Many immunoassays use a biotin–streptavidin step. Patients taking high-dose biotin supplements, often sold for hair and nails, can have falsely high or falsely low results depending on assay design — including thyroid hormones, troponin and some reproductive hormones.
A pattern that does not fit the clinical picture, such as raised free T4 with suppressed TSH in a well patient, should prompt a supplement history.
- Ask about hair, skin and nail supplements when immunoassay results do not fit the patient
- Check whether your platform's assays are biotin-sensitive
- Suggest a repeat sample after a biotin-free interval where results are discordant
- Add a comment to discordant thyroid reports flagging possible interference
Why it matters
Biotin interference can mimic hyperthyroidism or mask a raised troponin, leading to wrong treatment.
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