Does Biotin Help Hair Growth? What the Evidence Actually Shows

Noticing more hair in your brush or seeing your parting become wider can be worrying. And when biotin appears in so many supplements, shampoos and hair treatments, it can feel like an obvious place to start.

Biotin does matter for normal hair health. If you are deficient, replacing it may help. But most people already get enough, and taking more has not been shown to reliably make hair grow faster or thicker.

So, is biotin worth trying? That depends on why your hair is changing. Here is what the evidence can tell you.

Does Biotin Help Hair Growth?

Biotin is an important factor for hair health and can help with hair growth when a deficiency is contributing to hair loss. Thinning hair is a recognised symptom of severe biotin deficiency, and replacing the missing vitamin can help correct deficiency related symptoms.

However, true biotin deficiencies are rare and for people who are not deficient, the evidence for hair growth is much less encouraging.

A 2017 review identified 18 published cases in which biotin was used for hair or nail changes. Everyone who improved had an underlying condition affecting their biotin status, hair or nails. The review found insufficient evidence to recommend biotin for hair growth in otherwise healthy people.*

A 2024 review found only 3 suitable clinical studies. The strongest included 46 women with diffuse hair loss. After 4 weeks, there was no significant difference in hair growth between those taking 10mg of biotin and those taking a placebo.⁺

A newer systematic review reached a similar conclusion. Across studies, biotin taken on its own did not produce consistent improvements in objective hair growth measurements. When combination treatments produced positive results, researchers could not determine whether biotin was responsible.^

*Patel DP, et al. (2017). A review of the use of biotin for hair loss.

⁺Yelich A, et al. (2024). Biotin for hair loss: teasing out the evidence.

^Moltó Balado P, et al. (2026). Effectiveness of biotin supplementation for hair growth in patients with alopecia: a systematic review.

When might biotin help?

Biotin may help if you have a confirmed deficiency or a medical condition that affects how your body absorbs or processes it. In this situation, supplementation replaces something your body is missing.

Can biotin prevent hair loss?

Biotin may prevent or improve hair changes caused by a deficiency. It does not provide general protection against hair loss.

If your thinning is caused by genetics, hormones, stress, illness, rapid weight loss, an iron deficiency or a thyroid condition, biotin will not address the underlying cause. Female pattern hair loss is influenced by genetic and hormonal factors and is not usually caused by a lack of biotin.*

*British Association of Dermatologists. (2024). Hair loss female pattern.

What Is Biotin and Why Can a Deficiency Affect Your Hair?

Biotin, also known as vitamin B7, is an essential vitamin. Your body uses it to help process fats, carbohydrates and amino acids from food.

Biotin helps maintain normal hair. However, maintaining normal hair is not the same as stimulating new growth or treating hair loss.

When someone has a severe deficiency, the processes that rely on biotin cannot work normally. This can affect several parts of the body and may lead to thinning hair, brittle nails and skin changes. The precise relationship between biotin and the hair cycle is not fully understood, so it is too simplistic to say that biotin directly produces keratin or activates hair follicles.

How do you know if you are deficient?

True biotin deficiency is rare, and hair loss on its own does not mean you have it.

When deficiency occurs, thinning hair may appear alongside brittle nails, a red or scaly rash around the eyes, nose or mouth, tiredness, tingling sensations or neurological symptoms.

People with certain rare genetic conditions can have difficulty processing biotin. Chronic alcohol exposure can affect absorption, while pregnancy and breastfeeding can change markers of biotin status. Conditions or surgery affecting nutrient absorption may also increase the risk of several deficiencies.

Should you test your biotin levels?

Routine biotin testing is not usually the first step when investigating hair loss. Serum biotin results are not considered a reliable way to identify a mild deficiency. A clinician will usually consider the pattern and timing of your hair loss, your diet, recent illnesses, stress, medicines, periods and family history. Depending on your symptoms, they may recommend tests for more common causes, such as iron deficiency, anaemia or thyroid problems.

*National Institutes of Health Office of Dietary Supplements. (n.d.). Biotin: fact sheet for health professionals.

How Much Biotin Should You Take for Hair Growth?

There is no clinically proven biotin dose for improving hair growth in people who are not deficient.

The NHS says most people should get all the biotin they need from a varied and balanced diet. It also says that taking 0.9mg or less a day from supplements is unlikely to cause harm.* This is safety advice, not a recommended hair growth dose or a maximum safe amount.

Many hair supplements contain considerably more biotin. A larger number on the label does not mean the product will deliver faster or better results.

If a clinician believes you are deficient, they can recommend an appropriate dose based on your health and the likely cause.

*NHS. (n.d.). B vitamins and folic acid.

How long does biotin take to work?

There is no reliable biotin hair growth timeline for people who are not deficient.\ Published reports* involving people with an underlying deficiency describe improvement over several months, but the causes, doses and results varied. These reports cannot tell us how quickly biotin will work for the average woman with thinning hair. Hair grows slowly, so be cautious of products promising dramatically thicker or longer hair within a few weeks.

*Yelich A, et al. (2024). Biotin for hair loss: teasing out the evidence.

Which Type of Biotin Is Best for Hair Growth?

