From the Research
Biotin supplements should be stopped at least 72 hours before thyroid function tests, including TSH measurements, to avoid interference with test results. Biotin can artificially lower TSH levels and falsely elevate T3 and T4 levels, potentially leading to misdiagnosis of thyroid conditions, as seen in a case report where a patient's thyroid function tests normalized after withholding biotin for a week 1. This interference occurs because many laboratory immunoassays use biotin-streptavidin binding technology, and excess biotin in the blood can disrupt these testing mechanisms. The effect is dose-dependent, with higher biotin doses (such as those used for hair and nail supplements, typically 5-10 mg daily) causing more significant interference than the lower doses found in multivitamins (usually 30-60 mcg) 2, 3.
Some key points to consider:
- Biotin interference can lead to inaccurate thyroid function test results, including TSH, free T3, free T4, total T3, and total T4 levels 2
- The interference can be significant, with one study showing that a daily dose of 10 mg of biotin can cause falsely lower TSH levels and falsely elevated T3 and T4 levels 2
- The duration of biotin interference can vary, with one study showing that 5 mg/d of biotin can interfere with thyroid function tests for up to 8 hours, while 10 mg/d can interfere for up to 2 days 3
- It is essential to inform healthcare providers about biotin supplement use before thyroid testing, as they may recommend temporarily discontinuing biotin or using alternative testing methods that are not affected by biotin 4, 5
In clinical practice, it is crucial to prioritize the patient's safety and well-being by avoiding potential misdiagnosis and inappropriate treatment adjustments due to biotin interference. Therefore, stopping biotin supplements at least 72 hours before thyroid function tests is a reasonable and evidence-based recommendation to ensure accurate test results and optimal patient care.