When to Stop Biotin Before a Blood Test

If you're taking biotin supplements for hair, skin, or nail health, you might be surprised to learn that high doses can interfere with certain blood tests, causing misleading results that could potentially trigger a misdiagnosis or unnecessary treatment.

Indeed, stopping your biotin supplement at the correct time can make all the difference between “everything’s fine” and “something doesn’t look right here.”

Read on to learn how long it takes for biotin to leave your system and when to stop taking biotin before a blood test.

Biotin is also known as vitamin B7 or vitamin H (the H stands for “haar und haut,” German for “hair and skin”). 

It’s a water-soluble vitamin that helps your body convert food into energy. Biotin supports your metabolism, making sure fats, carbs, and proteins get broken down and put to good use.

While the easiest place to get biotin is from foods — like eggs, nuts, and bananas — your body actually produces it in small amounts as well.

So, unless you’re surviving on a strict diet of air and bad decisions, you’re probably getting enough. But here’s the twist: Biotin is everywhere in the supplement world, often in megadose amounts, which is where things get tricky. 

Why Do People Take Biotin Supplements?

Biotin supplements have a therapeutic place in certain health conditions, including multiple sclerosis (MS) and mitochondrial metabolic disorders. 

You’ve probably also come across them if you’ve ever typed “how to grow thicker hair” into a search bar. 

Biotin has built a reputation as the go-to vitamin for luscious hair, stronger nails, and glowing skin — the doses of which tend to be significantly higher than what’s used therapeutically for conditions such as MS. But there’s little evidence that it’s helpful unless perhaps you have an underlying biotin deficiency.

Keep in mind, though, that actual deficiency is rare, with most Americans eating around 35 to 70 micrograms (mcg) of biotin per day through their diet, which is twice the recommended amount needed to maintain good health.

Of course, this hasn’t stopped biotin from becoming the poster child for hair and beard growth supplements.

Men, in particular, often take biotin to combat thinning hair or to help grow a fuller beard. Some even believe it boosts their energy levels, though that’s more anecdotal than hard science.

If you’ve been popping biotin like candy in hopes of reaching peak hair and beard potential, you’re not alone. 

But before your next blood test, you might want to hit the pause button — turns out, too much of a good thing can really mess with your laboratory test results.

Biotin might be great for your hair and nails, but when it comes to blood tests, it’s like that one friend who always gives slightly misleading advice — confident, well-meaning, but ultimately potentially causing chaos.

Many lab tests use something called biotin-streptavidin technology to measure things like hormone levels, thyroid function, and heart health. 

The problem? If you’ve been taking high doses of biotin (especially those high-dose supplements marketed for hair and beard growth), your test results might be about as reliable as an “everything’s fine” text from the significant other who just stormed out on you.

Biotin’s interference with blood tests can go two ways:

• False highs. Some tests might show elevated biotin levels, making it look like you have a metabolic or hormonal surge when you really don’t.

• False lows. Other tests might show dangerously low levels, potentially leading your doctor to think you have thyroid issues, heart problems, or other medical mysteries.

This mix-up is especially risky when evaluating things like thyroid panels, heart health markers, and testosterone and other hormone tests. 

Research shows that even a single 10 milligram (10,000 mcg) dose of biotin can interfere with thyroid function tests conducted within 24 hours of taking the supplement. 

For example, a small study among six healthy adults taking 10,000 mcg of biotin per day for one week experienced lab interferences that could have drastic consequences. 

This led to falsely low levels of thyroid stimulating hormone (TSH), thyroxine (T4), or triiodothyronine (T3), which could lead to a thyroid disorder misdiagnosis, as well as low N-terminal pro-brain natriuretic peptide, which could lead to a missed diagnosis of congestive heart failure.

Basically, high-dose biotin can turn your blood work into a guessing game that could lead to potentially harmful presumptions about what’s going on in your body. 

So if you want to help ensure accurate lab results, it’s best to hit the pause button on biotin before your blood test.

Like vitamin C and the other B vitamins, biotin is water-soluble, meaning your body doesn’t store it — it just uses what it needs and flushes out the rest. 

