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How Does Biotin Affect Thyroid Tests

Laboratory Interference In The Thyroid Function Test

How Biotin Interferes with Thyroid Lab Tests & Causes Falsely Elevated Results
  • Department of Endocrinology, Diabetes, and Isotope Therapy, Wroclaw Medical University, Wroclaw, Poland
  • Department of Forensic Medicine, Wroclaw Medical University, Wroclaw, Poland
  • open access


    Thyroid hormones and thyroid-stimulating hormone laboratory tests are commonly used worldwide, and their results have an important influence on decisions about treatment and further diagnostic processes.

    Any discrepancies between symptoms and laboratory results or between results of different tests should be closely investigated to avoid misdiagnosis and unnecessary treatment.

    Inconsistencies in hormone tests might be a result of physiological changes in hormonal balance, a disease, drug intake, or laboratory interference. Major factors that interfere with thyroid function tests are: heterophilic antibodies, macro TSH, biotin, thyroid hormones autoantibodies, anti-streptavidin, and anti-ruthenium antibodies.

    In this paper we discuss the influence of different factors on the procedures of hormonal immunoassays, as well as methods to minimise the risk of false results and misdiagnoses.


    Thyroid hormones and thyroid-stimulating hormone laboratory tests are commonly used worldwide, and their results have an important influence on decisions about treatment and further diagnostic processes.

    Any discrepancies between symptoms and laboratory results or between results of different tests should be closely investigated to avoid misdiagnosis and unnecessary treatment.

    Full Text:

    Biotin Pills And Supplements

    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.

    Medications Affecting The Thyroid Test

    Common preparations, over the counter drugs, and minerals may affect your thyroid test and your thyroid health. Common medications that affect thyroid and antibody blood tests are:

    • lithium: thyroid antibodies have been found with intake of lithium. Lithium is concentrated in the gland and interferes with thyroid hormone synthesis/release and an increase in thyrotropin levels.
    • estrogen and estrogen-containing birth control pills: interferes with total T4 and total T3 measurements.
    • heroin and methadone hydrochloride: interferes with total T4 and total T3 measurements.
    • dopamine agonists: suppress thyrotropin levels to lower-than-normal values. Thyrotropin is undetectable in patients with true hyperthyroidism.
    • nonsteroidal anti-inflammatory drugs: displace thyroid hormones from thyroid-binding globulin, increase FT4 and FT3 concentrations and depress thyrotropin levels.
    • androgens: interferes with total T4 and total T3 measurements.
    • iodides: are hidden in many preprations and non-prescription drugs can induce iodide hypothyroidism and goiter.
    • anabolic steroids: interferes with total T4 and total T3 measurements.
    • nicotinic acid: interferes with total T4 and total T3 measurements.
    • glucocorticoids: interferes with total T4 and total T3 measurements.
    • beta blockers and corticosteroids: minimally inhibit the peripheral conversion of T4 to T3.

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    What Do My Thyroid Test Results Mean

    The two most common types of thyroid function tests are the T4 and TSH test. Typically, these two tests are ordered together.

    The T4 testmore commonly known as the thyroxine testis used to determine if your thyroid is overactive. If this is the case, you will be diagnosed with hyperthyroidism.

    Symptoms of hyperthyroidism include unplanned weight loss, tremors, diarrhea and anxiety.

    The TSH test will reveal how much thyroid-stimulating hormone is in your blood. Normal levels range from 0.4 to 4.0 milli-international units of hormone per liter of blood.

    If youve been diagnosed with hyperthyroidism and your TSH levels are above 2.0 mIU/L, you are at a heightened risk of developing hypothyroidism, which can result in weight gain, fatigue, depression and weak hair and nails.

    If your doctor believes you have hyperthyroidism, he or she may order a T3 test to check for levels of the hormone triiodothyronine.

    This hormone level should be within 100-200 nanograms of hormone per deciliter of blood. If your levels are abnormally high, it is possible that you are suffering from an autoimmune disorder called Graves disease.

    The final thyroid function test your doctor may order is the T3 resin uptake test. Also known as a T3RU, this blood test will measure the binding capacity of a hormone called thyroxin-binding globulin.

