How Biotin Affects Your Thyroid Labs: And What You Can do to Prevent It



I’m sure you’ve heard of it. It’s the B vitamin that everyone takes to try to get thick hair, strong nails, and beautiful skin. I hope your locks are flowing and your skin is glowing! But, if you’re taking biotin in any amount, listen up!  Especially if you’re having routine lab tests done to monitor your thyroid function, and definitely if you’re using those lab results to evaluate how well your thyroid medication is working.

You don’t want anything messing around with your hopefully optimal TSH, T4, and the whole family of thyroid values, but there’s one nutrient that can mess things up a bit. A nutrient that can have a wild affect on your thyroid numbers. You guessed it...BIOTIN.

If you’re taking a multivitamin, a B-complex, or a prenatal vitamin, you need to look closely at the nutrients that are included. Biotin is probably in there, and it should be! But let’s talk about how biotin can make some thyroid values appear less (or more) than what they really are.


What is Biotin?

Biotin, also known as B7, is an essential and life-sustaining nutrient and not one to be feared. Many people take biotin to improve the integrity of their hair, nails, and skin. Biotin is also needed for metabolizing fatty acids and carbohydrates, encouraging cell growth, and combining amino acids to form larger protein structures. It does a lot!

It’s included regularly in B-complex, multi- and prenatal vitamins, and you only need about 30 micrograms a day to prevent deficiency, but most supplements have at least 500 mcg and up to a few thousand.

Some who take megadoses of biotin are getting 10,000-30,000 mcg per day!


Biotin and Your Thyroid

So what does taking biotin have to do with your thyroid?

Taking supplemental biotin can cause your TSH levels to read lower than they actually are and your T4 levels to read higher than they actually are. So, wherever your actual TSH is, taking a biotin supplement can make it appear lower and wherever your actual T4 level is, biotin supplementation can make it appear higher on your lab results. Let’s look at a few scenarios.

  • If your TSH is usually on the low end of normal, it would likely read below the normal range if you’re taking a biotin supplement. This could lead to a misdiagnosis of Grave’s disease.

  • If your TSH is on the high end of normal, biotin will push that down to the mid-normal range on your lab report.

  • If your TSH is actually high, biotin’s depressive effect could make it appear to still be within the normal range. A high TSH indicates hypothyroidism, and this very significant yet treatable condition would be missed if you’re taking a biotin supplement.

In a similar but opposite way, biotin supplementation can raise your T4 level, making it appear more adequate than it actually is. If your actual T4 level is too low, biotin will falsely make it appear more “normal.” It your T4 is on the high end or above normal, biotin can show this as even higher on your lab results. This, too, can result in a misdiagnosis of Grave’s disease or a missed diagnosis of hypothyroidism.

For those who are already on thyroid medications for hypothyroidism, these falsely manipulated values become even more important. Since you’re already working to keep your TSH down within optimal levels, taking a biotin supplement that falsely lowers your TSH result can make it appear that your medication is working better than it is. You’re also working to keep your T4 level up, and taking a biotin supplement can make it appear that it’s higher than it really is.

If you’re still struggling with frustrating symptoms but your TSH and T4 are “normal,” you better check your supplements to make sure biotin isn’t influencing your results.

To be clear, biotin does not harm or change the actual function of your thyroid. It just alters the results that are seen on a lab report. You can see how these inaccurate results can cause misdiagnoses of hypothyroidism or hyperthyroidism. And it goes without saying that receiving treatment for a condition you don’t have or not receiving proper treatment for one you do can be extremely dangerous!

This is yet another reason why your TSH should never be the only marker used to properly evaluate your thyroid function. Even when it appears to be “normal,” there can be outside factors preventing you from seeing what’s really going on. Will the real TSH please stand up?

You need to look at TSH within the whole spectrum of your thyroid hormones and antibodies so everything can be read in context with each other.


I’m Taking Biotin. What Should I Do?

Many women don’t think to tell their doctors they are taking biotin. It’s not a medication, and most women are encouraged to take a multi- or prenatal vitamin anyway, so it doesn’t register as something important to report to a physician. And honestly, many physicians might not know of the biotin-thyroid interaction, so they won’t be inclined to ask.

If you’re taking a multivitamin, B-complex, and especially if you’re taking an isolated biotin supplement, you don’t necessarily need to stop those unless your health practitioner recommends that for other health reasons.

To prevent biotin from giving you false readings for your TSH, T4 and potentially other thyroid numbers, simply stop your biotin-containing supplements for 3-5 days before your next thyroid labs are drawn. Always check with your health practitioner before stopping any supplement that he/she has recommended or that you have reservations about discontinuing, even for a short time.


What About Biotin From Foods?

Biotin that comes naturally from food sources won’t be enough to manipulate lab values. Foods highest in biotin include animal products like liver, meats, egg yolks, and salmon. Always try to opt for grass-fed, pasture-raised, and wild-caught varieties. Plant sources like nuts and seeds, avocado, and sweet potatoes also contain smaller amounts of biotin.


Many external factors can cause your otherwise “normal” lab values to appear out of range on paper, especially sensitive hormonal markers like your thyroid. Emotional and physical stressors, lack of sleep, certain medications, and even the time of day you have certain labs drawn can send some values up or down in the short term.

Now you know that even taking an essential vitamin can falsely influence a reading on your thyroid labs! Keep including your biotin, but consider holding off for a few days before your labs are drawn so your thyroid isn’t tested under the influence!


Now I want to hear from you!

Are you currently taking biotin…in a multi or as an isolated supplement?

Have you seen it interfere with your thyroid lab tests?

Do you suspect that this has happened without you knowing or realizing it?

Let me know!





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