February 01, 2021

Can vitamin B-7 (biotin) supplementation interfere with medical tests?

Q: I needed to get a blood test to check my thyroid, and my doctor asked if I take biotin, saying the supplement could interfere with the result. Can biotin supplements interfere with other medical tests?

A: Yes, biotin supplements can affect thyroid tests and other medical lab tests and produce inaccurate results. That's why it's important to let your health care provider know if you are taking it. Biotin, or vitamin B-7, is often in multivitamin supplements and in supplements advertised to enhance hair, nail and skin health, though these claims have limited evidence.

It's recommended that you ingest 0.03 milligrams (mg) — or 30 micrograms (mcg) — of biotin a day, which you can obtain from foods such as eggs, fish, seeds, sweet potatoes and spinach. Some multivitamins have about this much biotin, but some supplements can contain 5 to 10 mg — enough to potentially affect lab tests. Some lab tests rely on an interaction between biotin and certain test proteins. High amounts of biotin in your blood can interfere with this.

While reports of biotin interference have focused on thyroid tests, biotin can also affect troponin tests — which are important to diagnose a heart attack. Biotin may also interfere with measures of testosterone, progesterone, folate and iron stores (ferritin) and many other tests.

The amount of biotin it takes to affect a test varies. There's no standard recommendation as to how long before these tests you should stop taking biotin to ensure accurate results.

For most situations, stopping biotin supplementation for 12 to 24 hours is likely to be sufficient. However, in people who take very high amounts — or in people with kidney problems — persistently elevated biotin concentrations can occur. Stopping supplementation three...