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.