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How Does Biotin Affect A Thyroid Test

What Should You Do

How Biotin Interferes with Thyroid Lab Tests & Causes Falsely Elevated Results

As a thyroid patient, you should be acutely aware of the fact that biotin impacts your thyroid lab tests.

This is true even if you aren’t knowingly taking biotin.


Because only about 30% of people taking biotin realize that they are taking it .

Think about it.

How many supplements are you taking right now? Are you aware of the ingredients in every single one of those supplements?

Some supplements, such as the ones that I offer, contain upwards of 15 ingredients.

While the ingredients are not always at their maximum dose, they can still cause minor interference with testing assays and may impact your lab tests.

My recommendation to you, as a patient, is to be aware of everything that you are putting in your body.

Pay attention to your supplements and look for any extra biotin.

You should also have a knowledge of how biotin impacts your lab tests so that you can inform your doctor.

If a thyroid lab test comes back abnormal, and if you are taking any supplement, don’t automatically assume that the problem is your thyroid.

Think first about other factors such as the supplements you are taking, whether or not they contain biotin, and simply re-test in a few weeks.

This retesting phase may prevent a lot of unnecessary stress and changes to your thyroid medication .

Potential For Clinical Misdiagnosis

There are many erroneous biochemical diagnoses that may occur in patients taking high dosages of supplemental biotin.

Imagine, for example, a case in which lab results on a patient indicate elevated free thyroxine, elevated free triiodothyronine, elevated TSH receptor antibodies as well as a low TSH. A clinician would view this constellation of findings as indicative of possible Graves disease.

Alternatively, the same constellation of laboratory findings may be obtained for a euthyroid patient taking excessive biotin. Similarly, the laboratory findings for patients treated with testosterone replacement may show a false low or normal PSA levels in the presence of excess biotin supplementation.

Likewise, primary hyperparathyroidism would be difficult to diagnose in patients with hypercalcemia and falsely low PTH. It is of utmost importance to obtain a comprehensive history of biotin use when conducting an initial intake of all medications taken, and again before bloods are drawn to assess endocrine hormone levels to avoid the potential for misdiagnosing a patient without assurance that biotin is not a contributory factor to the results.

What About Biotin From Foods

Biotin that comes naturally from food sources wont be enough to manipulate lab values. Foods highest in biotin include animal products like liver, meats, egg yolks, and salmon. Always try to opt for grass-fed, pasture-raised, and wild-caught varieties. Plant sources like nuts and seeds, avocado, and sweet potatoes also contain smaller amounts of biotin.

Many external factors can cause your otherwise normal lab values to appear out of range on paper, especially sensitive hormonal markers like your thyroid. Emotional and physical stressors, lack of sleep, certain medications, and even the time of day you have certain labs drawn can send some values up or down in the short term.

Now you know that even taking an essential vitamin can falsely influence a reading on your thyroid labs! Keep including your biotin, but consider holding off for a few days before your labs are drawn so your thyroid isnt tested under the influence!

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Blog: Are You Taking Biotin

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Are you taking biotin?

It seems that, lately, I have been asking this question repeatedly to my clinic patients sometimes daily.

Last week, I saw a patient who follows with our endocrine clinic for a thyroid problem. For over 2 years, I have struggled with the interpretation of her thyroid function tests. I could not add up the lab results with her clinical status. She was asymptomatic, but her thyroid function tests have been abnormal.

Yes, I am, she answered.

When I asked her if she was taking biotin, she was kind of surprised, and I guess she had never been asked this question prior. At the same time, she acted as if she thought I was some kind of a genius to ask the question. I guess she may have thought to herself, wondering, How did the doctor know that I was taking biotin?

The rest of the dialogue went like something like this:

How long have you been on biotin? I asked.

For about 4 years, she replied.

And what strength? I asked.

Five mg daily, she replied.

But biotin is not listed on your medications list in the EMR, I said.

Oh, I am sorry, I did not realize it was a medication, she explained.

The medications are usually reviewed by our medical assistants at the check-in, and then by clinicians during the office visit. Clearly, we have missed this important piece in the patients medication history.

What Other Tests May Be Ordered In Addition To A Thyroid Panel


Blood tests that may be performed in addition to a thyroid panel may include:

  • Thyroid antibodies – to help diagnose autoimmune thyroid disease and distinguish it from other thyroid conditions
  • Calcitonin – to help diagnose C-cell hyperplasia and medullary thyroid cancer
  • Thyroglobulin – primarily to monitor treatment and recurrence of thyroid cancer
  • Thyroxine-binding globulin – to evaluate patients with abnormal T4 and T3 levels

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Impact Of Biotin On Immunoassays

An excess biotin intake may adversely effect immunoassays in two different ways:

  • In competitive immunoassays, excessive biotin is likely to produce a falsely high result
  • In immunometric, or sandwich assays, it may result in false low results.

