Why biotin isn't a miracle hair-growth supplement - and the side effects you should know before taking it

• Biotin does help with hair growth as long as you have a biotin deficiency.
• Signs of a biotin deficiency include fatigue, loss of hair, and brittle nails.
• Chat with your doctor about the right dosage, which is typically around 5 mg per day.

Biotin is a popular vitamin supplement often marketed for its ability to grow healthy hair, skin, and nails. However, there is limited research on the relationship between biotin and hair. And, of the limited studies, most indicate biotin only thickens and lengthens hair if you have a biotin deficiency.

Here is what you need to know about biotin, its relationship to healthy hair, and possible side effects.

What is biotin?

Biotin, aka B7 or vitamin H, is an essential vitamin B nutrient that can be found naturally in some foods or taken as a dietary supplement. Biotin is important for several reasons, including:

• Converts nutrients, such as carbohydrates, protein, and fats, into energy.
• Aids in the production of keratin, which helps keep your skin, hair, and nails healthy.

Here are some dietary sources of biotin:

You can also take biotin as an over-the-counter supplement. Your recommended daily intake varies depending on your age and gender, but for an adult male or female it is 30 mcg.

It's important to consult your doctor before taking a biotin supplement to determine what dosage is best for you.

Biotin for Hair Growth

Biotin helps in the production of keratin, a protein that makes up your hair, skin, and nails. Because of this, many companies tout biotin for its ability to help with hair growth, but there is very little research on the relationship between the two.

"What we usually do in clinical practice is recommend biotin for people with dry, breaking hair, or brittle nails," says Olga Bunimovich, MD, a dermatologist at the University of Pittsburgh Medical Center.

What the research says: Only one 2012 study found that women with thinning hair significantly benefited from taking a supplement containing biotin compared to women taking a placebo. Another 2017 review of biotin for hair loss found that the vitamin may benefit those with a biotin deficiency, but there was little evidence to support whether taking biotin aided in hair growth in healthy individuals.

People may be deficient for various reasons, such as:

• Pregnancy
• Alcoholism
• Biotinidase deficiency (BTD), a rare genetic disorder that prevents your body from recycling its biotin. It is incredibly uncommon in the United States with only 1 in 75,000 babies born with BTD.

Symptoms of a biotin deficiency progress gradually over time and can include:

• Thinning hair or loss of hair
• Brittle nails
• A rash around your eyes and mouth
• Lethargy or depression

General advice: When biotin is prescribed, the typical dosage is around 5 mg a day and it can take a minimum of three to six months for hair thickening and growth, says Bunimovich. This is about 166% of your daily needs.

If you are experiencing hair loss or hair shedding, it may be due to another nutritional issue, like an iron deficiency, or an underlying health condition, such as a thyroid disorder. Taking biotin would not be effective for either of these conditions.

Biotin side effects

Biotin is a water-soluble vitamin, meaning any excess is flushed out through your urine and not stored in your body.

Therefore, you cannot overdose on biotin, but some people may experience an upset stomach or diarrhea when taking biotin supplements. Additionally, biotin is not harmful to your kidneys if taken within the appropriate dosage amounts.

Studies found no adverse effects in 10 to 50 mg/day to as much as 200 mg/day. But, it's important to keep dosage below 5 mg a day, says Elizabeth Damstetter, MD, a dermatologist and assistant professor at Rush Medical Center. That's because biotin absorbed in your bloodstream may interfere with test results for hours or days after the fact, such as thyroid hormone tests or a troponin test, which helps diagnose heart attacks.

It's important to let your doctor know you are on biotin in these cases.

Biotin can also have an interaction with other medications, such as anticonvulsants, which can decrease the levels of biotin in your body. Long-term antibiotic use may also negatively impact the biotin levels in your gut.

If you are on any of these medications, speak with your healthcare provider before taking biotin.

Insider's Takeaway

Biotin is a water-soluble vitamin that helps produce the protein keratin, which is essential for healthy hair, nails, and skin. While there is limited research on the effect biotin has on hair growth, people with a biotin deficiency may see healthier hair if they start supplementing.

There are minimal side effects to biotin, but taking more than 5 mg could interfere with certain medical tests or interact with some medications. If considering biotin for your hair, consult your doctor to determine if it's right for you.

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