Biotin is a B vitamin found in many hair, skin and nail supplements, often in amounts far above the daily value. The U.S. Food and Drug Administration has warned that, at high levels, it can interfere with certain laboratory tests. If you take a high-biotin supplement, tell your healthcare professional or laboratory provider before any blood test.
Can biotin affect blood test results?
Yes. High amounts of biotin, common in hair, skin and nail supplements, can affect the results of some blood tests. Many lab tests use biotin in their chemistry, so extra biotin in a sample can make results falsely high or falsely low, including some thyroid and troponin tests. If you take biotin, tell your healthcare professional or lab before testing.
Why biotin can interfere with some lab tests
This sounds strange at first. Why would a vitamin you swallowed change what a lab machine reads?
The answer is in how many modern tests are built. A large group of tests, called immunoassays, use a pairing of biotin and a protein called streptavidin as a kind of molecular glue: biotin is attached to one part of the test, streptavidin to another, and the two lock together tightly. That bond helps the test capture and measure a specific substance in your blood.
Now add a lot of free biotin to the sample. It competes for those streptavidin binding spots. Depending on how a particular test is designed, that competition can push a result falsely low or falsely high. Nothing is wrong with the test itself; it's reacting to extra biotin it wasn't designed to expect.
Typical daily intakes of biotin from food are small. The concern is with supplements that provide many times the daily value.
Which tests can be affected
Not every test uses biotin, and labs and manufacturers differ. Tests that have been reported as susceptible include:
- Thyroid tests, including TSH, free T4 and free T3. The American Thyroid Association notes that biotin most commonly causes falsely high T4 and T3 and falsely low TSH, which can lead to a wrong diagnosis of an overactive thyroid.
- Troponin, a test used to help evaluate the heart. The FDA has specifically flagged falsely low troponin results.
- Some hormone tests, such as certain reproductive and other hormone immunoassays.
- 25-hydroxyvitamin D, the usual vitamin D blood test, in some assays.
- Other immunoassays that use biotin–streptavidin technology.
Your lab will know which of its tests are affected. You don't need to.
How much biotin does it take?
There isn't one cutoff that applies to every test. The NIH Office of Dietary Supplements notes that people who regularly take more than 5,000 mcg of biotin a day may have enough in their blood to interfere with some immunoassays. It also notes that even a single 10 mg (10,000 mcg) dose has interfered with thyroid function tests performed within 24 hours.
A small 2017 study in JAMA shows what this looks like in practice. Six healthy adults took 10 mg of biotin a day for seven days. When the researchers ran the same blood samples through a range of hormone and non-hormone tests, a number of the biotin-based tests gave altered results while participants were taking biotin. It was a small study with no placebo group, but it's often cited because 10 mg is a common amount in over-the-counter hair, skin and nail supplements.
Lab technology is also changing. The FDA has noted that some test developers have reduced biotin interference in their tests, while others have not. That's useful progress, but you can't tell from the outside which test your lab is running, which is why telling them still matters.
What the FDA has said
On November 28, 2017, the FDA issued a safety communication warning that biotin can significantly interfere with certain lab tests and cause incorrect results that may go undetected.
On November 5, 2019, the FDA issued an updated safety communication with recommendations for consumers, healthcare providers, laboratories and test developers. The FDA has said it continued to receive adverse event reports in which biotin interference caused falsely low troponin results, and it publishes a list of troponin tests that haven't yet addressed the risk.
The FDA's industry guidance on biotin interference also points out where biotin turns up: in multivitamins, prenatal vitamins and supplements marketed for hair, skin and nail growth.
What to do before a blood test
The safest step is simple: tell your healthcare professional or the laboratory that you take a high-biotin supplement, and follow their instructions for that test.
It helps to have three details ready:
- The product name, including multivitamins (biotin is often in them).
- The amount of biotin per serving, from the Supplement Facts panel.
- When you last took it.
Some medical organizations have published their own guidance. The American Thyroid Association, for example, has advised patients to stop taking biotin for at least two days before thyroid testing. The right approach can depend on the test, your dose and your situation, so ask the person ordering the test rather than deciding on your own, and don't stop any prescribed medication without guidance.
If you're ever being assessed for chest pain or another urgent symptom, mention biotin to the care team even if it feels like a small detail.
How much biotin is in hair supplements?
The FDA's daily value for biotin is 30 micrograms (mcg). Supplements marketed for hair, skin and nails often contain much more: amounts of 5,000 mcg and 10,000 mcg are common.
Our hair supplement with 10,000 mcg biotin, Nutriveska Women's Hair Growth Support, contains 10,000 mcg of biotin per 2-capsule serving, alongside Saw Palmetto Extract, MSM, Ashwagandha Extract, Horsetail Extract, Bamboo Extract, zinc, vitamins D3, C and B6, and folate. That's why the product page includes a lab-test note, and why we wrote this article.
Biotin supports normal keratin production as part of a balanced diet.* Being open about the dose is part of our quality standards.
FAQ
Can biotin cause false thyroid test results?
Yes, it can. Thyroid immunoassays (such as TSH and free T4) are among the tests reported to be affected. Tell your healthcare professional or lab that you take biotin before testing.
Does biotin affect troponin tests?
Some troponin tests can be affected, and the FDA has warned that biotin may cause falsely low troponin results.
How long before a blood test should I stop biotin?
Ask the healthcare professional ordering the test. The American Thyroid Association has advised stopping biotin at least two days before thyroid testing, but guidance can vary by test.
Do hair vitamins contain enough biotin to matter?
Many do. Hair, skin and nail supplements often contain thousands of micrograms of biotin, well above the 30 mcg daily value. The NIH Office of Dietary Supplements notes that regular intakes above 5,000 mcg a day may interfere with some lab tests.
Should I stop taking biotin?
Not necessarily. The key is that your healthcare provider and lab know you take it, especially before blood work.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for general information and is not medical advice.
Sources
- U.S. Food and Drug Administration. Biotin Interference with Troponin Lab Tests – Assays Subject to Biotin Interference.
- U.S. Food and Drug Administration. Testing for Biotin Interference in In Vitro Diagnostic Devices: Guidance for Industry (references the Nov 28, 2017 and Nov 5, 2019 Safety Communications).
- American Thyroid Association. Clinical Thyroidology for the Public, Vol. 11, Issue 12 (December 2018): biotin and thyroid testing.
- NIH Office of Dietary Supplements. Biotin: Fact Sheet for Health Professionals.
- Li D, et al. Association of biotin ingestion with performance of hormone and nonhormone assays in healthy adults. JAMA. 2017;318(12):1150–1160.