For a list of common endocrine-related competitive and sandwich assays that may return inaccurate findings in the presence of biotin supplementation see Table 1.

Biotin Interference With Certain Lab Tests May Lead To Incorrect Test Results

Many lab tests use biotin technology due to its ability to bond with specific proteins which can be measured to detect certain health conditions. For example, biotin is used in hormone tests and tests for markers of cardiac health like troponin. Biotin, also known as vitamin B7, is a water-soluble vitamin often found in multi-vitamins, prenatal vitamins, and dietary supplements marketed for hair, skin, and nail growth.

Biotin in blood or other samples taken from patients who are ingesting high levels of biotin in dietary supplements can cause clinically significant incorrect lab test results. The FDA continues to see reports of adverse events, in addition to the one death reported prior to the 2017 safety communication, related to biotin interference with lab tests.

Incorrect test results may lead to inappropriate patient management or misdiagnosis. For example, a falsely low result for troponin, a clinically important biomarker to aid in the diagnosis of heart attacks, may lead to a missed diagnosis and potentially serious clinical implications. Prior to the 2017 safety communication, the FDA had received a report that one patient taking high levels of biotin died following low troponin test results when a troponin test subject to biotin interference was used.

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How Do I Prepare For My Lab Tests If I Take Biotin

Your healthcare practitioner may advise you to discontinue taking biotin supplements a few days before having lab tests done.

If you are prescribed biotin for medical reasons, you should follow the directions of your healthcare practitioner.

How quickly biotin is cleared from your body depends on factors such as the amount taken and the health of your kidneysbiotin is eliminated from the body through the kidneys. The level of biotin in the blood is highest about 1 to 3 hours after taking a dose. Biotin can affect your lab results for hours to days after taking a dose, depending on these factors.

How To Get Accurate Test Results

Impact of Biotin Interference on Thyroid Lab Testing

Talk to your doctor about any and all medications and vitamins youre taking. In the case of Biotin, its a water-soluble vitamin. That means if you stop taking it a week before your blood tests, it should be out of your system, allowing an accurate result. Once your testing is complete, you should be able to resume taking your vitamins. Be sure to ask your healthcare provider about appropriate dosage levels.

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How It Can Be Dangerous

For the most part, I think that the attention that biotin receives and how it impacts your thyroid lab tests is largely overblown.

But that doesn’t mean that there are some potential dangers associated with biotin use.

Perhaps the most concerning potential thing that could happen would be a misdiagnosis or a mischaracterization of thyroid status in the body upon tests which are influenced heavily with biotin interference.

This could theoretically become an issue which may cause both stress and anxiety for some patients.

How would this happen?

Well, remember that biotin interferes with the testing assay .

The interference tends to cause abnormally high readings of thyroid lab tests, especially high levels of both free T4 and free T3.

It would be plausible then, that doctors who are not very knowledgeable about biotin and how it influences your lab tests may make adjustments based off of these false readings .

For hypothyroid patients this is concerning because this population is often already undertreated, to begin with!

The last thing you would want to do is give your doctor another reason to reduce your dose of thyroid medication which is probably not high enough, to begin with.

If your doctor reduces your dose based on the false premise that your thyroid lab tests are elevated then you will most likely experience WORSENING symptoms of hypothyroidism.

That means things like more hair loss , more fatigue, more weight gain, and so on.

Biotin And Your Thyroid

So what does taking biotin have to do with your thyroid?

Taking supplemental biotin can cause your TSH levels to read lower than they actually are and your T4 levels to read higher than they actually are. So, wherever your actual TSH is, taking a biotin supplement can make it appear lower and wherever your actual T4 level is, biotin supplementation can make it appear higher on your lab results. Lets look at a few scenarios.

  • If your TSH is usually on the low end of normal, it would likely read below the normal range if youre taking a biotin supplement. This could lead to a misdiagnosis of Graves disease.
  • If your TSH is on the high end of normal, biotin will push that down to the mid-normal range on your lab report.
  • If your TSH is actually high, biotins depressive effect could make it appear to still be within the normal range. A high TSH indicates hypothyroidism, and this very significant yet treatable condition would be missed if youre taking a biotin supplement.

In a similar but opposite way, biotin supplementation can raise your T4 level, making it appear more adequate than it actually is. If your actual T4 level is too low, biotin will falsely make it appear more normal. It your T4 is on the high end or above normal, biotin can show this as even higher on your lab results. This, too, can result in a misdiagnosis of Graves disease or a missed diagnosis of hypothyroidism.

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Biotin Hair Products: Can They Affect Thyroid Tests

I was just wondering if using biotin shampoo and conditioner can affect thyroid tests ?

Welcome to Mayo Connect, a community of people living with a wide variety of diseases and conditions, who support each other along the way. We try to be informed medical consumers, and our own best advocates in our care. We are not medical professionals, so not able to provide medical advice. We can tell you what has worked for us and provide you with information and conversation about your questions.

