Derms Say This Popular Hair Supplement Is Actually a Nail-Health Hero

Thanks to the internet, biotin, or vitamin B7, has become synonymous with hair health. It's found in hundreds of supplements that claim to grow, strengthen, and thicken fine, fragile hair. But what if I told you that's not always accurate? (I know...shocker.) As board-certified dermatologist Sejal Shah, MD, FAAD, puts it, the evidence is weak. "Biotin is essential for normal hair growth, but true biotin deficiency is rare. In deficient people, supplementing with biotin can improve hair loss. However, in people with normal biotin levels, high-quality studies have not consistently shown that biotin supplements increase hair growth, thickness, or reduce shedding." (Read more about the complexities of biotin for hair growth.)

Before you abandon the thought of using biotin, though, you should know that it has another, perhaps less popular benefit: growing and strengthening brittle nails. That's according to two top dermatologists who say it might be your fix for short, bendy, breaking nails. Keep scrolling to learn everything you need to know.

What Is Biotin?

Biotin, or vitamin B7, is a water-soluble vitamin that's produced naturally in the body and found in many foods, including meat, eggs, salmon, sweet potatoes, lentils, and nuts. It plays an important role in converting food to energy and helps enzymes break down carboyhydrates, fats, and proteins. It's also important in cell signaling.

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Biotin & Nail Health

According to dermatologist Dara Spearman, MD, FAAD, biotin can really make a difference in the state of the nails, especially if they're damaged from one too many gel manicures. "Biotin can benefit the nails by boosting the production of keratin, which is the main protein that can be found in finger and toenails," she says. "Biotin can not only help with the growth, but also the healthiness of your nails."

Shah agrees, although she says proof in the form of scientific studies is still scarce. "The evidence for nails is better than for hair, although it's still limited. Several small studies suggest that biotin may improve brittle nails by increasing nail thickness. Biotin may help by supporting keratin, the primary structural protein that makes up nails. Additionally, biotin functions as a cofactor for enzymes involved in producing fatty acids and other molecules needed by rapidly growing tissues like nails. The exact mechanism isn't fully understood, but improved keratin organization and nail plate integrity are the leading theories."

Yep, the experts agree that biotin really can improve the strength and health of the nails. However, Shah says, "It's important to note that biotin doesn't necessarily make nails grow faster. Instead, stronger nails break less, so they can reach longer lengths."

How Often to Take Biotin for Nail Health

"The dose most often used in studies is 2.5 mg (2,500 mcg) daily, which is substantially higher than the recommended daily intake for adults (30 mcg/day), but it's the dose evaluated in most nail studies," Shah says. "Higher doses (such as 5,000–10,000 mcg) are commonly sold but haven't shown additional nail benefits."

Spearman agrees, saying the recommended dose is 2.5 mg, and that's what she suggests to anyone who's wanting to take it for nail-health purposes. "This is a healthy amount to rebuild the strength of finger and toe nails," she says.

As for how often to take biotin, both experts say once a day is enough. "
Because fingernails grow slowly, results take time to appear," Shah says. "Most studies found improvements after 2–3 months for early changes and 3–6 months for more noticeable improvement. If there has been no benefit after about six months, it's reasonable to reconsider whether it's helping."

Downsides & Drawbacks

The experts say biotin is generally considered safe, because it's water-soluble and serious side effects are uncommon. "However, there are some important drawbacks," Shah says. "The biggest concern is laboratory test interference. High-dose biotin can interfere with many blood tests, including tests for thyroid disease, myocardial infarction, certain hormone tests, some vitamin and other laboratory assays. This can lead to falsely high or falsely low results depending on the test, which has occasionally contributed to missed or delayed diagnoses."

That's why it's critical to tell your healthcare providers you're taking biotin supplements before having any blood work done. "Many clinicians recommend stopping biotin for at least 48–72 hours before laboratory testing, though some specialized tests may require a longer washout period depending on the dose and the assay," Shah says. "Other reported potential adverse effects include mild stomach upset or acne-like breakouts. Women who are pregnant or breastfeeding should discuss high-dose supplements with their clinician, even though biotin requirements are slightly higher during pregnancy."

Spearman adds that excessive biotin intake can cause side effects such as skin discomfort, trouble with sleep, nausea, and, interestingly, excessive doses can contribute to hair loss." The best way to avoid these side effects is by sticking to the recommended daily dosage.

5 More Ways to Strengthen Nails

The experts say biotin isn't the only way to strengthen the nails and keep them healthy. You should also:

• Moisturize your nails (hand creams and cuticle oils can help)
• Use a nail strengthener as needed
• Avoid harsh chemicals and salon processes
• Avoid repeated wet-dry cycling ("Wet-dry cycles weaken nails," Shah says. "Wearing gloves for dishwashing or cleaning can help.")
• Eat protein ("Since nails are made primarily of keratin, inadequate protein intake can contribute to weak nails," Shah says.)

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