Biotin: The 'Harmless' Supplement That May Mask Signs Of Cancer And Confuse Medical Tests

Thousands of cancer patients are taking a popular hair loss supplement without realizing the hidden risks. Now, scientists are warning that biotin can distort important medical tests, mask signs of the disease, and even delay treatment. What seemed like a harmless vitamin may be directly interfering with the fight against cancer.

Hair loss caused by cancer treatment can be emotionally devastating. In search of quick solutions, many patients turn to biotin, a supplement widely promoted on social media as capable of strengthening hair and nails.

However, scientists and doctors are now issuing an important warning: despite its reputation as a "harmless vitamin," biotin can interfere with essential laboratory tests for monitoring cancer, generating false results that can delay diagnoses, mask disease recurrence, or even alter important medical decisions.

Biotin, also known as vitamin B7, participates in the production of keratin, a protein fundamental to hair, skin, and nails. Therefore, it has become extremely popular in beauty and hair growth products.

The problem is that few studies have actually demonstrated consistent benefits of supplementation in people without a vitamin deficiency. Since biotin is already present in many common foods, such as eggs, meat, milk, fruits, and vegetables, true deficiency is rare. Even so, thousands of cancer patients begin taking high doses on their own, usually influenced by information found on the internet or social media.

To understand the risks of this habit, researchers reviewed clinical studies, laboratory data, and reports from cancer patients. The scientists analyzed how biotin affects tests routinely used to monitor different types of cancer, including prostate, breast, ovarian, and thyroid cancer.

Many of these tests work using a chemical reaction based on the binding between biotin and a protein called streptavidin. When there is excess biotin circulating in the blood, this reaction is "cheated," producing artificial results that do not reflect the patient's true condition.

Treatment for hair protection in cancer patients

Researchers explain that this can lead to serious consequences. In some tests, hormone levels may appear falsely low, while in others they may appear artificially high. For example, prostate-specific antigen tests, used to monitor prostate cancer, may indicate low levels even when the tumor is returning.

Hormones such as estrogen and testosterone may appear elevated when they are not, leading doctors to postpone important treatments. Biotin can also interfere with emergency cardiac tests, such as troponin, used to detect heart attacks.

Scientists also analyzed the behavior of cancer patients facing hair loss. In research conducted with support groups, many reported that oral supplements were their first choice to try to regrow their hair, often without consulting oncologists or dermatologists.

One of the accounts described in the study shows the case of a breast cancer patient who began taking large amounts of biotin after finding recommendations online. During medical follow-up, her tests began to show inconsistent results that did not match her actual symptoms. Only later did she discover that the supplement might be causing the laboratory confusion.

Anna Malagoli, a breast cancer survivor, was taking biotin to regrow her long curls until her oncology doctor warned her that it could affect her treatment and tests. Credit: Ohio State University Comprehensive Cancer Center

In addition to the scientific review, the authors compared the evidence on different treatments for cancer-related hair loss. They highlight that minoxidil, an approved and over-the-counter medication in several countries, has much stronger scientific backing.

In controlled clinical studies, patients who used minoxidil showed significant improvement in hair growth after chemotherapy, with few side effects. According to experts, it represents a safer and more reliable alternative for patients who wish to stimulate hair growth without compromising important tests.

More than half of the cancer patients Dr. Brittany Dulmage treats for hair loss at the Ohio State University Comprehensive Cancer Center have started taking a nutritional supplement on their own initiative or on medical advice. Instead of biotin, Dr. Dulmage recommends that patients take a prescription supplement that is safe for widespread use. Credit: Ohio State University Comprehensive Cancer Center

Researchers emphasize that there is no evidence that biotin directly increases the risk of cancer progression. The main concern is another: its ability to interfere with essential medical tests precisely at a time when quick and accurate decisions can be life-threatening for the patient.

Therefore, scientists urge doctors to discuss supplements more openly during cancer treatment and advise patients about the risks of starting seemingly "natural" products without professional guidance.

READ MORE:

Biotin Supplements for Hair and Nail Regrowth: A Caution for Oncologists

Layna Mager, Olivia Ueltschi, Lucy Rose, and Brittany Dulmage.

JCO Oncol Pract 22, 730-731(2026). Volume 22, Number 5

DOI: 10.1200/OP-25-0069