Does biotin lower or raise Thyroid-Stimulating Hormone (TSH) levels on lab tests?

Biotin Interference with TSH Laboratory Testing

Biotin lowers TSH levels on laboratory tests when biotin-streptavidin based immunoassays are used, creating falsely decreased TSH values that can mimic hyperthyroidism. 1, 2

Mechanism of Interference

The direction of biotin interference depends entirely on the assay design:

• Sandwich (noncompetitive) assays: Biotin causes falsely decreased results by blocking streptavidin binding sites, which is the mechanism affecting TSH measurements 1
• Competitive assays: Biotin causes falsely elevated results by competing with biotinylated reagents 1
• TSH assays typically use sandwich immunoassay methodology, making them susceptible to falsely low TSH values in the presence of biotin 2

Clinical Evidence of TSH Suppression

Prospective human data confirms significant TSH lowering:

• In a study of 13 adults taking biotin 10 mg/day for 8 days, significant falsely decreased TSH measurements occurred when using the Roche Cobas 6000 platform (which uses biotin-streptavidin technology) 2
• Maximum interference occurred 2 hours after biotin ingestion on both day 1 and day 8 of supplementation 2
• TSH normalized when biotin was withheld for one week 3

Assay-Specific Vulnerability

Critical distinction between platforms:

• Biotin-based immunoassays (Roche Cobas 6000, Beckman DXI 800) show significant TSH interference with falsely low values 2, 4
• Non-biotin-based assays (Abbott Architect TSH assay, Alinity i analyzer) are not affected by biotin 4, 5
• The Beckman DXI 800 TSH assay specifically is not biotin-based and remains unaffected, while the same platform's FT3 and FT4 assays are affected 4, 5

Clinical Pattern Recognition

The hallmark pattern suggesting biotin interference:

• Elevated FT4 and FT3 with inappropriately normal or low TSH is biochemically inconsistent with primary hyperthyroidism 4
• This discordant pattern (suppressed TSH with elevated free hormones) should immediately trigger suspicion for biotin interference rather than true thyrotoxicosis 3, 6
• Physical examination showing no signs or symptoms of hyperthyroidism despite "laboratory thyrotoxicosis" is the key clinical clue 3

Dosing Threshold for Interference

Clinically relevant biotin doses:

• Interference occurs at 10 mg/day (approximately 333 times the recommended daily allowance of 30 mcg) 2
• High-dose biotin therapy for multiple sclerosis uses 10,000 times the RDI (300 mg/day), creating severe interference 3
• Even over-the-counter biotin supplements at 10 mg daily cause measurable interference 2

Critical Patient Populations at Risk

Patients requiring careful TSH monitoring:

• Thyroid cancer patients on levothyroxine suppression therapy, where accurate TSH measurement is essential for dose titration 2
• Multiple sclerosis patients on high-dose biotin (300 mg/day) for disease management 3, 6
• Patients with Graves' disease on antithyroid medication, where falsely low TSH may be misinterpreted as disease relapse 6

Practical Management Algorithm

When biotin interference is suspected:

1. Obtain detailed supplement history including all over-the-counter vitamins and hair/nail supplements that commonly contain biotin 7, 3
2. Withhold biotin for 48-72 hours (ideally one week) before repeat thyroid function testing 3
3. Contact the laboratory to determine if biotin-streptavidin methodology is used for TSH assays 3
4. Request alternative assay platforms that do not use biotin-streptavidin technology if available 5
5. Measure total T4 as a confirmatory test, since some total T4 assays are not biotin-based and will show normal values if biotin interference is present 4

Common Pitfall to Avoid

The most dangerous error is increasing antithyroid medication or initiating treatment for apparent hyperthyroidism based on falsely suppressed TSH values in patients taking biotin supplements, when the patient is actually biochemically euthyroid 3, 6. Always reconcile laboratory findings with clinical presentation before treatment changes.