Biotin supplementation may interfere with cancer testing, researchers warn

US researchers caution that biotin (vitamin B7) supplements, for hair, skin, and nail health, may interfere with cancer lab results. They also suggest there is limited scientific evidence that these products promote hair and nail growth for those living with or recovering from cancer. 

Specifically, biotin can mask changes in prostate, thyroid, ovarian, and breast cancers, note the researchers. Some lab tests rely on a chemical reaction involving biotin, so when patients take biotin supplements, lab results may falsely be high or low.

Nutrition Insight speaks with Brittany Dulmage, M.D., associate director of dermatology at the Ohio State University Comprehensive Cancer Center, US. She is also a director of the Oncodermatology Clinic, which addresses hair, skin, or nail side effects from patients’ cancer treatment such as chemotherapy, immunotherapy, or targeted therapy.

“The reason that biotin interferes with assays is that the assays themselves use biotin in their design,” she highlights. “More specifically, many lab tests use a very strong ‘lock-and-key’ system made of two parts: biotin and streptavidin.”

This pair of compounds works well for tests to identify cancer because the biotin and streptavidin have a strong interaction.

“In these tests, the biotin may be attached to antibodies, called biotinylated antibodies, that are designed to measure the level of a specific hormone or other molecule,” explains Dulmage.

“If a patient’s blood contains excess biotin, this excess biotin can either compete with the test’s biotin or block streptavidin from interacting with the biotinylated antibodies.”

Potential risks

For many cancer patients, hair loss is one of the most distressing side effects of their therapy. Increasingly, they have been taking oral supplements of biotin, which are marketed to consumers for their potential to improve hair regrowth and brittle nails.

For patients who want to continue taking biotin supplements, Dulmage recommends stopping them at least 72 hours before blood work.

On a mission to raise awareness about the unintended consequences of taking biotin, Dulmage led a team of researchers in publishing an article in JCO Oncology Practice. They urge oncologists to routinely talk with patients about their hair loss and educate them about how biotin could affect their test results.

“Biotin does not actually change the levels of hormones in the body, but it interferes with the way those levels could be checked when blood work is done,” says Dumage.

“For some of the hormones, such as prostate-specific antigen or thyroid-stimulating hormone, it may falsely suppress or lower those levels, potentially masking cancer recurrence in cancer survivors. For reproductive hormones, including estrogen and testosterone, it may falsely elevate levels, resulting in delayed therapy.”

She notes that biotin at 5 mg and higher can pose a risk, with doses above 20 mg posing an exceptionally high risk. “I am seeing it both with standalone high-dose biotin products and multi-ingredient supplements. I have not seen issues with biotin-fortified foods.”

“Oftentimes, patients are taking more than one multivitamin or supplement that contains biotin, so they should be considering the cumulative dose of all individual vitamins and supplements.”

72-hour wash-out period

For patients who want to continue taking biotin supplements, Dulmage recommends stopping them 72 hours before blood work.

“The challenge is that not all blood work is planned, so you may not be able to hold your biotin. Biotin can also impact the levels of troponin, which is a marker of whether or not someone is having a heart attack,” she explains.

“Obviously, you’re not planning to have a heart attack, so you can’t hold biotin before troponin levels are checked. This is why I recommend to patients — think about not taking it at all, especially since very few people are biotin deficient.”

Dulmage’s team highlights that the US FDA-approved oral minoxidil drug is a safe, effective alternative to biotin supplements, and requires a prescription. For hair loss, Dulmage recommends patients take minoxidil instead of biotin supplements, underscoring that it is both effective and safe, except for those who are pregnant or breastfeeding.

Dulmage highlights that the US FDA-approved oral minoxidil drug is a safe, effective alternative to biotin supplements, and requires a prescription.Additionally, over-the-counter minoxidil is FDA-approved for hair loss and available in topical forms such as lotions or foams.

“If you have been trying minoxidil for several months and not seeing any improvement, or want to know about other options, see a dermatologist. There are many other types of treatments that may be an option,” says Dulmage.

Tackling consumer misinformation

Reflecting on who should bear the responsibility of disseminating consumer information, Dumage comments: “This is a bit out of my scope as a clinician, but I do think it would be helpful to have a warning printed on the label explaining the risk of biotin with lab assays and the need to hold biotin for up to three days prior to planned bloodwork.”

“There is a great need for increased education of practitioners and consumers with regard to the effect of supplements, including both the efficacy of a particular supplement and any potential safety issues. In the case of biotin for hair growth, there is both a lack of evidence of real efficacy and a potential safety issue.”

She adds that more than half her patients with a problem related to hair loss are on a supplement that they’ve started on their own after learning about it online, by word of mouth, and sometimes even at the advice of their doctor.

One patient from Columbus, Anna Malagoli, was concerned about the side effects of her breast cancer treatment, in particular, hair loss. After her cancer went into remission, she began taking biotin supplements based on information she read online to regrow her long curly hair.

“The amount of information on the Internet can lead you in different directions. I was taking so much biotin it’s not even funny,” she says. “Nobody mentioned one word that biotin supplements could interfere with your treatment or your testing.”

“My lab results were inconsistent. They just didn’t balance out with what I was feeling, so that was a red flag. I think it had to do with the supplements I was taking.”

Malagoli has taken minoxidil and biotin supplements and has noticed less effectiveness from the biotin.

“I don’t know if my body just doesn’t assimilate the supplements as well, but minoxidil is definitely more effective long-term,” she says. “I would say it’s super important to listen to your doctors and not just do your thing.”