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We’re not quite sure when the buzz began about biotin, but suddenly, it seemed, every woman we knew was taking the vitamin—also called B7 or vitamin H—to support hair and nail growth. And indeed, while research is sparse, at least one double-blind study concluded that Viviscal, a supplement containing biotin, not only supported hair growth but also helped to prevent the shedding associated with hair loss in women.

But do the risks outweigh the rewards? The Food and Drug Administration is now warning that high doses of biotin can confuse the results of hundreds of common lab tests, including some used to diagnose a heart attack, cancer and even pregnancy. In some cases, the presence of the vitamin caused lab results to skew high, while in others, results were misleadingly low.

Though the FDA doesn’t raise any health concerns about taking biotin—which is occasionally prescribed in high doses to treat nerve pain—an overabundance of biotin in the bloodstream can also skew the results of thyroid tests, occasionally leading to false diagnoses of Graves’ disease in adults and children.

While this is news to us, lab technicians have apparently been aware of this complication for some time, and are relieved that the FDA is finally raising a red flag about the issue. As quoted by WebMD, Dr. Lynn Burmeister, an endocrinologist and associate professor of medicine at the University of Minnesota says, “This is a message that needs to get out.”

And how much biotin should we actually be taking? Approximately 30 micrograms per day; which means that the 5- to 10-milligram dose commonly added to supplements is an estimated 166 to 333 times more than the average person needs.

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It’s also worth noting that most of us don’t suffer from biotin deficiency, since it’s found in foods like egg yolks, fish, meat, seeds, nuts and sweet potatoes.

So while we all want gorgeous hair and strong nails, it’s best to be on the safe side.

For biotin devotees, Burmeister advises stopping the supplement at least one week prior to any planned lab tests.