FOR PEOPLE LIVING WITH or recovering from cancer, hair loss caused by treatments like chemotherapy can be one of the most distressing side effects. And on social media, they may encounter ads for oral supplements that contain biotin, also called vitamin B7, that claim it can improve hair and nail growth. However, biotin may affect lab tests that can be important for people with a cancer history.
An article published Sept. 15, 2025, in JCO Oncology Practice points to research that shows biotin can interfere with some lab tests that doctors use to track cancer and see how well treatment is working. And while biotin may help improve hair and nail growth for people who have known deficiencies in vitamin B7, the study points out there is limited data to suggest it will help people with hair loss due to cancer treatment or other causes.
Some lab tests used in cancer rely on a chemical reaction that involves biotin, so when someone takes extra biotin from supplements, it can make results look higher or lower than they really are. For example, biotin can cause hormone levels to appear falsely elevated, leading oncologists to delay endocrine therapy in postmenopausal women with breast cancer. Likewise, it can cause prostate-specific antigen (PSA) levels to appear lower than they actually are, masking cancer recurrence in prostate cancer survivors.
Tests that can be affected by biotin are also used in care for thyroid, endometrial, ovarian, germ cell, and paraneoplastic cancers.
Discussing Supplements With Doctors
Meanwhile, people are getting guidance on supplements from outside the clinic. The article cites a study published May 15, 2024, in Supportive Care in Cancer that surveyed 219 women from online support groups for people using scalp cooling to prevent cancer-related hair loss. That survey found that only 5% of people who responded spoke to a dermatologist about hair loss concerns though nearly 22% reported trying over-the-counter vitamins and supplements.
“Our work on online support groups for patients experiencing hair loss from cancer treatments suggests that many patients are starting supplements based on their own research and word-of-mouth recommendations,” Layna Mager, a medical student at the Ohio State University College of Medicine in Columbus who co-authored the report, says.
Yet it is critical, Mager says, for cancer patients to let their care teams know about any supplement use. “Biotin, along with many other over-the-counter supplements, are not widely regulated or studied with randomized clinical trials. Additionally, these studies rarely, if ever, include cancer patients, making it difficult to comment on side effects and efficiency in this patient population.”
Pieter Cohen, a primary care physician at Cambridge Health Alliance in Massachusetts, says that supplements should be taken with the same seriousness as prescriptions and other drugs.
In addition to speaking to their doctors about supplement use, people in treatment can get up-to-date information on products they are interested in from the National Institute of Health’s Office of Dietary Supplements, Cohen says. Information included in advertisements and on supplement bottles may not be reliable as it does not have to be proven in large-scale human studies, he says.
“The health claims on supplements can be completely separated from reality,” Cohen explains. Regulations prohibit supplement companies from making claims about treating, curing or preventing a disease, but they often get around these restrictions by using vague language that suggests benefits without a specific claim.
For example, people with cancer may be worried about getting infections. “You can’t sell a supplement and say it’ll treat an infection, that would be a disease claim,” Cohen says—but it is legal to say something like “this will support immune health.”
Hair loss supplements can use the same approach. “You couldn’t legally say this treats alopecia, but you could say this supplement maintains healthy hair,” Cohen says.
Safe Options for Cancer-related Hair Loss
People with cancer can safely use topical minoxidil, often sold under the brand name Rogaine, to support hair growth after completing treatment, the JCO Oncology Practice article notes.
“Topical minoxidil is a safe, affordable treatment for chemotherapy-induced alopecia that is available over the counter,” Mager says, noting that it typically takes about four to six months of regular use to see the effects. A scalp-cooling device, which can help prevent hair loss at the time of treatment, is another option, she adds.
Cancer survivors who are taking biotin supplements should stop taking the supplement before blood tests. “When taking biotin, lab checks of important hormone levels may be skewed, so it is important to hold biotin for at least 72 hours prior to any planned blood work,” Mager says.
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