Biotin: How It Acts in the Body (and Why Everyone Thought It Was the Solution)

By Vanessa Manfredini | Biomedical Scientist and future Nutritionist

Have you ever bought that little bottle of biotin thinking your hair would stop falling out? 💊 I've had that doubt too, and I suspect if it came up for me, it came up for many people. So today I'm going to tell you what this vitamin really does in your body, where all this fame came from, and a warning that almost no one gives. Come with me! 🌿

"Biotin is not a lie. What was exaggerated was the promise built upon it."

First: what is biotin 🧬

Biotin is a B-complex vitamin, also called vitamin B7 (you might find it as B8 or vitamin H on older labels). It is water-soluble, meaning it dissolves in water. This means the body doesn't store large amounts of it, and excess is usually eliminated through urine.

How it acts in the body 🔬

Here's the part I love, because it explains everything. Biotin doesn't act alone: it functions as a coenzyme, a kind of fitting piece that some enzymes need to work.

Without this piece, a group of enzymes called carboxylases simply don't function properly. And what do these enzymes do? They participate in the metabolism of all three macronutrients: carbohydrates, fats, and proteins. In other words, biotin is involved in converting food into energy and in building things in the body.

So where did the fame come from? 🕵️‍♀️

This is the question I wanted to answer, because the story is quite interesting and explains a lot.

First, it came from veterinary medicine. Decades ago, it was observed that animals with cracked and brittle hooves, such as horses and pigs, improved with biotin supplementation. Hooves are also keratin. The mental leap was immediate: if it works for hooves, it must work for nails and hair.

Then came the cases of actual deficiency. In people who truly lacked biotin, hair loss, brittle nails, and skin changes were among the symptoms. And, by replenishing the vitamin, these symptoms improved. But here lies the detail that changed everything.

Marketing took a truth (biotin solves problems when biotin is lacking) and turned it into a universal promise (biotin makes hair grow). It's the same old recipe. 😅

And the detail that shatters the promise 🤔

Biotin deficiency is rare. And for two very good reasons:

In other words: if you don't have a deficiency, taking more probably won't transform your hair. The body simply eliminates the excess.

A curiosity I love 🥚

Raw egg white contains a protein called avidin, which binds to biotin in the intestine and prevents its absorption. Therefore, frequent consumption of raw egg white (that old trend of blending egg whites) is one of the few known ways to cause deficiency in healthy people.

The good news? Heat deactivates avidin. Boiled, scrambled, or fried eggs don't have this problem. Another reason not to eat raw eggs! 🍳

Now the serious warning: biotin interferes with your lab tests ⚠️

This is the point that I, as a Biomedical Scientist, make a point of discussing, because almost no one knows about it, and the consequences can be serious.

Many laboratory tests use a technology called immunoassay, and several of them specifically use the biotin-streptavidin system to function. When there's too much biotin circulating in the blood, it interferes with the test reading. The result can be falsely high or falsely low, depending on the test.

International regulatory bodies have already issued official warnings about this. This is not for you to panic or to stop anything on your own: it's for you to inform. Tell your doctor and the lab that you take biotin. If it's necessary to pause before a test, the professional will tell you. 💚

What if I already take biotin and need lab tests? ⏱️

This is the practical question almost no one answers, so let's address it. The good news is that biotin leaves the blood quickly: its half-life is about two hours. The recommended pause time varies depending on the dose you take.

Two details make a difference. First: those with kidney issues eliminate biotin more slowly and may need more time. Second: biotin hides in unexpected places, such as multivitamins, energy drinks, and even some whey protein, especially those that come with a vitamin mix. It's worth reading the labels of everything you take. 🔍

After the collection, you can return to normal. And even if you've paused, inform the lab: each equipment has a different sensitivity, and they know which of their tests are affected. A single sentence from you can prevent a wrong result. 💚

If your hair is falling out, the path is different 🌱

Hair loss is almost never a lack of biotin. It's usually something else, which is why investigating is much more valuable than buying a little bottle:

And there are causes that don't always show up in tests: postpartum, surgery, a severe infection, a period of intense stress, or a very restrictive diet can cause hair loss a few months later. The body has memory. 💚

And is there seasonal hair loss? 🍂

Yes, there is, and this information calms many people. A study that followed over 800 healthy women for six years observed that the proportion of hair strands in the resting phase increases in the summer. Since this phase lasts about three months, hair loss usually appears later, in the fall.

In other words: if every year, around the same time, you notice more strands in the drain, this might be the natural hair cycle, not a problem. But pay attention, this is not a reason to ignore it: if the hair loss is intense, lasts a long time, or is accompanied by other symptoms, it's still worth investigating. 💚

So biotin is useless? 💚

It is very useful! It's essential for the body to function, and supplementation makes total sense for those with a proven deficiency or a specific condition, always with professional guidance.

What isn't supported is the promise of transformed hair for those who already have enough biotin. And, honestly, that's even good news: it means you probably don't need to spend money on another bottle. 🌿

"Before buying the bottle, it's worth finding out what your body is trying to tell you."

Have you ever taken biotin expecting a miracle? 💚

Tell me in the comments! And share with that friend who has the bottle in hand right now. 🌹