Biotin is available in tablets, capsules, gummies, shampoos and serums. No particular formula has been shown to make biotin more effective for hair growth.

Tablets, capsules and gummies deliver biotin orally. They may help correct a deficiency, but the format itself is unlikely to change the result.

There is little clinical evidence that biotin applied to the scalp stimulates regrowth on its own.* If a serum contains both biotin and minoxidil, the ingredients should not be treated as though they have the same level of evidence. Minoxidil is the ingredient used to treat hair loss and promote regrowth.

*Moltó Balado P, et al. (2026). Effectiveness of biotin supplementation for hair growth in patients with alopecia: a systematic review.

Biotin During Menopause and After Pregnancy

Does biotin help menopausal hair thinning?

There is no good evidence that biotin specifically treats hair thinning during perimenopause or menopause unless you are also deficient.

Female pattern hair loss is influenced by genetic and hormonal factors and often becomes more noticeable with age. Biotin can support normal hair maintenance, but taking more of it will not correct the hormonal or genetic processes affecting the follicles.*

*British Association of Dermatologists. (2024). Hair loss female pattern.

Does biotin help postpartum hair loss?

Noticeable shedding a few months after having a baby is common. It is usually caused by falling oestrogen levels moving more hairs into the shedding phase, rather than by a biotin deficiency. This shedding is usually temporary, and most women regain their normal fullness by their child’s first birthday. Biotin is unlikely to stop normal postpartum shedding unless you are also deficient.* Speak to your GP, midwife or pharmacist before taking a high dose supplement while pregnant or breastfeeding. If your hair has not begun recovering after a year, or the loss is severe or patchy, speak to a clinician.

*American Academy of Dermatology. (2025). Hair loss in new mums: dermatologist tips.

Can You Get Enough Biotin From Food?

Most people can get enough biotin from their usual diet. Foods containing it include cooked eggs, fish, meat, nuts, seeds, sweet potatoes and some vegetables.

Raw egg whites contain a protein called avidin, which binds to biotin and can reduce its absorption.* Eating foods containing raw egg occasionally is unlikely to cause a problem, but regularly consuming large quantities of raw egg whites may affect your biotin levels.

You do not need to build every meal around biotin. Eating a varied and balanced diet should usually provide the small amount your body needs.

Before taking a supplement, check whether biotin is already included in your multivitamin, hair supplement or treatment. Using several products may give you a much higher total amount without providing any additional benefit.

*National Institutes of Health Office of Dietary Supplements. (n.d.). Biotin: fact sheet for health professionals.

Can You Take Too Much Biotin?

Biotin is water soluble, so your body removes what it does not need through your urine. No upper intake limit has been established because research has not identified a clear level at which biotin itself becomes toxic.

However, this does not mean that any amount is risk free or that taking more will provide greater benefits for your hair.

The NHS says that taking 0.9mg or less a day from supplements is unlikely to cause harm. This is not a maximum safe dose. It reflects the limited evidence available about regularly taking larger amounts.

Does Biotin Cause Side Effects?

Biotin is generally well tolerated, and clear physical side effects have not been consistently linked to it. Supplements may contain other vitamins, flavourings or ingredients that can cause symptoms. If you feel unwell or develop a rash after starting one, stop taking it and speak to a pharmacist or clinician.

Can biotin affect blood test results?

The main known risk from higher dose biotin is its effect on certain blood tests. It can produce results that appear falsely high or low, potentially affecting tests used to assess thyroid function, hormones and troponin, which is measured when a heart attack is suspected.*

Tell your clinician and the person taking your blood that you use biotin. If you have a test coming up, follow their advice about whether and when to pause it. Do not stop a prescribed treatment without speaking to your clinician.

*National Institutes of Health Office of Dietary Supplements. (n.d.). Biotin: fact sheet for health professionals.

Why Do Some Hair Loss Treatments Contain Biotin?

The role of each ingredient in hair loss treatments should be clear. Biotin contributes to the maintenance of healthy hair. Alone, it only contributes to hair growth if you have a biotin deficiency.

Supplements such as biotin acts as a good foundation for hair health and is often used in combination with clinically proven ingredients such as Minoxidil is used to treat hair loss and promote regrowth. Spironolactone may be prescribed to reduce the hormonal effects that contribute to female pattern hair loss.

Oral minoxidil and spironolactone are prescribed off label for female pattern hair loss in the UK. This means they are licensed medicines being prescribed for a use that is not included in their marketing authorisation. A clinician can prescribe them this way when they consider it clinically appropriate.

Combining vitamins and medicated ingredients provides a practical benefit by placing hair loss treatment and nutritional support within one routine.

Does Biotin Help Hair Growth? The Bottom Line

Biotin is an essential nutrient that supports overall health and the maintenance of healthy skin, hair, and nails, but taking extra biotin alone is not a shortcut to faster hair growth.

If you are deficient, replacing it may help the hair changes caused by that deficiency. If you already get enough, there is little evidence that a supplement will make your hair grow faster, thicker or fuller.

If your hair continues to thin, finding out what may be causing it is more helpful than trying increasingly strong supplements. Once you understand the likely cause, you can consider treatment that addresses it.