Biotin
Biotin (vitamin B7, sometimes called vitamin H) is a water-soluble B-vitamin the body uses as an enzyme co-factor for fat, sugar, and protein metabolism. The UK NRV is 50 µg/day. Most adults eating any varied diet meet that easily. High-dose biotin (5,000-10,000 µg) is widely sold for hair, skin, and nails — but it can falsify common blood tests including troponin and TSH.
Camden Medicals editorial · Last reviewed 12 June 2026 · Next review June 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Vitamin
- NHS daily RNI
- 50 µg
- Typical supplemental
- 7.5 µg per portion — the GB NHC threshold to carry the authorised hair / skin claim.
- Top use evidence
- Strong
On this page
What it is
Biotin is a small water-soluble B-vitamin (chemically a fused imidazolidinone-thiophane ring with a valeric-acid side chain) that the body uses as the prosthetic group for five carboxylase enzymes: pyruvate carboxylase, propionyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, acetyl-CoA carboxylase 1, and acetyl-CoA carboxylase 2. These enzymes carry single-carbon units in fatty-acid synthesis, glucose production from non-carbohydrate sources, and the breakdown of certain amino acids (including leucine).
Biotin is widely distributed in food. Egg yolk, liver, salmon, soybeans, sunflower seeds, sweet potato, almonds, and yeast are all good dietary sources, and gut bacteria contribute small amounts. Cooking generally preserves biotin; dietary inadequacy is uncommon in healthy adults eating any varied UK diet.
The supplemental form sold in the UK is D-biotin — the biologically active stereoisomer, identical to the form found in food. UK supplements range from 7.5 µg gummies (the regulatory minimum to carry the GB NHC claim) up to 10,000 µg (10 mg) tablets — a 1,000-fold spread above the NRV. Higher dose does not equal higher benefit, and at the megadose end it begins to cause problems for blood-test interpretation.
At a glance
- UK NRV (Nutrient Reference Value): 50 µg/day, met easily from a varied diet. The threshold for a GB-authorised health claim is 7.5 µg per portion (15% NRV).
- Authorised UK claims include biotin's contribution to the maintenance of normal hair and skin, to normal energy-yielding metabolism, and to normal psychological function (GB NHC Register; seven claims in total).
- High-dose biotin (5,000-10,000 µg) is sold widely for hair growth. There are no good randomised trials in healthy non-deficient adults showing it improves hair, skin, or nails (Patel/Swink/Castelo-Soccio 2017).
- Critical safety point: high-dose biotin interferes with many immunoassay-based blood tests — including cardiac troponin, TSH, hCG (pregnancy), parathyroid hormone, and vitamin D. NICE NG145 advises clinicians to ask about biotin before thyroid tests. Stop high-dose biotin at least 48-72 hours before any blood test, or as advised by your lab.
What people use it for
Adults eating a varied UK diet
The UK NRV is 50 µg/day and most people meet it easily from food. The NHS notes that biotin is found in a wide range of foods and that gut bacteria also produce it; routine supplementation is not generally needed. [1]
Some evidenceStrongPeople with hair-thinning or brittle-nail concerns
Two older uncontrolled case series (Floersheim 1989, n=45 evaluable; Hochman 1993, n=35) reported improvement in nail firmness after several months of 2.5 mg/day biotin. Neither was a randomised controlled trial. A 2017 review of biotin for hair loss (Patel/Swink/Castelo-Soccio, Skin Appendage Disord) concluded that evidence supporting routine biotin use in healthy people is limited and that supplementation is reasonable mainly when there is genuine biotin deficiency. Talk to a pharmacist or GP if hair or nails are changing — there are common medical causes (thyroid disease, iron deficiency, post-pregnancy telogen effluvium, certain medicines) that biotin will not address. [12,13,10]
Some evidenceLimitedPeople with diagnosed biotinidase deficiency or holocarboxylase synthetase deficiency
These are inherited metabolic disorders, typically diagnosed by neonatal screening or in childhood. Lifelong biotin replacement (typically 5-20 mg/day) under specialist care prevents seizures, developmental delay, alopecia, and skin rash. This is a clinical pathway, not a consumer-supplement use case — paediatric metabolic teams direct dosing. [6]