    Your doctors office should reach out to you within a matter of days to walk you through the results of your thyroid test.

    When Is It Ordered


    A thyroid panel may be ordered when you have signs and symptoms that suggest underactive thyroid or overactive thyroid due to a thyroid disorder.

    Signs and symptoms of an underactive thyroid may include:

  • Slowed heart rate
    • Trouble tolerating heat
    • Sometimes more frequent bowel movements
    • Some uncommon problems that can affect the eyes: puffiness around the eyes, dryness, irritation, excessive tearing, light sensitivity, blurry double vision
    • In some cases, bulging of the eyes
    • Less frequent or lighter menstrual periods in women

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    How Is The Test Used

    A thyroid panel may be used to evaluate thyroid function and/or help diagnose thyroid disorders.

    Typically, the preferred initial test for thyroid disorders is a TSH test. If the TSH level is abnormal, it will usually be followed up with a test for free T4. Sometimes a total T3 or free T3 will also be performed. Often, the laboratory will do this follow-up testing automatically. This is known as reflex testing and it saves the healthcare practitioner time from having to wait for the results of the initial test and then requesting additional testing to confirm or clarify a diagnosis. Reflex tests are typically performed on the original sample that was submitted when the initial test was requested.

    As an alternative, a thyroid panel may be requested by your healthcare practitioner. This means that all three tests will be performed at the same time to get a more complete initial picture of thyroid function.

    Magnetic Resonance Imaging Scan

    MRI scans use magnets instead of radiation to create detailed cross-sectional images of your body. MRI can be used to look for cancer in the thyroid, or cancer that has spread to nearby or distant parts of the body. But ultrasound is usually the first choice for looking at the thyroid. MRI can provide very detailed images of soft tissues such as the thyroid gland. MRI scans are also very helpful in looking at the brain and spinal cord.

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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.

    Hair Loss Biotin And Thyroid Patients

    Biotin and your thyroid tests

    Can you, or should you, take biotin as a thyroid patient?

    We’ve been discussing how biotin can impact your lab tests but we haven’t really discussed why thyroid patients are likely to be taking this nutrient.

    The reason is simple:

    Biotin plays an important role in the hair growth cycle and MANY thyroid patients suffer from hair loss, even when taking thyroid medication.

    And, as it turns out, this is probably, at least partially, related to the micronutrient status in their body.

    Biotin, an important vitamin, is one of many important vitamins and co-factors which are required for normal hair growth.

    If you are deficient in any of these nutrients then you may experience hair loss, hair fall, or hair which is slow to grow.

    All of these are big issues for thyroid patients who also tend to suffer from under-treatment of their own thyroid medication which is itself another risk factor for hair loss.

    Hypothyroidism also predisposes people to develop micronutrient deficiencies because of the important role that it plays on your stomach.

    Low thyroid levels can impact micronutrient absorption and increase your risk for developing gut-related issues such as IBS or SIBO.

    In addition, patients with Hashimoto’s also have a higher risk of developing Celiac disease which can also limit the absorption of macromolecules and micronutrients.

    All of these factors can potentially impact your hair growth.

    It’s no wonder why, then, that many thyroid patients look to biotin for help.

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    What To Do In Preparation For A Thyroid Blood Test

    While it would seem to make sense to abstain from any not-so-great habits before having a thyroid blood test, it is probably best to assess your thyroid under normal conditions for you. If you drink alcohol each day, it is best not to alter that pattern if you plan to continue drinking this amount after your test.

    You want to stick with your regular habits because you need to understand how your thyroid functions in your everyday life. Of course, you also need to let your doctor know how much you drink on average each day or week so they can take that into account when reviewing your labs.

    Aside from alcohol, several other factors can also skew your thyroid lab results. For example, the time of day you take your labs may have subtle influences on your thyroid labs, which can be problematic if you have subclinical hypothyroidism and are working with your thyroid doctor to decide if you need treatment.

    Also, women who are not menopausal may experience subtle shifts in their thyroid hormones depending on where they are in their cycle.

    To avoid discrepancies between current and past lab results, it is advisable that each time you test your thyroid, test around the same time of day, in the same phase of your menstrual cycle, and follow your usual daily habits.

