Biotin in Multivitamins Can Significantly Interfere with Thyroid and Other Hormone Tests
Yes, biotin present in multivitamins interferes with thyroid function tests and numerous other hormone assays that use biotin-streptavidin technology, causing potentially dangerous misdiagnoses. The interference mechanism depends on assay design: competitive assays show falsely elevated results while sandwich assays show falsely decreased results 1, 2.
Mechanism of Interference
Biotin interferes specifically with immunoassays utilizing biotin-streptavidin binding technology 3, 1. The direction of interference is predictable based on assay format:
- Competitive assays: Excess biotin competes with biotinylated reagents, causing falsely elevated (false-positive) results 1
- Sandwich assays: Excess biotin blocks streptavidin binding sites, causing falsely decreased (false-negative) results 1
Thyroid Function Tests Affected
Biotin interference in thyroid testing is well-documented and clinically significant:
- TSH (sandwich assay): Falsely decreased, mimicking hyperthyroidism 4, 5
- Free T4 (competitive assay): Falsely elevated 4, 5
- Free T3 (competitive assay): Falsely elevated 4, 5
- Total T3: Falsely elevated on certain platforms (Roche Cobas 6000) 4
- Thyroglobulin: Falsely decreased on Siemens IMMULITE 2000 4
A prospective study demonstrated that even 10 mg daily biotin (far less than high-dose supplements) caused significant interference, with maximal effects occurring 2 hours post-ingestion 4. This creates a pattern mimicking Graves' disease or factitious hyperthyroidism when patients are clinically euthyroid 5, 6.
Other Critical Tests Affected
Beyond thyroid tests, biotin interferes with multiple clinically important assays:
- Cardiac troponin: Falsely decreased values, representing the most dangerous clinical scenario as this can lead to missed myocardial infarction diagnosis 1, 2
- Vitamin D (25-hydroxyvitamin D): Falsely elevated 3, 7
- Parathyroid hormone (PTH): Can be affected depending on assay platform 8, 7
The FDA drug label explicitly warns that biotin levels higher than the recommended daily allowance may cause interference with cardiovascular diagnostic tests (including troponin) and hormone tests 2.
Clinical Pitfalls and How to Avoid Them
The most dangerous scenario is falsely low cardiac troponin in acute coronary syndrome, which can result in missed myocardial infarction 1. When thyroid tests show biochemical hyperthyroidism but clinical examination is inconsistent with thyrotoxicosis, immediately suspect biotin interference 5.
Key clinical considerations:
- Multivitamins typically contain 30-300 mcg biotin, but interference occurs even at 10 mg daily 4
- High-dose biotin (10,000 times the RDI) is increasingly used for multiple sclerosis and cosmetic purposes 6
- Interference resolves rapidly after biotin discontinuation—faster than would be expected from T4 half-life alone 6
- Maximum interference occurs approximately 2 hours after biotin ingestion 4
Platform-Specific Vulnerabilities
Not all assay platforms are equally affected 4:
- Roche Cobas 6000: Significant interference with TSH, free T4, and total T3 4
- Siemens IMMULITE 2000: Interference with thyroglobulin and TBG 4
- Abbott Architect: Less susceptible to biotin interference 4
- LC-MS/MS: Not affected by biotin as it doesn't use biotin-streptavidin technology 4
Practical Management Algorithm
When encountering discordant laboratory results:
- Obtain detailed supplement history, specifically asking about biotin, multivitamins, hair/nail supplements, and multiple sclerosis treatments 2, 6
- Discontinue biotin for 48-72 hours before repeat testing 4, 7
- Consider alternative testing methods such as LC-MS/MS for thyroid hormones, which are not susceptible to biotin interference 4
- Verify assay platform with your laboratory to determine if biotin-streptavidin technology is used 1
Special Populations
In patients with end-stage renal disease on hemodialysis, biotin can cause dramatic swings in both 25(OH)D (from 25 to >100 ng/mL) and iPTH (from 966 to 63 pg/mL), which could adversely affect metabolic bone disease management 7. Thyroid cancer patients requiring careful levothyroxine titration are particularly vulnerable to erroneous TSH and thyroglobulin results 4.