Some evidenceStrongPregnant or breastfeeding women
Biotin requirements may rise modestly in pregnancy and lactation, and marginal biotin status is more common than once thought. UK NHS guidance is to obtain biotin from a varied diet rather than routine high-dose supplements; pregnancy is not a context for self-medicating with megadose biotin. Speak to your midwife, GP, or pharmacist before starting any supplement. [6,1]
Some evidenceLimitedBodybuilders, biohackers, and people taking high-dose B-complex stacks
High-dose biotin (often 5,000-10,000 µg) appears in many hair-skin-nails and bodybuilding stacks. The most clinically important issue here is not whether it grows hair (the evidence is weak) but that megadose biotin can falsify common blood tests for several days after the last dose — including cardiac troponin (used to diagnose heart attack), TSH and free T4 (thyroid), hCG (pregnancy), parathyroid hormone, and 25(OH) vitamin D. Stop high-dose biotin at least 48-72 hours before any blood test, longer if your lab instructs. [9,14,11]
Some evidenceStrong
How it works
As a covalently-bound prosthetic group on five carboxylase enzymes, biotin transfers single carbon (CO2) units in fatty-acid synthesis, gluconeogenesis, and the catabolism of branched-chain amino acids.
Common myths
Myth"High-dose biotin makes hair grow"
RealityThere is no good randomised controlled trial in healthy non-deficient adults showing biotin improves hair growth or density. The 2017 review of biotin for hair loss (Patel, Swink, Castelo-Soccio) concluded the evidence base is limited and that biotin supplementation is reasonable only where biotin deficiency is documented. Hair-loss conditions with effective UK treatments (androgenetic alopecia, alopecia areata, telogen effluvium with treatable causes) need a diagnosis, not a megadose biotin. [10]
Myth"Biotin is safe at any dose because it is water-soluble"
RealityWater-soluble does not mean unlimited. While biotin itself does not have a recognised toxicity at megadose, doses of 5,000-10,000 µg interfere with many clinical immunoassays for days after the last dose. Affected tests include cardiac troponin, TSH, hCG, parathyroid hormone, and vitamin D. The FDA issued safety communications on this in November 2017 and again in November 2019 after a death from a missed heart-attack diagnosis. The interference is the safety story, not direct toxicity. [9,14]
Myth"Vegans need extra biotin"
RealityBiotin is widely distributed in plant foods (soybeans, sunflower seeds, sweet potato, oats, almonds, legumes, yeast). A varied vegan diet is not a recognised risk factor for biotin inadequacy in adults. Marketing biotin as a special vegan need is not evidence-based. [6]
Myth"Biotin is a remedy for alopecia"
RealityThere is no evidence that biotin reverses alopecia of any specified clinical type in adults with normal biotin status. The exception is the characteristic alopecia of inherited biotinidase or holocarboxylase synthetase deficiency, which responds to replacement biotin under specialist care; that is a rare paediatric-metabolic diagnosis, not a generalisable adult story. Speak to a GP if you are losing hair — diagnosis guides management. [10,6]
Common online questions
Synthesised from the questions UK shoppers most often ask online about Biotin. Each answer is editorial and links to its evidence in the Sources list below.
How much biotin do you take for hair, skin, and nails?
The marketing answer and the regulatory answer are very different. To carry a GB-authorised "biotin contributes to the maintenance of normal hair / skin" claim a product needs only 7.5 µg per recommended daily portion (15% of the 50 µg NRV). Most "high strength" biotin products in the UK declare 5,000-10,000 µg — a 100- to 200-fold step above what regulation requires the claim. There is no good randomised trial evidence that the higher dose does more in healthy non-deficient adults, and the higher dose is the dose that interferes with blood tests. If hair, skin, or nails are changing, talk to a pharmacist or GP first — there are several common medical causes (thyroid disease, iron deficiency, post-pregnancy telogen effluvium) that no biotin dose will address. [10,8]
How long does it take to see results?
There is no validated time-to-effect for biotin in healthy non-deficient adults because the underlying effect in this group is not well established. The two small uncontrolled nail-brittleness case series (Floersheim 1989, Hochman 1993) used 2.5 mg/day for an average of 5-6 months before photographing firmer nails. Hair grows from the scalp at roughly 1 cm a month, so any genuine effect on hair would take months to appear and would be confounded by the natural hair cycle and any concurrent change (diet, stress, iron status). Honest position: if you stop biotin and nothing changes, that is informative. [13,12]
Does biotin really interfere with blood tests?
Yes, and the safety angle is the most important thing on this page. Many UK NHS lab assays use the streptavidin-biotin binding system in their design; circulating biotin from a high-dose supplement saturates the binding and gives wrong results. Affected tests include cardiac troponin (used to diagnose heart attack), TSH and free T4 (thyroid), hCG (pregnancy), parathyroid hormone, vitamin D, and many tumour markers. The FDA issued public warnings in 2017 and 2019 after a patient died from a missed heart attack linked to this interference. Standard UK lab guidance is to stop high-dose biotin at least 48-72 hours before any blood test, and longer if your lab instructs. [9,14,11]
Can I take biotin while pregnant?
Pregnancy biotin status can be marginal but the clinical significance is uncertain and routine megadose supplementation is not recommended. UK NHS guidance is to obtain biotin from a varied diet. The UK NRV is unchanged in pregnancy. Pregnancy is not a context for self-medicating with high-dose supplements — speak to your midwife, GP, or pharmacist before starting any supplement. [1,6]
I heard raw egg whites cause biotin deficiency — is that true?
Mechanistically yes, practically very rarely. Avidin, a protein in raw egg white, binds biotin tightly and prevents its absorption. The classic "egg-white injury" deficiency was described in volunteers fed extreme amounts of raw egg white for weeks in 1940s metabolic experiments. Cooking denatures avidin completely. Eating cooked eggs has no meaningful effect on biotin status. The only modern caution is for people who consume large amounts of raw egg white in protein-shake powders day after day. [6]
Biotin gummy or tablet — does it matter?
The form on UK shelves is D-biotin in both formats. Biotin is small and chemically stable; absorption is not a strong differentiator between gummy and tablet at the doses consumers typically take. The choice usually comes down to preference (chewable vs swallow), cost per microgram, and whether the gummy carries added sugar. A more important question on the label is the declared dose: a 7.5 µg gummy carries the GB-authorised claim with no lab-test complication; a 5,000-10,000 µg high-strength product carries the lab-test interference risk.
Do vegans need biotin supplements?
Generally no. Biotin is widely distributed in plant foods — soybeans, sunflower seeds, sweet potato, oats, almonds, legumes, and yeast are all good sources, and gut bacteria contribute. A vegan diet is not a recognised risk factor for biotin inadequacy in adults eating a varied range of plant foods. Marketing aimed at vegans for "biotin for hair" is not based on a deficiency state. [6]
⚖️ The official position
What may lawfully be claimed about Biotin in Great Britain. This is a regulatory position, not an evidence grade.
A health claim is authorised in Great Britain.
“Biotin contributes to the maintenance of normal hair”
“Biotin contributes to the maintenance of normal skin”
“Biotin contributes to the maintenance of normal mucous membranes”
“Biotin contributes to normal energy-yielding metabolism”
“Biotin contributes to normal functioning of the nervous system”
“Biotin contributes to normal macronutrient metabolism”
“Biotin contributes to normal psychological function”
This claim is authorised for use in Great Britain under the GB Nutrition and Health Claims regulation. A product may carry it when it provides at least 15% of the UK NRV per recommended daily portion.
Authorised UK health claims
Verbatim from the GB Nutrition and Health Claims Register (Reg 432/2012 as assimilated in GB). A product can carry these claims when it provides at least 15% of the UK NRV per recommended daily portion.
7 authorised claims — show / hide
- "Biotin contributes to the maintenance of normal hair"
- "Biotin contributes to the maintenance of normal skin"
- "Biotin contributes to the maintenance of normal mucous membranes"
- "Biotin contributes to normal energy-yielding metabolism"
- "Biotin contributes to normal functioning of the nervous system"
- "Biotin contributes to normal macronutrient metabolism"
- "Biotin contributes to normal psychological function"
Camden guides citing Biotin
Editorial pieces from the Camden blog that reference Biotin. Each guide cites the evidence it draws on.
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Hair, skin, and nail health in healthy non-deficient adults
LimitedEvidencelimitedThe 2017 review of biotin for hair loss by Patel, Swink and Castelo-Soccio (Skin Appendage Disorders) found no high-quality randomised controlled trial evidence that biotin supplementation improves hair growth in healthy non-deficient adults. The clearest cases of biotin-responsive alopecia are in inherited biotin-handling disorders, acquired deficiency states (long-term anticonvulsant use, prolonged total parenteral nutrition without biotin, raw-egg-white diets), and infants. The authors propose that biotin supplementation should be reserved for documented deficiency rather than used as a routine cosmetic intervention. [10]
Brittle-nail syndrome (uncontrolled case series)
LimitedEvidencelimitedFloersheim 1989 (Z Hautkr) gave 71 patients 2.5 mg biotin daily; of 45 evaluable cases, 41 showed firmer nails after a mean 5.5 months. Hochman 1993 (Cutis) retrospectively reviewed 35 brittle nail patients on biotin and reported 22 (63%) clinically improved. Neither study had a placebo arm or randomisation. The signal is real enough to warrant the GB-authorised "maintenance of normal hair / skin" claim but not strong enough to support marketing biotin as a remedy for thinning hair or weak nails in unselected adults. [13,12]
Inherited biotinidase deficiency and holocarboxylase synthetase deficiency
StrongEvidencestrongThese are autosomal recessive disorders of biotin handling. Untreated, they cause seizures, hypotonia, developmental delay, alopecia, and a characteristic perioral and periorificial skin rash. Lifelong oral biotin (typically 5-20 mg/day) under specialist supervision prevents the picture and reverses many early features. Many UK regions screen for biotinidase deficiency at birth. This is a paediatric-metabolic clinical pathway, not a consumer-supplement story. [6]
Biotin interference with immunoassay-based blood tests
StrongEvidencestrongMany clinical immunoassays use the very strong streptavidin-biotin binding interaction as part of their design. Free biotin circulating in the patient's blood saturates this binding and falsifies the result — usually a falsely low value in sandwich-format assays and a falsely high value in competitive-format assays. The Avery 2019 review (Annals of Clinical Biochemistry) catalogues affected analytes including cardiac troponin, TSH, free T4, free T3, hCG, parathyroid hormone, 25(OH) vitamin D, ferritin, and many tumour markers. Elston 2016 (J Clin Endocrinol Metab) reported a case report and literature review of factitious Graves' disease driven by biotin supplementation falsifying thyroid panels. Favresse 2018 (Endocrine Reviews) published a detection algorithm for immunoassay interference. The FDA issued public safety communications in November 2017 and an updated communication in November 2019 specifically flagging the troponin-assay risk for missed heart attacks. [9,14,11,6]
Pregnancy biotin status
InsufficientEvidenceinsufficientMarginal biotin status appears more common in pregnancy than once thought. The clinical significance is uncertain: there are no randomised trials showing that routine biotin supplementation in pregnancy improves outcomes, and very high doses are unstudied for pregnancy safety. UK NHS guidance is to get biotin from a varied diet. Pregnancy supplementation should only be on advice of a midwife or GP. [6,1]
Safety
Biotin from food at the UK NRV (50 µg/day) is safe and necessary, and meeting it through a varied diet is the default position. The most important safety message about high-dose biotin (5,000-10,000 µg) is not toxicity — it is that megadose biotin interferes with many common blood tests for several days, including cardiac troponin (used to diagnose heart attack), TSH, hCG (pregnancy), and vitamin D. Stop high-dose biotin at least 48-72 hours before any blood test, longer if your lab instructs.
