins and B-complex vitamins contain biotin, but typically in smaller amounts than biotin supplements.

In B-complex vitamins, the dosage is generally between 10 to 100 percent of the Daily Value (DV). This isn’t close to the megadoses seen in biotin supplements or multivitamins marketed to women, which are specially formulated supplements for hair and nails.

SugarBearHair supplements, popularized on social media by celebrities like Kylie Jenner and Vanessa Hudgens, contain 1,667 percent of the DV, while One A Day Women’s multivitamin contains 3,333 percent of the DV.

That excess won’t necessarily hurt you. Biotin is water-soluble, so you’ll just pee it out — but it’s also not necessary, said Greene.

Who needs biotin?

Biotin is found in foods like eggs, fish, meat, seeds, nuts, and vegetables like spinach, broccoli, and sweet potato, according to the National Institutes of Health. A diverse diet should cover your adequate intake, the level assumed to ensure nutritional adequacy.

“In people that have an enzyme deficiency that makes them unable to process biotin, then they need a lot of excess biotin. It’s also used in some very specific multiple sclerosis treatments, but the average person does not need to be supplementing with biotin,” said Greene.

In fact, biotin deficiency is so rare that there’s no Recommended Daily Allowance for it.

The dangers of biotin interference

Immunoassays, the type of medical tests that often use biotin, are fundamental to laboratories. These tests including routine lab work that checks for hormones, thyroid function, pregnancy, and heart attack markers, said Greene.

When excess biotin interferes with these tests, it can produce false positives or false negatives, depending on the way the test is designed. Getting the wrong test result can be deadly.

“For heart attacks, there has been a reported case of it causing a false negative that led to missing the diagnosis of a heart attack, which led to patient death,” said Greene.

Another known interaction with thyroid tests can lead to the results that you would expect for hyperthyroidism, or an overactive thyroid.

That could lead someone to be unnecessarily treated for the condition.

How to prevent biotin interference

Informing your doctor of any supplements you’re taking is a step in the right direction for preventing any testing errors.

If you need to take biotin for medical reasons, there are available methods to compensate for the extra biotin that laboratories can utilize, said Grosso.

If it’s not medically necessary, Greene recommends not taking biotin-containing supplements 48 hours before a primary care visit that might include blood work.