Thyroid function tests are among the most commonly ordered blood panels. They are also among the most vulnerable to biotin interference. With 5000mcg of biotin in our formula, this is a topic we take seriously.
TSH (thyroid-stimulating hormone), free T4, free T3 and thyroid antibody tests commonly use streptavidin-biotin immunoassay platforms. Excess biotin in your blood can cause TSH to read falsely low and T4/T3 to read falsely high, mimicking hyperthyroidism.
A falsely low TSH combined with falsely high T4 could lead a doctor to diagnose hyperthyroidism in a patient who actually has normal thyroid function. This could trigger unnecessary treatment with anti-thyroid medication.
Some laboratories recommend discontinuing biotin supplements 48–72 hours before thyroid testing. Because biotin is water-soluble, blood levels decrease relatively quickly once supplementation stops. Always follow your specific lab's guidance.
We print the FDA biotin safety warning on every page of our website. We include it in our footer. We wrote this dedicated article. Some competitors do not even know their biotin dose, making this warning impossible for them to give accurately.