Can taking prenatal vitamins cause a false positive

• Biotin is the main vitamin in supplements that promise to improve your hair and nails.
• The FDA just released a warning about these supplements because they can skew the results of blood tests.
• Very high levels of biotin could cause a false positive on a pregnancy test or a false negative in a cancer screening.

Biotin, promoter of "Cher hair" and Rihanna-worthy nails, has always been a little controversial since claims that the vitamin can help you grow Rapunzel-length strands have never been substantiated by the FDA. Now, a new FDA warning outlines another caveat to consider before taking biotin: It could mess with blood test results.

Last year, we reported on a study suggesting that taking high doses of biotin could skew certain diagnostic test results leading to false positives or false negatives for everything from pregnancy to cancer. In a statement released this week, the FDA has confirmed the concern. "The FDA is alerting the public, health care providers, lab personnel, and lab test developers that biotin can significantly interfere with certain lab tests and cause incorrect test results which may go undetected," the statement reads.

Here's the deal: Biotin in your body (whether it comes from your diet or from popping a pill) bonds with certain proteins, which can be measured to detect a variety of health conditions. Doctors can measure your biotin levels as a way to determine the presence of said protein markers, but if you're taking a biotin supplement, that can make the test results inaccurate.

These falsely skewed tests could lead to serious consequences. According to the statement, "the FDA has seen an increase in the number of reported adverse events, including one death, related to biotin interference with lab tests."

Biotin is a natural vitamin — we get it from food like eggs, whole grains, and almonds, so in the right amounts, it's not a problem. The risk of ruining important test results comes into play with supplements, which can have up to 650 times the recommended daily intake of the vitamin, says the FDA. It's this level of biotin that could cause a false positive on a pregnancy test or a false negative in a cancer screening.

To avoid a potentially dangerous test result, make sure your doctor knows if you're taking biotin (remember, it might be in your multivitamin or prenatal vitamin even if you're not taking a specific supplement, adds the FDA) and that any lab you go to for blood work knows as well. "It's important to discuss any supplements (over-the-counter, vitamins, minerals, etc.) you are taking with your doctor because these supplements can have potentially adverse effects," says Sejal Shah, a dermatologist and founder of SmarterSkin Dermatology in New York City. "Just because something is OTC or natural doesn't mean that it is completely harmless."

If you think biotin might have played a role in the results of a recent lab test, report it to the FDA. "If you suspect or experience a problem with a laboratory test while taking biotin, we encourage you to file a voluntary report through MedWatch, the FDA Safety Information and Adverse Event Reporting program," the agency says.

The bottom line: Let your health-care team know you're popping extra biotin. Your doc will advise you what to do if you need biotin-based blood work.

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Biotin, also known as vitamin B7, is found in many beauty supplements that are marketed as hair, skin, and nail enhancers. But biotin – also known as vitamin B7 – can cause serious errors in medical test results.

In the past two decades, the percentage of adults taking biotin supplements has significantly increased. In 1999, just 0.1% of all adults took 1 mg/day of biotin. By 2016, consumer totals rose to 2.8%. Women tend to take even more biotin – one in 20 (4.7%) reported taking the supplement in a 2020 study.

In 2019, the U.S. Food and Drug Administration (FDA) issued an updated advisory about interference between biotin supplementation and common blood tests. High levels of biotin in a patient's blood or urine samples can cause significantly incorrect lab test results. This can lead to incorrect diagnoses and improper treatment of conditions, such as ectopic pregnancy, miscarriage, or heart and thyroid issues.

How much biotin is safe?

The Institutes of Medicine recommends a daily biotin allowance of 30 mcg (0.03 mg) for most adults. Unfortunately, supplement labeling is not strictly regulated, and your product may include more B7 than you might think.

Many products offer mega-doses, with some touting 10,000 mcg (10 mg) or higher. That's more than 300 times the recommended allowance. If you're also taking a general multivitamin, you may be getting an even higher daily dose.

How biotin interferes with lab testing

Some lab assays use biotin during the testing process. Increased biotin from a patient’s blood sample can bond to specific proteins during the testing process, leading to inaccurately high or low test results.

3 lab tests women should know about (and how biotin affects them)

1) b human chorionic gonadotropin (hCG): That’s right, the pregnancy hormone. Having a high level of hCG can be an early indicator of pregnancy. We also test for hCG levels to determine whether a patient might be experiencing an ectopic pregnancy or miscarriage.

Biotin supplements can cause false low levels in blood tests. That means you may be pregnant or experiencing an ectopic pregnancy or miscarriage and might not know it. In urine tests, high levels of biotin may prevent the control line on your home pregnancy test from appearing, yielding invalid results.

2) Thyroid stimulating hormone (TSH): Thyroid dysfunction is common – 1 in 8 women has a thyroid problem. To diagnose new thyroid disease or assess an existing condition, we measure TSH levels. Too high and you may have hypothyroidism. Too low, you may have hyperthyroidism. Taking too much biotin can cause false low levels of TSH, which may prompt unnecessary treatment that can lead to actual thyroid issues.

Related reading: What women need to know about thyroid conditions

3) Troponin: Troponins are proteins found in muscles, including the heart. Elevations of certain troponins aid in the diagnosis of heart attacks. However, biotin supplementation can lead to falsely low troponin levels, which can delay diagnosis. This is especially alarming for female patients, since heart attack symptoms in women may be more subtle.

Missed heart attack diagnoses carry the risk of potentially serious clinical implications. The FDA has received a report that one patient taking high levels of biotin died following falsely low troponin test results.

Lab tests that involve the protein ferritin or these hormones listed here can also be skewed by biotin supplementation:

• Cortisol
• Estrogen
• Progesterone
• Testosterone

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