A warning for people who take the dietary supplement biotin (vitamin B7): the FDA says taking too much of the vitamin may interfere with the results of some lab tests. Biotin is often included in multivitamins, prenatal vitamins, and dietary supplements marketed to improve nails, hair, and skin. While there's no recommended dietary allowance established for biotin, the adequate intake value is 30 micrograms per day for people ages 19 or older and for pregnant teens and women. But biotin supplements may contain up to 650 times the adequate intake. The FDA warns that taking too much biotin can interfere with lab tests, such as hormone tests and tests for markers of heart attacks (like troponin). An inaccurate lab result can have dangerous consequences. For example, the FDA reports that one person taking high levels of biotin died after a falsely low troponin test result. The FDA also notes it's seeing an increase in reports of biotin interference in lab work. The bottom line: Always tell your doctor which supplements you're taking. And remember, most people can get enough biotin from a healthy diet that includes seeds, nuts, meat, fish, eggs, and certain vegetables (such as spinach and broccoli).
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