How Biotin Could Mess With Your Blood Work

If you read our website and our magazine, you know that we've long explored the benefits of biotin, also known as vitamin B7, which has been linked with increased hair growth. As we reported in our 10 Secrets to Gorgeous Long Hair, studies have shown biotin elongates the follicle, which in turn makes hair grow faster; biotin also stimulates the cells that cause your hair to grow. Although both of those claims have never been substantiated by the FDA, we've heard enough testimonials from readers, hairstylists, and even celebrities that the vitamin really does work. And it's because of those very studies and anecdotal reports that biotin pops up in a lot of multivitamins and supplements like Viviscal and Elon Matrix 5000, which are specifically marketed and targeted to enhance hair growth. It's also the best-selling supplement on Amazon. (Who knew?)

But new research shows that biotin could have a shady side. A study in Clinical Laboratory News found that taking high doses of the vitamin might actually skew diagnostic test results, leading to false-positives or false-negatives for pregnancy, fertility, and even cancer screenings and monitoring. "Some blood tests use biotin to bind hormones to the test tube," explains Guiseppe Barbesino, an endocrinologist at Massachusetts General Hospital and an assistant professor of medicine at Harvard Medical School. "If you have a lot of biotin in your blood, that will bind to the test tube and the hormones or other chemicals being tested won’t find space to bind."

Before you get worried, it's important to note that the binding effect is most significant if you're taking mega-doses of biotin. Most people using it for beauty purposes are taking lower dosages of anywhere from 2.5 to ten milligrams, which is an amount that should have a subtle effect at most, but even a subtle effect may be relevant in some tests that require a high level of precision, says Barbesino. One tablet of Viviscal Extra Strength, for instance, has 120 micrograms, or .12 milligrams, an amount that should not have any effect, according to Barbesino. If you're just looking for longer nails, your odds of a serious misdiagnosis are slim. Still, since it's an are that needs more research, Barbesino recommends erring on the side of caution: That is, if you're going for a blood test, tell your doctor and hold off on your biotin for two to three days before it.

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More tricks for glow-y skin:

1. 18 Superfoods That Can Serve Up Gorgeous, Glowing Skin, According to Derms
2. This Really Weird Trick for Glow-y Skin Actually Works
3. The Top 10 Highlighters the Internet Loves for Glow-y Skin

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And if you’re still worried or nervous, remember this: Biotin is literally a supplement—as in, not a biological necessity, and halting your vitamin routine won't impede your hair's natural growth. But if you’re into biotin’s benefits and don't want to stop, consider it fair game—as long as your doc is in the loop.

Now, watch how to make your hair look thicker: