The short version
• Biotin is vitamin B7, one of the B vitamins (NHS).
• Biotin contributes to normal energy-yielding metabolism and to normal macronutrient metabolism, meaning how your body uses carbohydrate, fat and protein (GB NHC Register).
• Biotin contributes to the maintenance of normal hair and normal skin (GB NHC Register).
• It also contributes to the normal functioning of the nervous system and to normal psychological function (GB NHC Register).
• Most people can get all the biotin they need from a varied and balanced diet (NHS).
• Taking 0.9 mg or less of biotin a day in supplements is unlikely to cause any harm (NHS).
• Many hair, skin and nail products contain far more biotin than this, and high-dose biotin can interfere with some laboratory tests (FDA).
• If you take biotin and are having a blood test, tell your doctor and the person taking your sample (FDA).
• The authorised claim is about maintaining normal hair. There is no authorised claim that biotin makes hair grow faster or thicker.
Walk along any pharmacy aisle and you will see biotin on the front of hair, skin and nail products, often in large print and large numbers. For many people, it is the only B vitamin they could name.
Yet biotin's day job has little to do with appearance. It is one of the B vitamins that help your body release energy from food, and the NHS notes that most people get all the biotin they need from a varied and balanced diet (NHS). There is also a safety point that rarely makes it onto the packaging: high-dose biotin can interfere with some laboratory tests, a risk recognised both by the US Food and Drug Administration (FDA) and within the NHS (Manchester University NHS Foundation Trust).
So, this piece explains what biotin is, what it does according to the authorised science, how much you need, the truth about biotin and hair, and how to read a biotin label so you know exactly what you are taking.
What is biotin?
Biotin is one of the B vitamins, and is also known as vitamin B7 (NHS). Like the other B vitamins, it is water-soluble, which means the body does not store large amounts and needs a regular supply from food.
You may also see it called vitamin H on older or non-UK labels. It is the same nutrient.
What does biotin do in the body?
Biotin has a broad set of authorised health claims on the GB Nutrition and Health Claims Register. Biotin contributes to:
• normal energy-yielding metabolism
• normal macronutrient metabolism
• normal functioning of the nervous system
• normal psychological function
• the maintenance of normal hair
• the maintenance of normal skin
• the maintenance of normal mucous membranes
Biotin acts as a cofactor, a helper molecule, for five important enzymes known as carboxylases. These enzymes are involved in processes including fatty acid synthesis, glucose production and the metabolism of certain amino acids (NIH Office of Dietary Supplements).
This helps explain why biotin has authorised roles in normal energy-yielding and macronutrient metabolism. Rather than providing energy itself, biotin supports the biochemical processes through which the body uses nutrients from food.
For readers interested in the underlying science, two of the best-known biotin-dependent enzymes are acetyl-CoA carboxylase, which is involved in fatty acid synthesis, and pyruvate carboxylase, which takes part in glucose metabolism (NIH Office of Dietary Supplements).
Biotin and hair: what the claim really says
Biotin is heavily associated with hair, and it does have an authorised claim: biotin contributes to the maintenance of normal hair (GB NHC Register).
Read that wording carefully. It is about maintaining normal hair, not making hair grow faster, thicker or longer. There is no authorised claim for these additional effects.
In its scientific assessment, the European Food Safety Authority (EFSA) recognised biotin's role in maintaining normal hair, but also noted that the amounts needed to support its authorised health claims can be readily obtained through a balanced diet (EFSA, 2010).
This is an important distinction. An authorised health claim confirms a recognised nutritional function; it does not mean that taking additional biotin will necessarily change hair growth or thickness in someone who already gets enough.
This is exactly the kind of detail we think you deserve to know before you spend money.
How much biotin do you need?
The NHS advises that you should be able to get all the biotin you need from a varied and balanced diet, as biotin is found in a wide range of foods (NHS).
On UK supplement labels, biotin is compared with a Nutrient Reference Value (NRV) of 50 micrograms (µg) (Regulation 1169/2011, Annex XIII). For supplements, the Department of Health and Social Care advises that taking 0.9 mg (900 µg) or less a day is unlikely to cause any harm (NHS).
Why biotin can affect blood test results
Many laboratory tests use biotin as part of their chemistry. When a person has high levels of biotin in their blood from supplements, it can interfere with some of these tests and cause incorrect results that may go undetected (FDA).
The US FDA has been particularly concerned about falsely low results on some tests for troponin, a marker used to help diagnose heart attacks (FDA).
Within the NHS, Manchester University NHS Foundation Trust also warns that high-dose biotin can affect the accuracy of certain laboratory tests, and notes that the risk depends on the dose and the testing method used (Manchester University NHS Foundation Trust).
The practical advice is simple: if you take a supplement containing biotin, including a multivitamin or a hair, skin and nails product, tell your doctor and the person taking your blood sample (FDA).
How to read a biotin label
Biotin labels are a good example of why the units matter.
• Micrograms or milligrams? Biotin is usually listed in micrograms (µg or mcg). 1 mg is 1,000 µg.
• % NRV. A product providing 50 µg delivers 100% NRV. A product providing 10,000 µg (10 mg) delivers 20,000% NRV, more than ten times the 0.9 mg the NHS describes as unlikely to cause harm (NHS).
• Hidden sources. Biotin appears in many multivitamins, B-complex products and beauty supplements. Add them up if you take more than one.
• The wording. Responsible products use the authorised claim language, such as "contributes to the maintenance of normal hair", rather than promises of growth.
Common questions
What is biotin?
Biotin is vitamin B7, one of the B vitamins (NHS). It contributes to normal energy-yielding metabolism and to the maintenance of normal hair and skin (GB NHC Register).
What does biotin do for the body?
Biotin contributes to normal energy-yielding metabolism, normal macronutrient metabolism, the normal functioning of the nervous system, normal psychological function, and the maintenance of normal hair, skin and mucous membranes (GB NHC Register).
Does biotin make your hair grow?
Biotin contributes to the maintenance of normal hair (GB NHC Register). There is no authorised claim that it makes hair grow faster or thicker, and EFSA noted that the amounts needed for its authorised roles can be readily obtained through a balanced diet (EFSA, 2010).
How much biotin is safe to take?
The Department of Health and Social Care advises that 0.9 mg or less a day of biotin from supplements is unlikely to cause any harm (NHS).
Can biotin affect blood tests?
Yes. High levels of biotin can interfere with some laboratory tests, including some troponin tests (FDA), and the risk depends on the dose and the test used (Manchester University NHS Foundation Trust). Tell your doctor if you take biotin before a blood test.
The bottom line
Biotin is a hard-working B vitamin with a wide set of authorised roles, from releasing energy from food to maintaining normal hair and skin. Most people get enough from a balanced diet, and for those who supplement, the NHS guidance of 0.9 mg or less a day is a sensible ceiling.
Be wary of products that lead with enormous numbers and implied promises of growth, and remember to mention biotin before any blood test. If you do choose a supplement, our Biotin gives you a clearly stated amount and uses only authorised claim wording.
Food supplements should not be used as a substitute for a varied, balanced diet and healthy lifestyle. If you are pregnant or breastfeeding, taking medication or have a medical condition, consult your healthcare practitioner before use.