May I ask what led you to Mayo Connect with such an interesting question? I love hearing these things, as they make me think and read. Your question led me to this article about biotin supplements and thyroid tests: which of course doesn’t address conditioners or other things you put on your body.

Here are some things to consider. The amount of biotin that is in shampoo or conditioner is really tiny compared to the 5-10mg of biotin that interferes with tests. What is put on hair only enters your body through scalp or skin, not the hair shaft so it’s really tiny in amount. Finally, biotin placed on your hair will not promote growth, as it does not enter your body through the hair shaft, which is essentially dead. So if your body is deficient in biotin, to promote hair growth you need to get it inside you, either through a healthy diet or a supplement.

Fda Warns That Biotin May Affect Some Lab Test Results

Factors That May Affect Your Thyroid Test Results

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

More and more people are taking biotin also known as vitamin B7 because they believe it will improve their hair, nails, and skin. The daily recommended intake for an adult is 30 micrograms , but many biotin supplements marketed for beauty reasons contain much higher doses, ranging from 5,000 µg to 10,000 µg. And some new studies even suggest that mega doses of biotin could be used to treat diseases, such as neurodegenerative disorders like multiple sclerosis.

But biotin may interfere with some laboratory testing, causing results of tests to be either falsely high or falsely low. These inaccurate test results can cause healthcare practitioners to misdiagnose and mistreat their patients.

Excess biotin in patients blood samples can interfere with types of tests called immunoassays because many use biotin as part of the testing methodology. For example, some immunoassays use biotin to bind chemicals and other substances in the blood to the test tube so they can be measured. Excess biotin in the blood from supplements can block that binding and the substance wont be measured accurately.

The FDA urges the general public to that know that biotin is found in many over-the-counter supplements in levels that may interfere with laboratory tests. Examples include:

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Need For More Assertive Interaction With Patients

Clinicians are cautioned to act decisively given the risk of inaccurate or missed diagnosis and in light of the urgency that prompted a Food and Drug Administration Safety Communication on this very topic.

The FDA recommends1 that clinicians take the following precautions:

  • Talk to your patients about any biotin supplements they may be taking, including supplements marketed for hair, skin, and nail growth
  • Be aware that many lab tests, including but not limited to cardiovascular diagnostic tests and hormone tests, that use biotin technology are potentially affected, and incorrect test results may be generated if there is biotin in the patients specimen
  • Communicate to the lab conducting the testing if your patient is taking biotin
  • If a lab test result doesnt match the clinical presentation of your patient, consider biotin interference as a possible source of error
  • Know that biotin is found in multivitamins, including prenatal multivitamins, biotin supplements, and dietary supplements for hair, skin, and nail growth in levels that may interfere with lab tests
  • Report to the lab test manufacturer and the FDA if you become aware of a patient experiencing an adverse event following potentially incorrect laboratory test results due to biotin interference.

For specific directives in the FDA Safety Communication, go to: FDA.

Reviewbest Practices In Mitigating The Risk Of Biotin Interference With Laboratory Testing

Increased use of high-dose biotin raises concerns about immunoassay interference.

Patients and physicians may be unaware of the presence of biotin in supplements.

Biotin interference thresholds vary by assay and by manufacturer.

Education of patients, physicians, and laboratory staff will increase awareness.

Best practice guidance is needed to prevent, detect, and manage biotin interference.

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Biotin Lab Test Interference

It has been well documented that biotin supplementation can interfere with several laboratory tests, not just tests involving the thyroid. Most studies note that small doses of biotin aren’t likely to significantly affect lab values, but it is certainly a possibility with high doses .

There are several theories as to why biotin can affect lab tests :

  • Biotin may block test assay signals, leading to falsely elevated test results.
  • Biotin may compete with biotin-containing complexes the test utilizes, which can lead to falsely low results.

Exactly which lab tests are potentially affected by biotin, and by what extent, isn’t well known and evidence suggests that there may even be variability from test to test or with tests from different manufacturers.

In November 2017, the FDA released a safety communication warning about biotin supplementation and lab tests:


Biotin Pills And Supplements

Biotin affecting thyroid readings? What is the best test for biotin? And more biotin answers!

Biotin is an ingredient in many over-the-counter multivitamin pills and nutritional supplements and has specific uses in the medical field. It is recommended that pregnant women take prenatal vitamins that contain biotin for healthy fetal development. Additionally, high doses of biotin have been prescribed for some health conditions, such as biotinidase deficiency and some types of alopecia . Some new studies suggest that mega doses of biotin could be used to treat nervous system disorders like multiple sclerosis. Because some specialists who treat MS patients expect approval from the FDA soon, they are already prescribing these mega doses for their patients. More recently, biotin has been promoted for hair, skin, and nail health. More and more consumers are taking high doses of biotin for these benefits, particularly because there is no evidence that biotin is harmful to your body.

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