Note: The U.S. Food and Drug Administration (FDA) does not approve supplements for safety or effectiveness. Talk to a healthcare professional about whether a supplement is the right fit for your individual health, and about any potential drug interactions or safety concerns.

Biotin, also known as vitamin B7, is an essential nutrient found in many foods, including meat, fish, eggs, nuts and seeds, and sweet potatoes. It helps turn the protein, carbohydrates, and fats from the foods you eat into energy.

Vitamin B7 also helps make proteins that form hair, making it a common addition to hair supplement formulas that claim to battle hair loss and boost hair thickness.

You can find supplements that contain biotin only or as part of a B complex, multivitamin, or hair health formulation. It’s even added to some topical hair products like shampoo. But do biotin supplements help with hair growth and loss?

Hair goes through natural growth and shedding cycles, so you’re continually losing — and growing — hair every day. How well your hair grows depends on the health of the hair follicles (the pores from which a hair grows). The health of the hair follicles is affected by various factors, including hormonal changes and stress.Biotin’s perks for hair health are twofold. One, hair follicles need a lot of energy to perform their functions, and biotin produces energy at the hair root to support hair growth.Biotin also helps break down amino acids (the building blocks of protein) from food. These amino acids can then be used to create the proteins keratin and collagen, which make up skin and hair, says Lauren N. Taglia, MD, PhD, a dermatologist with Northwestern Medicine Regional Medical Group in Naperville, Illinois.

Most of us get the biotin we need from food. “Biotin deficiency is rare in industrialized countries. This is likely due to the fact that there are a number of common food sources rich in biotin,” says Dr. Taglia.

Your gut microbiome (the bacteria and other microbes that live in the gastrointestinal tract) also produces biotin, she adds.

Still, some people are at risk for not getting enough vitamin B7, including those with alcohol use disorder, biotinidase deficiency (a rare genetic disorder that affects how the body processes biotin), and people who are pregnant or breastfeeding. People with malnutrition, those who take certain antibiotics or seizure medications, and those who smoke are also at risk for a biotin deficiency.Since hair loss is a sign of biotin deficiency, biotin supplements are often marketed as promoting hair growth and strength. But these claims don’t have much evidence to back them up.

Biotin is found in many hair growth supplements and may help with hair growth and thickness in those with a biotin deficiency, says Elizabeth Bahar Houshmand, MD, a board-certified dermatologist based in Dallas.

Research suggests that biotin supplements may be helpful for pediatric hair conditions such as uncombable hair syndrome (a rare genetic disorder that causes hair to be dry, frizzy, and difficult to flatten). And some case studies show that biotin supplements may improve hair regrowth in people with a genetic biotin deficiency that causes alopecia (hair loss). But Taglia points out that the evidence comes from low-quality studies.

Biotin supplements may not be helpful for people who get enough biotin through diet. “To date, we do not have evidence-based studies supporting the use of biotin supplements in those without biotin deficiency,” says Dr. Houshmand. Indeed, several manufacturers have removed biotin from newer hair supplement formulations, she adds.

The authors of a review of three studies note that supplement marketing claims have created the public perception that taking biotin supplements can improve hair health.

Given that there’s not yet evidence to support the use of biotin supplements to promote hair growth, Houshmand says she wouldn’t necessarily suggest patients try it. Instead, she considers a patient’s intake of other nutrients that promote hair health, such as protein, zinc, selenium, iron, and vitamin D. Depending on the nutrient, this can be done by reviewing a person’s diet or looking for deficiency through a blood test. Biotin supplements alone will not reduce hair loss or promote hair growth and thickness.

But if you’re deficient in biotin, your provider may recommend dietary changes and supplements to bring your biotin levels within a healthy range. A deficiency is considered rare among those eating a balanced diet, but it can occur with chronic alcohol exposure, pregnancy, or breastfeeding.Adequate intake (AI, the amount that’s considered sufficient to meet the nutritional needs of most healthy people of a specific age or gender) of biotin is 30 micrograms (mcg) for adults and 35 mcg for people who are breastfeeding. Appropriate biotin dosages vary depending on the severity of the deficiency. If you have a biotin deficiency, discuss the amount you need with your healthcare provider.There’s no evidence that taking biotin at high intakes is harmful. Biotin is a water-soluble vitamin, meaning your body gets rid of any excess in urine. Still, you should not take excessive levels for any reason, including to improve hair growth.While side effects are rare, too much biotin can cause:

• Allergic reactions (typically, skin rashes)

• Nausea

• Cramping and abdominal pain

In addition to side effects, biotin supplements carry potential risks.

One risk of biotin beyond the recommended 30 mcg daily is it can skew the results of certain laboratory tests, such as those used to assess thyroid function. Before a blood test, sure to tell your healthcare provider and the lab if you’re taking a biotin supplement. They may advise you to stop 7 to 10 days before testing, says Houshmand.Another potential risk of taking biotin supplements is the U.S. Food and Drug Administration (FDA) does not approve dietary supplements for safety or efficacy before they’re sold. Instead, it’s up to the manufacturer to ensure their product is labeled correctly and free of contaminants that could pose a health risk.If you’re still interested in taking a biotin supplement, look for one with an independent third-party certification from organizations like NSF, ConsumerLab, and U.S. Pharmacopeia (USP). A third-party certification validates that the supplement contains what it says it does and does not contain hidden substances.

• Biotin may promote hair health by creating energy and protein for hair follicles to grow.

• There is a lack of evidence that this B vitamin is effective for hair growth in people who do not have a biotin deficiency.

• While biotin supplements may promote hair health in people with a deficiency, the evidence is weak.

• Biotin is not toxic, but it may interfere with bloodwork results and cause side effects like nausea and cramping, so discuss biotin supplements with your healthcare provider before you take them.