Biotin Discontinuation Before Thyroid Function Testing
Biotin should be discontinued for at least 7 days before thyroid function testing to avoid interference with laboratory results.
Understanding Biotin Interference with Thyroid Tests
Biotin (Vitamin B7) can significantly interfere with thyroid function tests due to its interaction with the streptavidin-biotin chemistry used in many immunoassays. This interference can lead to:
- Falsely low TSH levels
- Falsely elevated free T4 and free T3 levels
- Incorrect diagnosis of hyperthyroidism or Graves' disease
Mechanism of Interference
Many laboratory tests for thyroid hormones use a streptavidin-biotin complex as part of their detection method. When a patient takes biotin supplements, the excess biotin in their blood competes with the biotin used in the assay, leading to inaccurate results 1, 2.
Recommended Discontinuation Period
Based on clinical evidence, biotin should be discontinued for specific periods before testing:
- Standard recommendation: 7 days before thyroid function testing 1
- Minimum period: 2-5 days for most laboratory assays 3
A case report demonstrated that thyroid function tests normalized after a patient withheld biotin for one week 1, confirming this timeframe is sufficient for accurate results.
Clinical Implications
Potential Misdiagnosis
Failure to recognize biotin interference can lead to:
- Misdiagnosis of hyperthyroidism in healthy individuals 4
- Inappropriate treatment with anti-thyroid medications 5
- Confusion in management of patients with existing thyroid conditions 4
Risk Factors for Interference
The degree of interference depends on:
- Biotin dosage: Higher doses (such as those used for MS treatment at 300mg/day) cause more significant interference 3
- Timing of last dose: The closer to testing, the greater the interference
- Laboratory assay type: Streptavidin-biotin based immunoassays are affected 2
Recommendations for Clinicians
- Always ask about biotin supplementation before ordering thyroid function tests
- Document biotin use in patient records, including dosage
- Advise patients to discontinue biotin for 7 days before scheduled thyroid testing
- Consider alternative testing methods (radioimmunoassay or mass spectrometry) if biotin cannot be discontinued 3
- Repeat testing if unexpected results occur and biotin use is subsequently discovered
Patient Education Points
- Inform patients that biotin is found in many supplements labeled for "hair, skin, and nail health"
- Explain that even OTC biotin supplements can affect test results 4
- Emphasize the importance of disclosing all supplements to healthcare providers
- Reassure patients that temporary discontinuation of biotin is safe
Special Considerations
For patients with multiple sclerosis on high-dose biotin therapy (typically 300mg/day), coordination between neurologists and endocrinologists is essential to plan appropriate testing intervals that minimize disruption to treatment while ensuring accurate thyroid assessment 3.
The FDA drug label for biotin specifically warns that "biotin levels higher than the recommended daily allowance may cause interference with some laboratory tests" and advises patients to inform healthcare providers about all supplements they take, including biotin 6.