Talk to your pharmacist or GP first if you:
- You are scheduled for any blood test — cardiac troponin, thyroid TSH, hCG/pregnancy, vitamin D, parathyroid hormone, ferritin, or many tumour markers. High-dose biotin can falsify these results. Stop high-dose biotin at least 48-72 hours before the test, longer if your lab specifies.
- You are pregnant, planning pregnancy, or breastfeeding — pregnancy is not a context for high-dose self-medication and pregnancy is also a setting where the hCG-test interference matters.
- You are on dialysis — biotin handling differs and your renal team will guide supplementation.
- You take long-term anticonvulsants (phenytoin, carbamazepine, primidone, phenobarbital) — these have been reported to lower biotin status over years; supplementation is a clinical decision.
- Your hair, skin, or nails are changing — there are diagnosable medical causes (thyroid disease, iron deficiency, post-pregnancy telogen effluvium) that biotin will not fix.
- You are considering long-term high-dose biotin (≥5,000 µg/day) for any reason — discuss with your pharmacist or GP first.
Common side effects: Biotin is generally well tolerated. The systemic safety issue is not toxicity but immunoassay interference at high doses. Skin reactions and gastrointestinal upset are very rare.
Pregnancy and breastfeeding
The UK NRV for biotin is unchanged in pregnancy at 50 µg/day. Marginal biotin status appears more common in pregnancy than once thought; clinical significance is uncertain and routine megadose supplementation is not recommended. Speak to your midwife, GP, or pharmacist before starting any biotin supplement in pregnancy. The hCG immunoassay used in pregnancy testing can be affected by high-dose biotin — another reason megadose biotin is the wrong choice in pregnancy.
NRV unchanged; biotin is secreted in human milk. Routine megadose supplementation is not recommended. Discuss with a pharmacist or GP.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- Known hypersensitivity to biotin or any product excipient.
- Imminent immunoassay-based blood test where the lab has not been told that the patient is taking high-dose biotin (relative — pause biotin, do not pause investigations).
Drug interactions
- Phenytoin, carbamazepine, primidone, and phenobarbital — long-term use of these antiepileptics has been associated with reduced biotin status, possibly through accelerated biotin catabolism. Routine high-dose supplementation is a clinical decision; discuss with your prescriber (NIH ODS biotin fact sheet).
- Lipoic acid — competes for the same intestinal transporter at very high doses. Clinical relevance at typical supplemental doses is minimal.
- Antibiotics (long-term, broad-spectrum) — may reduce gut-bacterial biotin synthesis. The contribution of gut bacteria to overall biotin status in adults is small; clinical relevance is generally minor.
- All immunoassay-based laboratory tests — see the consumer summary. Not a drug interaction in the classical sense, but a clinically critical one.
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Biotin is generally very well tolerated at typical supplemental doses.
Rare side effects
- Mild gastrointestinal upset has been reported anecdotally at high doses.
- Allergic / hypersensitivity reactions to product excipients (rare).
- Acneiform skin reactions have been reported in case reports at megadose; the causal link is uncertain.
How to take it
- UK Reference Nutrient Intake
- 50 µg/day
- Typical supplemental range
- 7.5 µg per portion — the GB NHC threshold to carry the authorised hair / skin claim.
- Timing
- Any time of day. Water-soluble; food not required.
How to spot quality
Look for
- Form named explicitly as D-biotin (the active stereoisomer found in food and used in research).
- Microgram amount per serving stated on the label, alongside % NRV (UK NRV = 50 µg).
- GMP-certified manufacture; ideally third-party potency testing.
- A clear, prominent warning at any dose ≥1,000 µg that high-dose biotin can interfere with common blood tests (troponin, TSH, hCG, vitamin D, parathyroid hormone) and instructing users to stop biotin at least 48-72 hours before a blood test.
- Honest dose framing — 7.5 µg per portion is enough to carry the GB-authorised hair / skin claim. Megadose framing should be evidence-led, not marketing-led.
Red flags
- High-strength biotin (5,000-10,000 µg) marketed for hair growth without any warning about lab-test interference — this is the most common UK labelling gap.
