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Biotin and Thyroid Testing: Does high-dose supplementation change blood levels?

Biotin and Thyroid Testing: whats the fuss?

Back in 2016, a paper was released which showed abnormal thyroid results in a cohort of young patients. All six enrolled in the study were taking high doses of biotin as a result of a metabolic disorder. It was found that their T3 and T4 levels were measured as higher than they actually were, while TSH was recorded as lower than the real figure.

The researchers quickly linked the the biotin intake to the distortion in results; after all, there had been several researchers that had highlighted a potential problem. While the potential for biotin supplementation to interfere with certain tests was first theorized back in the early 90s (ref), it took some time for these issues to be reported ‘on the frontline’. Isolated case studies dripped in (ref, ref), and then, in 2012, a lone researcher took a whopping 30mg of Biotin and demonstrated important distortions in his thyroid markers (ref).

The problem hinges on the way that laboratories use a molecule called streptavidin to bind antibodies to the metabolite being measured. This works when the metabolites are ‘biotinylated’, as streptavidin has a strong affinity for biotin. If there is more Biotin than normal, there exists a risk that more binding will occur and the test will over-read (this can happen on low-molecular weight molecules, such as T3, T4, thyroid antibodies and cortisol). However, when measuring high-molecular weight molecules, such as TSH or PTH, a ‘sandwich’ assay is performed which follows a different process; in this instance, excessive biotin ends up holding the metabolite back from binding with the antibody and can therefore cause an innacurately low measurement (ref).

Potential consequences

The main concern is that, in individuals taking Biotin, two outcomes may occur:

– individuals with normal thyroid function will be considered to have Graves disease, and treated with thyroid suppression

– individuals with low thyroid function will be inaccurately judged to be ‘totally normal’

How much of a concern is this?

As the research was reported, an general alarmism could be found on the thyroid forums. “If you ever took Biotin and got normal thyroid results, consider yourself hypothyroid until proved otherwise,” became the received wisdom. Hobbytritionists weighed in on their blogs, warning that even the moderate amounts in multivitamins ‘must’ be stopped ahead of testing to avoid confusing the results.

As this wave of worry gathered steam, the one inconsistency was the fact that the lab results I was getting back remained so consistent. And, given that most individuals I work with have oxalate issues and I recommend high-dose Biotin for most of them, this raised questions as to whether the ‘biotin = inaccurate test’ equation was accurate.

Luckily, Canadian medics went one step further to help answer these questions (ref). They ran a study on 1,944 patients visiting the emergency department for tests, with 42% taking a biotin-containing multivitamin and 8% taking higher-dose Biotin supplements (a total of 812 subjects supplement. Their research took away the guesswork by measuring the amount of Biotin being taken by the patients and, crucially, their blood levels. The paper tells us that:

– the lowest blood concentration at which thyroid results were affected was 10ng/ml

– of the 812 patients taking Biotin, only 7.4% achieved this blood concentration

– although they did not link individual intakes to individual blood levels, 8.1% of the patients were taking 10,000mcg (which was the highest reported intake), so there is a strong connection between these particularly high doses and achieving threshold blood levels (although there were more patients taking these high doses than there was those crossing the threshold)


We can make several conclusion from this recent research:

– it is categorically not the case that ‘biotin supplementation = inaccurate results’

– 93.6% of individuals taking Biotin do not achieve blood levels to risk invalidating the test results

– de that there are at least some people who are capable of taking 10,000mcg of Biotin per day and not reaching the minimum threshold for disturbed measurements, although the near mirror-image between these groups indicates that individuals taking 10,000mcg per day are at risk of disturbed measurements

– 5,000mcg per day is probably not enough to risk disturbed measurements in most people (although we will need further investigation to confirm the exact relationships

My recommendation for testing

I often run thyroid tests and, in almost all cases, I will be testing both T3 and Reverse T3. As similar molecules (low molecular weight), both are subject to artificially over-reading should blood levels of Biotin reach sufficiently high levels. Therefore, measuring both does not just provide the practitioner with a more complete picture of what is happening in the thyroid system, it can also allow for complete confidence in the results we get back (after all, if T3 is low and Reverse T3 are high, then Biotin cannot push one down and push another up, which gives us an added assurance of reliable results).

As an anecdotal aside, I have assessed many tests in individuals taking Biotin at 5,000mcg and many tests in those not taking any Biotin. I have done so regularly for many years and I am yet to come across a test result that I find suspicious (deemed as either one that a) does not correlate with clinical symptoms and temperatures or b) one that does not correlate with responses to appropriate support).

The take home message is clear: Biotin can definitely distort the results, but this is not a common thing and can only occur at particularly high intakes (and even then, not in anyone). I am happy to run thyroid testing on individuals taking 5,000mcg per day, but would ensure that both T3 and Reverse T3 are measured for additional reliability.



Leave a comment

  1. How high is the biotin dose recommended for oxalate issues?

    1. There is no one-size-fits-all although 5000mcg per day is the most common dose.

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