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Is biotin really the secret to great skin, hair and nails?
We investigate whether the so-called 'beauty vitamin' actually makes a difference, or if you’re just flushing money down the drain
Biotin is a staple inclusion in many 'beauty' supplements, especially those that claim to help boost your skin, hair and nails.
But does it actually work, and do you really need a dose that's 10,000% of the daily reference value (NRV)? We've delved into the evidence and asked the experts to find out.
Read on to discover what it actually can do, how much you need and what to watch out for.
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What is biotin?
Biotin is another name for vitamin B7. It’s a water-soluble vitamin that is one of the eight B vitamins.
B7’s role is to help convert food into energy, and it is also essential for the production of keratin, the protein that makes up your skin, hair and nails.
It's because of this connection that it's frequently found in everything from gummy supplements that promise to 'glow up' your hair and skin to fortified juices and even high-end shampoos.
Marketing claims for these sorts of supplements often claim biotin will restore and boost your hair growth, strengthen your nails and give your skin a healthy glow.
Our biotin experts
As part of our research into biotin supplements, we looked into the available clinical research and evidence, checked what health claims are approved for biotin and asked two consultant dermatologists with expertise in hair and nail issues for their expert input.
Our experts are:
- Dr Leila Asfour - Consultant dermatologist and president of the British Hair and Nail Society
- Dr Sharon Wong - Consultant dermatologist, president of the Institute of Trichologists and founder of DOSE
So, do biotin beauty claims stack up?
Not really. Biotin is essential for healthy hair and nails, but unless you have a genuine deficiency, which is rare, taking extra supplements is unlikely to have much impact.
Consultant dermatologist and hair/scalp expert Dr Sharon Wong says: 'Both clinical studies and real-world experience with patients demonstrate that supplementing in the absence of a deficiency confers no benefit in improving hair growth.'
So why is it touted as a beauty supplement? There are seven authorised claims that supplement brands can make about biotin, as listed on the Great Britain Nutrition and Health Claims Register, including that it contributes to the 'maintenance of normal hair and skin'.
However, the key word here is maintenance. If you already have a healthy, normal baseline, biotin simply keeps it there. In other words, while it will maintain your already healthy hair, it will not thicken it or repair damage. There is a big difference between the legal definition of maintenance. and marketing claims of a Rapunzel-like transformation.
Biotin: evidence vs claims
When we looked closer, we didn't find much convincing evidence that biotin would have results beyond the standard maintenance of healthy hair and skin. And it's worth noting there are no approved claims for nails.
Hair: There is no strong evidence that biotin increases hair growth or shine. Studies showing improvement almost exclusively involve patients with pre-existing medical conditions. If your hair is thinning due to genetics, stress or male-pattern baldness, biotin is unlikely to help.
Nails: Three small but often-cited studies from the late 80s and early 90s suggested that high doses of biotin might increase thickness in people with brittle nail syndrome. However, these studies were tiny (all looked at fewer than 50 people) and two of the three lacked a placebo control group.
Skin: The evidence here is the weakest of all. While a severe biotin deficiency can cause a red, scaly rash, there is zero clinical evidence that extra biotin clears acne, reduces wrinkles or improves skin texture in healthy individuals.
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How common is biotin deficiency?
True biotin deficiency is very rare. This is partly because biotin is found in many everyday foods, from bread to nuts, and partly because your large intestine is actually a sort of biotin factory. Friendly bacteria synthesise biotin from scratch in your gut, as they ferment the fibre you eat.
Your body also does an excellent and efficient job of recycling the biotin it already has, freeing it up to be used again. So even if your diet temporarily lacks biotin, your body can use what it already has.
The NHS advises that you should easily be able to get enough biotin from your diet. So, unless you are pregnant, have a specific genetic disorder or consume huge amounts of raw egg whites (the protein avidin in raw whites blocks biotin absorption), you likely already have all you need.
If you aren't deficient, your body simply flushes the excess out, meaning the money you spend on high-strength supplements is essentially flushed down the toilet.
Biotin supplements and blood tests: what you need to know
There's a relatively little-known side effect of taking biotin supplements that's worth being aware of: it can interfere with blood test results, potentially impacting your wider health.
The Medicines and Healthcare regulation authority (MHRA) warns that biotin can significantly interfere with lab tests at doses as low as 150mcg. Many high-street supplements contain 5000-10,000mcg, massively exceeding this threshold.
We asked consultant dermatologist Dr Leila Asfour for her advice, and she said: 'If you are not deficient, ie have a clinical need to take biotin, then we would not recommend taking it.
'The risks outweigh the benefits in someone who is not deficient. There is increasing medical literature demonstrating that biotin interferes with the interpretation of results of important blood tests including thyroid function, troponins (a protein in the heart muscle which helps us with diagnosis of heart attacks), some cancer markers are also affected giving false high or low results, which can have a major impact on treatment decisions.'
Because lab tests often use biotin as a binder, having high levels in your blood can cause:
False-negative heart attack tests: Biotin can hide Troponin, the marker used to diagnose a cardiac event.
Thyroid confusion: It can mimic Graves' Disease, leading to unnecessary prescriptions of strong medicines.
Biotin is also used as a marker in hormone tests, so it could skew results relating to pregnancy, fertility and endocrine disorders.
If you are taking biotin or a supplement that contains it, tell your doctor in advance if they recommend you have any blood tests.
The verdict on biotin
For most healthy adults, biotin supplements are a waste of money.
Dr Sharon Wong confirms: 'Taking supplements without understanding the contributory factor(s) can delay the diagnosis and therefore starting targeted treatment to address the root cause. It is a scenario I encounter very frequently – months to years of endless trying of products and supplements with no results. Furthermore, over-supplementing with biotin can lead to skewed lab tests, including thyroid and heart health markers.'
What to do instead:
For hair: Save your money, assess the basics such as sleep, stress levels and diet, which can all have an impact, and potentially check your iron levels. Iron deficiency can cause hair loss or thinning and is a relatively common nutrient deficiency, particularly if you have heavy or frequent periods, or are vegan or vegetarian.
For skin: Again, save your money. A balanced diet and a good SPF are far more effective.
For nails: There is weak evidence that biotin supplementation might help with chronic brittleness, but you would need to be prepared to wait six months for results that may never come.
If you do still want to try biotin, don't buy the expensive 10,000mcg ‘mega-doses’. A standard multivitamin (50mcg–100mcg) is more than enough. And most importantly: stop taking it 72 hours before any blood test and always tell your doctor you are using it.