- "10,000 µg potency" or similar marketing intensifiers without an evidence-based basis for the dose.
- Combination products that hide the per-ingredient biotin dose inside a proprietary hair-skin-nails blend.
- Megadose biotin stacked with collagen, shilajit, or undisclosed botanical blends marketed for hair regrowth — combination evidence is weaker than single-ingredient evidence and the lab-interference issue still applies.
- Marketing that frames biotin as a remedy for alopecia, a way to reverse thinning hair, or a metabolism booster for weight loss — none of these positions are GB-authorised.
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Collagen
Limited evidenceBeauty-cluster pairing — biotin + collagen support hair / skin / nails framework.
Biotin cofactor for keratinocyte fatty-acid synthesis; collagen peptide amino-acid substrate for dermal matrix. Complementary on beauty axis. UK Article 13.1 biotin hair / skin / mucous-membrane maintenance claims.
Evidence: UK Article 13.1 biotin claims authorised. [8]
Doses studied: 50-200 µg biotin (within UK NRV 50 µg) + 5-10 g/day hydrolysed collagen.
Zinc
Limited evidenceBeauty-cluster pairing — biotin keratinocyte FA + zinc keratinocyte zinc-finger transcription factors.
Biotin enzyme cofactor + zinc keratinocyte zinc-finger transcription. Different mechanisms; complementary on hair / skin / nails axis.
Evidence: Beauty-cluster co-formulation. [8,8]
Doses studied: 50-200 µg biotin + 10-15 mg zinc daily.
Selenium
Moderate evidenceHair / nails cluster — biotin + selenium UK Article 13.1 hair / nails maintenance claims.
Both UK Article 13.1 hair / nails maintenance authorised. Different mechanisms; complementary.
Evidence: UK Article 13.1 hair / nails claims for both. [8,8]
Doses studied: 50-200 µg biotin + 100-200 µg selenium daily.
Found in Camden: Purifera™ Selenium 200µg L-Selenomethionine 120 Capsules
Retinol (Vitamin A1, all-trans-retinol)
Limited evidenceBeauty-cluster oral adjunct — biotin contributes to keratinocyte fatty-acid synthesis; retinol drives gene-expression remodelling. Different mechanisms, complementary marketing framing.
Biotin (vitamin B7) is a coenzyme for the four mammalian carboxylase enzymes (acetyl-CoA carboxylase, propionyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, pyruvate carboxylase) that participate in fatty-acid synthesis, gluconeogenesis, and amino-acid catabolism. In keratinocytes, biotin-dependent fatty-acid synthesis contributes to ceramide and cholesterol synthesis for the stratum corneum lipid lamellae. Frank biotin deficiency produces dry, scaly skin, hair fragility, and brittle nails.
Topical retinol drives retinoid-receptor gene-expression remodelling — different axis. The combination is consumer-marketing-coherent (both feature in beauty bundles) without strong mechanistic synergy. UK Article 13.1 authorised claim "Biotin contributes to the maintenance of normal skin" supports the oral side; topical retinol has no UK authorised health claim. Camden's biotin covers the oral side including the high-dose biotin lab-test interference issue.
Evidence: Different mechanisms; no specific combination trial evidence. UK Article 13.1 biotin skin-maintenance claim authorised (gb-nhc:biotin); topical retinol photoaging trial evidence moderate. [8]
Doses studied: Topical retinol 0.2-0.5% evening + oral biotin 50-200 µg/day (within UK NRV 50 µg). Avoid high-dose biotin (>5000 µg/day) without flag-stop notice 72h before any blood test (lab interference issue per biotin).
Vitamin B5 (Pantothenic Acid)
Moderate evidenceB-complex cluster — B5 + B7 (biotin) carboxylase cofactor cluster.
B5 CoA component for fatty-acid synthesis; biotin carboxylase cofactor for fatty-acid synthesis (acetyl-CoA carboxylase). Mechanism complementary on fatty-acid synthesis + skin maintenance axes.
Evidence: UK Article 13.1 claims both. [8]
Doses studied: 6 mg B5 + 50-200 µg biotin daily.