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The FDA Warns That Biotin May Mask Test Results

The FDA Warns That Biotin May Mask Test Results

Before you start supplementing, talk with your doctor.

In the 1994 Jim Carrey film, The Mask, timid bank clerk Stanley Ipkiss discovers a magical mask, which transforms him into a manic, confident (and green) playboy with supernatural powers.

As the movie showed, masking can cause a lot of trouble. The FDA warned that too much biotin (vitamin B7) can mask test results for a clinical biomarker—troponin—that helps docs diagnose heart attacks. And high doses of biotin can also skew test results for thyroid hormones, which can lead to an over-diagnosis of Graves’ disease or hyperthyroidism.

But biotin can cause even more masking trouble. A case report in the Journal of the Endocrine Society reveals that someone taking 5,000mcg of biotin daily (a common dosage sold OTC, even though 30mcg is adequate for good skin, nail and liver health) seemed to test positive for hypercortisolemia, believed to be caused by a testosterone-producing tumor. That, the report says, “led to weeks of psychological distress ... nearly resulting in an unnecessary invasive procedure.”

Moms-to-be and breastfeeding moms may need to take B7 (ask your doc—the dose in a prenatal multivitamin usually suffices) to assure proper fetal development and infant health. But the rest of you—if you have two to three daily servings of 100 percent whole grains, eat walnuts, pecans and almonds, and have at least a couple of servings of wild salmon and trout each week … you likely don’t need biotin supplements.

Medically reviewed in April 2020.

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