Researched and written by Curl Centric. Read by an AI voice.
Biotin helps your hair when you're actually low in it, and that's rare. We go through what the research tested, what's in the bottle, and why high doses can throw off your blood tests.
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The full guide, with every source: Biotin for hair growth.
One-page printable of biotin's daily amounts by age and life stage: https://www.curlcentric.com/wp-content/uploads/2026/09/curl-centric-biotin-intake-levels.pdf
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Your hair is already growing. The problem is keeping it.
On average, hair grows a third to half an inch a month, and curlier hair tends to grow more slowly. If your length looks stuck, that’s your hair breaking off as fast as it grows in. Here are the seven causes of breakage and the weekly routine that stops them.
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Transcript
This is Curl Science by Curl Centric.
If you've ever stood in the vitamin aisle holding a bottle of hair gummies for your edges or your length, you've probably seen biotin on the label. It might be the most popular hair growth supplement there is. So we went looking for the research showing that biotin grows hair. In this episode, we'll tell you who it actually helps, what it can do to your blood tests, and what will do more for your length.
Let's start with what biotin is. Biotin is vitamin B7. Your body uses it to turn the food you eat into energy. You get it from everyday foods like eggs, salmon, sunflower seeds, sweet potatoes, and almonds.
Your body needs very little of it. The daily amount set for adults is about 30 micrograms. A microgram is one millionth of a gram, so that's a tiny amount. Most people already get 35 to 70 micrograms a day from food alone.
So where does the idea that biotin grows hair come from? It starts with something true. When people are seriously low in biotin, their hair can thin and fall out. When they take biotin, it can grow back.
But a true biotin deficiency is rare. The National Institutes of Health says severe deficiency has never been reported in a healthy person eating a normal diet. It usually has a specific cause. That includes a rare inherited condition usually caught through newborn screening, eating a lot of raw egg whites, taking certain seizure medicines for a long time, and heavy drinking.
It also looks like more than thinning hair. People with a true deficiency often get a scaly red rash around the eyes, nose, and mouth, along with brittle nails and pink eye. So if your hair is thinning on its own, with none of those signs and none of those causes, that's not what biotin deficiency usually looks like.
In 2017, a team of dermatologists reviewed every published case where biotin helped someone's hair or nails. They found 18. In all 18, the person had an underlying condition, like an inherited enzyme problem or a rare hair disorder. None of them was a healthy adult. The reviewers concluded there wasn't enough evidence to recommend biotin for healthy people.
What about people without a confirmed deficiency? An older placebo-controlled trial was published in 1966. Twenty-eight women with thinning hair took 10 milligrams of biotin a day, and 18 took a placebo, which is a pill with nothing active in it. After four weeks, there was no difference in hair growth between the two groups. Four weeks is short, so that trial can't settle the question on its own.
Then in 2024, researchers measured hair growth in 10 healthy men. Before biotin, their hair grew 2.50 millimeters a week. After two weeks of 5 milligrams a day, it grew 2.47 millimeters a week. That's essentially no change. This study was also small and short, but it gives us no sign that extra biotin speeds up hair growth in healthy people.
So why do so many people swear biotin worked for them? One reason is timing. A lot of sudden shedding starts a few months after a major event, like having a baby, running a high fever, having surgery, or going through a stressful stretch. Once the trigger has passed, many people regain their usual fullness within six to nine months. If you started biotin while you were shedding, it can look like the biotin fixed it when your hair was already on its way back.
Before we get to the practical part, one quick ask. If this is the kind of answer you want, follow the show, so the next one reaches you.
Now let's talk about how much biotin is in those bottles. Remember, the daily amount set for adults is about 30 micrograms. Many hair gummies contain 2,500 to 6,000 micrograms per serving. That's 83 to 200 times that amount. Single biotin pills often come in 5,000 or 10,000 micrograms, and one 10,000-microgram pill holds almost a year's worth of the daily amount.
Biotin hasn't been linked to the kind of classic vitamin toxicity you may be worried about. In one large study, people with multiple sclerosis took 300 milligrams a day, and their overall side effects were about the same as those reported by people taking a placebo. But that doesn't mean taking large doses is harmless.
The biggest concern has nothing to do with your hair. High doses of biotin can make some blood tests give the wrong answer. Many lab tests use biotin as part of how they measure things, so extra biotin in your blood can throw off the result.
The Food and Drug Administration has warned about this since 2017. One of the biggest concerns is a test called troponin, which doctors use to check for a heart attack. Biotin can make that test read falsely low, which could make a heart attack harder to detect. The FDA has continued to receive reports involving this type of interference.
Biotin can also affect some thyroid tests. According to the National Institutes of Health, even a single 10-milligram dose can change certain thyroid test results within hours. And here's the part that surprised us. If you see a dermatologist about hair loss, they may order blood tests to check your thyroid and your hormones. The biotin you took for your hair can interfere with the very tests meant to find out why you're losing it.
So if you take biotin, tell your doctor, and tell whoever orders your bloodwork. Check your labels, too. Biotin shows up in hair, skin, and nails gummies and in some prenatal vitamins, and the name on the bottle doesn't always tell you.
When does biotin make sense? The American Academy of Dermatology says to take it only when a blood test shows you're low. If your levels are normal, they don't recommend it.
So here's the honest answer. Biotin helps your hair when you're actually low in it, and that's rare. For everyone else, the research doesn't show that it makes your hair grow faster, thicker, or longer.
For many curly girls, what stands between you and more visible length isn't a missing vitamin. It's breakage. A study of more than a thousand South African schoolchildren found that combed natural hair appeared to settle at a steady length within about a year after a haircut. The researchers concluded that breakage was likely catching up with new growth. Your hair is already growing. Holding on to that length is where most of the difference is.
If your hair is thinning, your part is getting wider, or you've been shedding more than usual for a few months, see a dermatologist. Thinning and shedding have many possible causes, and a dermatologist can help you identify yours.
Keeping your length is what this whole show is about, so we wrote a free guide on it. It walks you through the seven most common causes of breakage and a weekly routine that helps you reduce it. You can get it at curlcentric.com/keep-the-length, and the link is in the show notes.
That's it for this episode. If it helped, follow Curl Science in your podcast app so the next one reaches you, and leave us a rating while you're there. Curl Science is researched and written by the Curl Centric team, and it's read by an AI voice.
