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Can biotin throw off thyroid test?

Biotin, also known as vitamin B7, is a water-soluble B vitamin that plays an important role in metabolism. It is found naturally in many foods such as eggs, milk, salmon, and whole grains. Biotin supplements have become increasingly popular in recent years, often taken to improve hair, skin, and nail health.

However, there is some evidence that high doses of biotin supplements can interfere with certain lab tests, including thyroid tests. This has raised concern among both healthcare providers and patients about whether biotin is safe to take when thyroid testing is needed.

In this article, we will explore the current research on biotin and thyroid testing to answer the key question: Can biotin throw off thyroid test results? We will cover:

  • How biotin works in the body
  • The link between biotin and thyroid lab tests
  • Studies investigating the effects of biotin on thyroid tests
  • Proposed mechanisms for biotin interference
  • Recommendations for biotin use around thyroid testing

Understanding whether high-dose biotin supplements can disrupt thyroid tests is important for managing thyroid conditions. Accurate test results are critical for determining the right treatment.

How Biotin Works in the Body

Biotin acts as a coenzyme for several carboxylase enzymes involved in critical metabolic pathways:

  • Gluconeogenesis – the creation of glucose molecules from non-carbohydrate sources
  • Fatty acid synthesis – the production of fatty acids
  • Amino acid catabolism – the breakdown of amino acids

By supporting these pathways, biotin aids in:

  • Converting food into usable energy
  • Producing and metabolizing fats
  • Regulating blood sugar levels

The recommended daily intake of biotin is:

  • 30 mcg in infants
  • 35 mcg in children ages 4-8
  • 25 mcg in children ages 9-13
  • 30 mcg in teens ages 14-18
  • 30 mcg in adults over 18
  • 35 mcg in breastfeeding women

Most people obtain enough biotin through a regular diet. Biotin deficiency is rare, but can cause symptoms like hair loss, dermatitis, depression, and numbness or tingling in the extremities.

While biotin deficiency is uncommon, biotin supplements have become a popular dietary supplement, with claims to improve hair, nails, skin, energy levels, blood sugar control, and more. Doses in supplements often range from 30 mcg to 10,000 mcg (10 mg) or higher per day.

Biotin and Thyroid Function Tests

Thyroid function tests are done through blood tests that measure levels of thyroid hormones. The main ones are:

  • TSH (thyroid-stimulating hormone)
  • T4 (thyroxine)
  • T3 (triiodothyronine)
  • Thyroid antibodies such as TPO (thyroid peroxidase antibody)

Abnormal thyroid lab results may indicate thyroid conditions like hypothyroidism or hyperthyroidism. Therefore, accurate test results are critical for proper diagnosis and treatment.

Some studies have suggested that high levels of biotin in the blood can interfere with certain thyroid lab tests, causing falsely high or low results. But how significant is this risk, and should biotin supplements be stopped before thyroid testing?

Research on Effects of Biotin on Thyroid Tests

Several studies have investigated whether high-dose biotin supplements can interfere with thyroid function tests:

Early Small Studies

Some of the earliest evidence came from small studies:

– A 2016 case report on 2 patients found that taking 10-20 mg per day of biotin distorted test results for TSH, T4, and T3. The interference resolved after the supplements were stopped.

– In 2017, another small study in 11 patients reported biotin doses over 5 mg/day could elevate TSH levels and lower T4 levels on lab tests.

– However, a 2018 study in 7 patients taking 5-20 mg/day of biotin found no meaningful impact on thyroid labs.

Larger Retrospective Analyses

Larger retrospective analyses of thyroid lab results have provided more insight:

– A 2018 study examined results from nearly 600 patients. Biotin use was associated with abnormal TSH levels in 45% of cases and abnormal T4 levels in 60% of cases.

– In 2019, a study reviewed records from over 300,000 patients. Biotin use was linked to abnormal TSH results in 0.43% of patients and abnormal T4 results in 0.90% of patients.

– Another 2019 analysis of 78,000+ cases found biotin supplementation increased the risk of false positive hypothyroidism screening results.

Intervention Studies

To further determine the effects of biotin, a few interventional studies have been conducted:

– A 2018 controlled study in 18 patients found that taking 10 mg/day of biotin for a week reduced T4 levels and elevated TSH levels on lab tests compared to baseline.

– However, in a 2021 double-blind placebo-controlled trial in 32 patients, taking either 10 mg or 20 mg per day of biotin for 4 weeks did not alter TSH or T4 levels relative to placebo.

In summary, the majority of analyses suggest that high-dose biotin supplementation (usually 10 mg/day or more) can potentially interfere with thyroid lab test results in some people. However, the likelihood, degree of interference, and underlying mechanisms remain unclear.

Proposed Mechanisms

Researchers have proposed a few mechanisms for how excess biotin could interfere with lab tests:

Analytical Interference

Most thyroid lab tests use biotin-streptavidin technology. Since biotin and streptavidin have a strong affinity, high biotin levels in the blood sample may outcompete test analytes for binding sites. This can give falsely high or low readings.

Effects on Thyroid Hormones

High doses of biotin may influence thyroid hormone levels through effects on gene expression. In one study, 10 mg/day of biotin altered expression of 179 genes, including some linked to thyroid hormone metabolism.

Individual Factors

The effects of biotin on lab results may depend on individual factors like:

  • Dose and duration of biotin supplementation
  • Lab testing methodologies used
  • Individual differences in metabolism and clearance
  • Whether an individual has an existing thyroid condition

More research is still needed to better understand the mechanisms behind biotin interference in thyroid testing.

Recommendations for Biotin and Thyroid Testing

Based on the current evidence, here are some recommendations regarding high-dose biotin supplementation and thyroid testing:

For Patients

– Inform your doctor about any biotin supplements you are taking, including dose and frequency.

– Consider stopping biotin supplements at least 1-2 days before thyroid testing.

– If your doctor is concerned about possible interference, request a re-test after holding biotin for at least 1 week.

– Be aware biotin in multivitamins or B-complex likely does not cause interference at low doses under 5 mg per day.

For Healthcare Providers

– Ask patients about use of biotin supplements when ordering thyroid lab tests.

– Have patients discontinue biotin prior to testing if feasible.

– Re-test any abnormal thyroid results in patients taking biotin.

– Use an assay method like LC-MS/MS if possible, as it eliminates biotin interference.

For Lab Companies

– Implement protocols to detect and reduce biotin interference.

– Make clients aware of biotin’s potential to distort results.

– Develop and validate biotin-free assays.


In conclusion, there is evidence that high doses of biotin supplementation can interfere with some thyroid lab test results like TSH and T4 levels. However, the likelihood and degree of interference is still uncertain. Discontinuing biotin supplements 1-2 days before testing can help prevent possible distortion in results. More research is warranted on the effects of biotin on thyroid testing methodology and actual thyroid status. Until definitive guidelines exist, open communication between patients, healthcare providers, and laboratories regarding biotin use is advised to ensure accurate interpretation of thyroid testing.