But if you’ve been taking high-dose (like 5,000 to 10,000 mcg) supplements daily, it’s going to take some time for your system to clear out the excess.

On average, biotin has a circulating half-life of around two hours. This just means that half of it is out of your system at that time. Some research has found that extremely high 100 to 300 mg (100,000 to 300,000 mcg) doses have a half-life ranging from around eight to 19 hours.

How long it takes to get out of your system fully depends on things like your metabolism, your kidney function, and how much biotin you’ve been taking (and for how long). 

Now for the burning question: when to stop taking biotin before a blood test.

If you want your blood test results to be as accurate as possible (which you should), you’ll need to pause your biotin supplements before your test. 

Here’s the general rule: Most laboratories say biotin users should stop taking it at least 48 hours before their test to be safe. 

And if you accidentally pop a biotin pill the night before your test? Just be upfront with your healthcare provider and let them know. 

It’s better than getting a call saying your thyroid is out of control when really, it’s just your supplement playing tricks on the lab results.

Perhaps you’ve been taking biotin for beard growth or to keep your hair thick and nails strong. That’s all well and good — until you have a blood test scheduled. 

Here’s what to do to help make sure your lab tests are accurate:  

• Inform your provider. Before your blood test, let them know you take biotin and at what dose. They might recommend delaying the test or using a different method to avoid interference and false low or high levels.

• Take a pause on biotin supplements. If you’re taking biotin, stop at least 48 hours before your test.

• Check your other supplements. Biotin hides in unexpected places, like multivitamins (which often contain about 30 mcg of biotin), energy drinks, and even some protein powders. Scan the label and see if you’re getting extra biotin without realizing it.

• Follow up if lab test results seem off. If your blood work comes back looking suspiciously abnormal, and you forgot to mention your biotin intake, ask your provider if a retest is needed. It’s better than getting misdiagnosed for something you don’t have.

Do Food Sources Matter?

Short answer? Not really.

Biotin from food isn’t the problem — it’s the mega-doses of the nutrient from supplements that can mess with lab tests. 

The amount of biotin in natural sources like eggs, nuts, seeds, and avocados is much lower than what’s in high-dose pills. For example: 

• Eggs: 10 mcg per egg

• Canned salmon: 5 mcg per 3-ounce serving

• Sweet potato: 2.4 mcg per half cup cooked

Compare that to a 5,000-mcg supplement, and you can see why a handful of almonds won’t be the culprit behind false lab results. So, if you’re eating a normal diet, no need to stress.

Even the Food and Drug Administration (FDA) had to step in to wave a red flag about biotin messing with blood tests. 

In 2017, it issued a safety communication warning that high doses of biotin can cause misleading lab results — sometimes with serious consequences.

Why does this matter? Because doctors rely on lab tests to diagnose and treat conditions, and if your results are off due to biotin, you could end up with:

• A misdiagnosis, like thinking you have a thyroid problem when you don’t, or vice versa.

• Unnecessary treatments because your hormone levels appear abnormally high or low.

• A missed diagnosis, like a heart issue, going undetected because biotin masked the real results.

One of the biggest concerns is cardiac biomarker tests. These are used to check for heart attacks, and biotin interference could lead to falsely low results — meaning a real problem gets overlooked. That’s not just inconvenient; it’s potentially life-threatening.

Biotin may be your go-to for hair, skin, and nails, but when it comes to blood tests, it can be more of a troublemaker than a helper. If you’re taking biotin supplements — especially high doses — you’ll want to plan ahead to avoid inaccurate lab results. 

Here are the key takeaways for guys using biotin: 

• High doses require the most caution. This generally applies to supplemental doses of 5,000 to 10,000 micrograms, which are more likely to interfere with lab tests, leading to false highs or lows. This could result in misdiagnosis or unnecessary treatments.

• Stop taking biotin before a blood test. Usually, a window of at least 48 hours before your blood test is adequate to help ensure accurate results.

• Tell your healthcare professional. If biotin supplements are regular players in your healthcare routine, be sure to let your provider know. This helps them interpret your test results correctly, or they may even suggest alternative testing methods.

Don’t let your supplements skew your health data. Before your next blood test, talk to your provider about what you’re taking and plan to hit the pause button on biotin.