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    What Is A Normal Thyroid Level

    Tests often used to assess thyroid hormone status include TSH and FT4 tests. The normal value for a laboratory test is determined by measuring the hormone in a large population of healthy individuals and finding the normal reference range. Normal ranges for thyroid tests may vary slightly among different laboratories, and typical ranges for common tests are given below.

    TSH normal values are 0.5 to 5.0 mIU/L. Pregnancy, a history of thyroid cancer, history of pituitary gland disease, and older age are some situations when TSH is optimally maintained in different range as guided by an endocrinologist.

    FT4 normal values are 0.7 to 1.9ng/dL. Individuals taking medications that modify thyroid hormone metabolism and those with a history of thyroid cancer or pituitary disease may be optimally managed with a different normal FT4 range.

    Total T4 and Total T3 levels measure bound and free thyroid hormone in the blood. These levels are influenced by many factors that affect protein levels in the body, including medications, sex hormones, and liver disease. A normal Total T4 level in adults ranges from 5.0 to 12.0g/dL. A normal Total T3 level in adults ranges from 80-220 ng/dL.

    Free T3 assays are often unreliable and not routinely used to assess thyroid function.

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    Recommendations For Lab Test Manufacturers And Developers

    • If your assay uses biotin technology, contact the FDA to discuss biotin interference.
    • Investigate interference from biotin in your assays that use biotin technology. Determine the lowest concentration of biotin that may cause clinically significant interference with your test.
    • Communicate with your customers if they may be unaware that your test uses biotin technology and how it may be affected.
    • Contact the FDA if you have any questions about biotin technology and interference.

    Fda Warns That Biotin May Affect Some Lab Test Results

    075: Why Biotin Can Mess Up Your Labs (Big Time)

    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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    Why Do I Need A Tsh Test

    You may need a TSH test if you have symptoms of too much thyroid hormone in your blood , or too little thyroid hormone .

    Symptoms of hyperthyroidism, also known as overactive thyroid, include:

    Symptoms of hypothyroidism, also known as underactive thyroid, include:

    • Weight gain
    • Low tolerance for cold temperatures
    • Irregular menstrual periods

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    Hypothyroidism is such a common condition especially affecting middle-aged females. When looking for answers of why females are developing more and more thyroid problems it has been seen the environmental factors can play an important role in this.

    Various environmental factors that can affect thyroid include diet, iodine consumption, stress, medications and supplements

    There are several supplements for various health conditions in the market and more people are trying to support their overall health through supplements.

    It is good to use supplements to support your health, but I always caution my patients that not all supplements are good for all conditions, plus the supplements might not be high quality and might be contaminated with substances which can actually harm your body.

    So its always best to discuss the supplements with a healthcare provider who is well versed with your medical history and can recommend the right supplements for you.

    Because the thyroid imbalance is such a common condition lot of my patients want to support their thyroid health with supplements but sometimes they are actually doing more harm than benefit to their thyroid.

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    How Can Health Care Practitioners Prepare Patients For Testing

    The FDA advises health care practitioners to ask their patients if they are taking any biotin supplements and inform the testing laboratory if interference from biotin is a possibility. They should also consider biotin interference as a potential reason for lab results not matching with a patients signs and symptoms and/or suspected health condition.

    I Was Advised To Refrain From Taking Biotin Before My Test But Forgot And Took A Dose The Day Of My Test What Should I Do

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

    You should tell your health care practitioner so that he or she can interpret your results correctly. Your health care practitioner can consider the possibility that biotin was the cause if one or more of your test results dont seem to make sense. You can also tell the person who draws your blood sample, so the information can be relayed to the testing laboratory.

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    What Are We Testing

    This is the first question. Some doctors only test TSH and gauge thyroid function from that. For me, TSH is a start, but it does not give me the whole picture. I like to test what the clinicians in the study used: free T3 and free T4 in addition to TSH.

    That said, many doctors order a thyroid panel consisting of TSH with total T4 and T3 uptake , and a calculated T7 index. This gives some information to interpret the TSH value, but it is not complete.

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    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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