Doctors Warn Popular Vitamin Supplements May Interfere with Cancer Treatment and Diagnostic Tests - Video

A vitamin many people take for healthier hair could quietly interfere with cancer care in ways patients never expect. Doctors are now warning that biotin supplements, often marketed for hair and nail growth, may distort important lab test results used to monitor cancer and other serious conditions.

The findings are published in the journal JCO Oncology Practice.

Hair loss is one of the most distressing side effects of cancer treatment, leading many patients to search for solutions online or through over-the-counter supplements. But according to experts at The Ohio State University Comprehensive Cancer Center, there is little strong evidence that oral biotin actually improves hair growth after cancer therapy.

More importantly, biotin can interfere with several blood tests. Some cancer monitoring tests rely on chemical reactions involving biotin. As a result, supplements may falsely lower or raise hormone levels and tumor markers.

For example, biotin may falsely suppress prostate-specific antigen (PSA) or thyroid-stimulating hormone (TSH) levels, potentially hiding signs of cancer recurrence. It can also falsely elevate hormones such as estrogen or testosterone, which may delay treatment decisions.

The risks are not limited to cancer monitoring. Biotin may also interfere with troponin testing, a blood marker used to detect heart attacks.

Researchers say true biotin deficiency is rare because the vitamin is already found naturally in foods like eggs, dairy products, vegetables, meat and fruits. Instead of supplements, doctors recommend evidence-based treatments such as minoxidil for managing hair loss during or after cancer treatment.

Experts advise patients to stop taking biotin at least 72 hours before scheduled blood tests if they continue using it. However, many specialists now suggest avoiding unnecessary biotin supplements altogether, particularly during cancer treatment and recovery.

REFERENCE: Layna Mager, Olivia Ueltschi, Lucy Rose, Brittany Dulmage. Biotin Supplements for Hair and Nail Regrowth: A Caution for Oncologists. JCO Oncology Practice, 2025; DOI: 10.1200/OP-25-00693