Can a hair, skin or nail supplement affect my lab results?

Yes. Some supplements contain biotin, which can interfere with certain laboratory tests, including some hormone and thyroid tests. That can make a result misleading without reflecting a true change in your health. Not every test is affected. NIH biotin information.

This is one reason MedFIT asks about supplements as well as prescriptions. A product marketed for hair or nails still belongs on the list.

Do not assume one stopping interval applies to every product and test. The instructions depend on what you take and what is being measured.

Next: Share the product label with MedFIT before your blood draw and ask whether any preparation is needed.