Nov. 29, 2017 -- The FDA is warning that high doses of vitamin B7, or biotin, in dietary supplements can interfere with hundreds of common lab tests -- including some that emergency room doctors rely on to diagnose a heart attack. The problem has led to at least one death.

Biotin is in many multivitamins. It’s also sold in formulas that are marketed to improve hair and nail growth. A 5- to 10-milligram dose -- an amount that’s commonly added to supplements -- is 166 times to 333 times more than the 30 micrograms most people need in their diets every day.

Doctors sometimes prescribe high doses of biotin to treat nerve pain called neuropathy. It is also being studied as a treatment for multiple sclerosis.

In some cases, extra biotin causes falsely high results on tests. In others, it causes the results to read as falsely low.

That’s true with some ways to detect a protein called troponin, which rises after heart muscle has been damaged. Doctors use the troponin test in the emergency room to find out whether a patient’s chest pain is from heartburn or a heart attack.

The FDA says a patient who was taking high levels of biotin died when a troponin test failed to show he was having a heart attack.

Too much biotin in lab tests for thyroid hormones has led doctors to diagnose Graves’ disease in children and adults. Graves’ is an autoimmune disease that causes too much thyroid hormone in children and adults. Biotin in supplements can also affect tests for heart failure, pregnancy, cancer, and iron-deficiency anemia.

Experts say the problem is not new.

“In the lab community, people have known about this for a long time,” said Danni Li, PhD, director of clinical chemistry at the University of Minnesota Medical Center.

Li and her colleagues demonstrated this problem with an experiment. They asked six healthy adults to take 10 milligrams of biotin as a dietary supplement for a week. They tested their blood before and after they took the supplements for nine different hormones, a cancer marker, and iron. About 40% of the tests were thrown off by the supplements. Their study was published in September.

Li says she’s not sure how many doctors or patients have been aware of the issue. When she saw the FDA warning, she immediately sent it to all of her hospital’s emergency room doctors.

Another expert says he was relieved to see the FDA raise a red flag.

“For the last couple of years, I have been trying to raise the profile of this issue and get it to the attention of people who might be able to fix it. I’m glad to see this [FDA warning]” says Earle Holmes, PhD, a professor of molecular pharmacology and therapeutics at Loyola University School of Medicine in Maywood, IL.

Holmes and his team reviewed 374 tests that run on some of the most popular lab testing machines in the U.S. He found that 221 of them use biotin in their test. About 80 of these tests came with instructions that indicated they could be skewed by extra biotin in a patient’s blood.

The FDA says it is “working with stakeholders to better understand biotin interference with laboratory tests, and to develop additional future recommendations for safe testing in patients who have taken high levels of biotin when using laboratory tests that use biotin technology.”

To stay safe, Li says patients should check their vitamin bottles for biotin. Learn how much you’re taking, and tell your doctor you’re taking it at your next visit. She says lab directors can sometimes change tests if they think biotin might be a problem.

“This is a message that needs to get out,” says Lynn Burmeister, MD, an endocrinologist and associate professor of medicine at the University of Minnesota.

For patients that have lab tests planned, she tells them to stop taking their supplements.

“If I can control what my patients are doing, I tell them to stop biotin for 1 week,” Burmeister says.

Other doctors say it’s probably also wise to consider whether you need to be taking biotin at all. Foods containing the vitamin include liver, egg yolks, fish, meat, seeds, nuts, and some vegetables, such as sweet potatoes.

“Biotin is in many supplements sold to improve skin and hair; however, the science supporting biotin for these indications is quite weak, so I don't recommend it to any of my patients,” says Pieter Cohen, MD, a researcher at Harvard and associate professor of medicine at the Cambridge Health Alliance in Somerville, MA.

Show Sources

Danni Li, PhD, assistant professor, department of laboratory medicine and pathology, University of Minnesota Medical Center, Minneapolis.
Lynn Burmeister, MD, associate professor of medicine, Division of Diabetes, Endocrinology and Metabolism, University of Minnesota, Minneapolis.
Earle Holmes, PhD, professor of molecular pharmacology and therapeutics, Loyola University School of Medicine, Maywood, IL.
Pieter Cohen, MD, associate professor of medicine, Cambridge Health Alliance, Somerville, MA.
Archives of Pathology & Laboratory Medicine: “Biotin Interference in Clinical Immunoassays: A Cause for Concern.”
Journal of the American Medical Association: “Association of Biotin Ingestion With Performance of Hormone and Nonhormone Assays in Healthy Adults.”
National Institutes of Health: “Biotin.”

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