Biotin Supplements Alter Thyroid Test Results

Today I’m sharing an important tidbit that I just learned a few years ago.  Probably I learned it once many decades ago, but really, I don’t think this is a commonly known fact.  So now, my 3000+ readers, I’m commissioning you to share this knowledge with your family and friends.

First let’s talk a little bit about Biotin.  Biotin (Vitamin B7) is the vitamin that is most recommended for hair and nail growth.  It is available over the counter in hundreds of products.  The Recommended Daily Allowance (RDA) for biotin is 30mcg (micrograms).  Most multivitamins do not contain the RDA, so often patients who are having trouble with their hair or nails will seek out a separate biotin or “hair and nail” supplement.  Biotin is a water-soluble vitamin, so any excess is excreted in the urine, and super high doses of biotin essentially make expensive bright yellow pee.  Despite its widespread use and recommendation, there is little actual scientific evidence that biotin is effective outside of true biotin deficiency which is rare.  It is, however, safe, and inexpensive and anecdotally effective, so I generally take an “it won’t hurt” position. Because biotin “strengthens” hair it will take at least six months to see a noticeable change in the hair.  It is important to note that biotin WILL NOT affect the hair cycle like Rogaine to encourage actual hair growth.  

But, Biotin does have one downside.  It interferes with testing for Thyroid function.  Why does that matter?  Most patients who are having trouble with their hair or nails start a Biotin vitamin at the advice of family and friends, and often they don’t mention this to their doctor.  Then, after seeing little response from their Biotin vitamin they come to the doctor and request that their thyroid be checked.  Why the thyroid?  Thyroid function can affect both the strength and growth of hair and nails.  It’s a reasonable request.  Here’s the problem… 

A thyroid blood test is inaccurate if a patient is consuming Biotin vitamins.

What?  You heard me correctly.  Biotin supplementation can lead to falsely HIGH levels of T3 and T4 AND falsely LOW levels of TSH.  In essence, this means that you could have low thyroid function and biotin makes it look fine when it is not.  

The American Thyroid Association recommends stopping Biotin for at least 2 days prior to getting thyroid blood tests for most accurate results. 

In scientific studies the dose of biotin noted to interfere was a dose of 5mg (or 5000mcg) per day or more.  Note, the RDA is 30mcg, but many supplements are in those upper ranges.  If you are seeing your doctor, please always inform of any supplements you are taking as they may interfere with laboratory tests and medication that may be prescribed.  

Hope this helps and please share with your friends!  To learn more about subjects like this, check out the articles below.

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