Biotin and Lab Interference: The FDA Safety Warning

What was issued, and when

FDA released its safety communication on 28 November 2017, addressed to the public, health care providers, lab personnel, and lab test developers. A rise in reported adverse events prompted it, including one death.

An update followed on 5 November 2019, with a narrower message: some assay developers had redesigned their tests to blunt the interference, some had not, and reports of falsely low troponin results kept arriving.

Alongside the update, FDA published a standing page listing troponin assay devices subject to biotin interference where the risk hadn't been addressed. The list exists because the effect depends on the specific test your lab runs, not on anything visible from the outside.

How a vitamin breaks an assay

Nothing happens in the patient here. The trouble starts once the sample is in the tube.

Many immunoassays exploit the extremely strong binding between biotin and streptavidin, using it to anchor what is being measured. When a specimen carries a lot of free biotin, it occupies the streptavidin sites the assay depends on, and the signal stops reflecting what is in the blood.

The direction of the error depends on architecture. The AACC guidance puts it plainly: tests using streptavidin-biotin binding are subject to positive interference in biotinylated competitive immunoassays and negative interference in noncompetitive ones, usually called sandwich assays.

That's why one specimen can read too high on one analyser and too low on another. Troponin assays commonly use the sandwich format, so excess biotin there tends to push the result downward.

The test categories named

FDA published no exhaustive catalogue, and said so. The communication warns that many lab tests, including but not limited to cardiovascular diagnostic tests and hormone tests, that use biotin technology are potentially affected. The NIH fact sheet adds the common examples: assays measuring hormones such as thyroid hormone, and analytes such as 25-hydroxyvitamin D, can produce results that look falsely normal or falsely abnormal.

Troponin is where FDA concentrated its warnings, because a falsely low value carries immediate consequences. Thyroid testing is where the published case reports cluster.

What the reports looked like

The NIH fact sheet describes a recurring pattern: several case reports described findings falsely indicating Graves' disease and severe hyperthyroidism in patients taking 10 to 300 mg of biotin per day, including six children receiving 2 to 15 mg/kg body weight per day for inherited metabolic diseases.

Small deliberate studies show the same at lower exposures. Even a single 10 mg dose interfered with thyroid function tests administered within 24 hours. In six healthy adults given 10 mg a day for a week, several assays were affected, including falsely low thyroid stimulating hormone and falsely low NT-proBNP, a heart failure marker.

Ten mg is 10,000 mcg, well inside the range of ordinary hair and skin products. It surprises people because the recommended intake is nowhere near it.

On troponin specifically, FDA reported one patient death following a falsely low troponin result from an assay known to be subject to biotin interference.

The doses involved

FDA's figure for typical exposure is 0.03 mg per day, and the agency states that amount does not typically cause interference.

Above that, the numbers get large fast. FDA said it was aware of many supplements containing 20 mg of biotin and some containing up to 100 mg per pill, sometimes with directions to take multiple pills daily, and noted that physicians may recommend up to 300 mg per day for conditions such as multiple sclerosis.

Authorities differ at the bottom of the range. Germany's Federal Institute for Risk Assessment concluded that falsely altered results have been observed at various doses but mostly at intakes of 150 µg per day or more, and recommends a warning statement on supplements for anyone facing a lab test. There is no agreed single threshold, consistent with the laboratory guidance finding that interference concentrations vary by test and by manufacturer.

How often this actually happens

It is worth separating the mechanism, which is solid, from the frequency, which is contested.

Mumma and colleagues measured biotin in two large US cohorts. Of 797 emergency department samples from patients with suspected acute coronary syndrome, one came back above 20.0 ng/mL, which is 0.13 percent. Of 2,023 random laboratory samples, 15 exceeded that level, or 0.74 percent. Modeled risk of misclassifying a heart attack came out at 0.026 percent and 0.025 percent respectively, falling below 0.00001 percent by 6 hours.

The authors concluded interference has minimal impact on that assay's clinical utility. An editorial alongside the paper noted earlier work placed the share of emergency department patients above a lower threshold considerably higher, and that biotin measurements aren't standardised between studies.

What the agencies tell patients to do

This section paraphrases official guidance rather than issuing any.

FDA's recommendation to consumers is to talk with their doctor when taking or considering biotin, and to be aware that it appears in multivitamins, prenatal multivitamins, biotin supplements, and supplements marketed for hair, skin, and nail growth, sometimes at levels that interfere. The agency adds that some products contain high biotin amounts that aren't clear from the name.

On stopping before a blood draw, FDA's position is notably cautious: sufficient information isn't available to know whether stopping biotin for any number of hours before testing prevents incorrect results. If a result is already in hand and concerning, FDA advises asking the health care provider about the possibility of interference.

To providers, FDA's advice is to ask about supplements containing biotin, to assume many tests using biotin technology may be affected, to tell the performing laboratory, and to weigh interference whenever a result doesn't match the clinical picture. The AACC guidance adds that biotin clears relatively fast, so a follow-up specimen can often settle it.

Whether to hold a supplement before a blood draw is a decision for whoever ordered the test.

Frequently asked questions

Is biotin itself dangerous?

The concern FDA raised isn't toxicity, it's measurement accuracy. Nothing in the communication turns on biotin harming the person taking it.

Which of my blood tests could be affected?

You can't tell from the outside, and neither can this page. FDA named cardiovascular diagnostic tests and hormone tests while saying the list isn't exhaustive, and the AACC guidance states thresholds vary by test and manufacturer.

Should I stop taking biotin before blood work?

FDA doesn't give a withdrawal window, stating there isn't enough information to know whether stopping for a set number of hours prevents wrong results. Raise it with whoever ordered the test rather than deciding alone.

How much biotin does it take?

Reported cases range widely. The NIH fact sheet cites interference after a single 10 mg dose, and case reports spanning 10 to 300 mg per day, while 0.03 mg is the intake FDA mentions as typically not causing problems.

Why would a supplement interfere with a test at all?

Because a great many immunoassays are built on streptavidin-biotin chemistry. Biotin already in the specimen competes with the assay's own biotinylated components for the same binding sites.

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This article is for general information only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure, or prevent any disease. Talk with your health care provider before using biotin or stopping it before a scheduled blood test, especially if you take prescription medication.

Sources

• FDA Safety Communication, UPDATE: The FDA Warns that Biotin May Interfere with Lab Tests
• FDA, Troponin assays subject to biotin interference
• NIH Office of Dietary Supplements, Biotin Fact Sheet for Health Professionals
• Li et al., AACC Guidance Document on Biotin Interference in Laboratory Tests, J Appl Lab Med 2020
• Mumma et al., Biotin interference with a cardiac troponin T assay, Clin Chem Lab Med 2020
• BfR, Biotin supplements can interfere with laboratory tests