Biotin for hair: what the dose and the evidence say

Wooden comb and hair tie beside eggs, sunflower seeds and walnuts — AI-generated illustration · NutriMetrics

Quick answer

The NHS says 0.9 mg (900 µg) or less a day of biotin from supplements is unlikely to cause harm. Many hair products give 5,000–12,000 µg, far above that.
The reference intake on labels is 50 µg a day. Hair products often contain 5,000–12,000 µg, 100 to 240 times as much.
Biotin deficiency is rare. Evidence for hair, skin and nails in people without deficiency comes from case reports and small studies.
High doses can cause falsely high or low results in some blood tests, including thyroid and troponin tests. Tell your GP and the lab.
The authorised claim covers maintenance of normal hair and skin, not hair growth or stopping hair loss.

Key numbers

UK figure for supplements (NHS): 0.9 mg (900 µg)/day or less; Unlikely to cause harm.
Reference intake on labels (NRV): 50 µg/day
Adequate intake, adults (EFSA): 40 µg/day
Typical "hair" product: 5,000–12,000 µg/day
Safe upper level: Not set; No toxicity seen, but lab-test interference is real.
Minimum for an authorised claim: 7.5 µg per daily dose

What these terms mean: NRV upper levels (NHS, EFSA) maximum levels by country daily dose

How to choose

Ask why your hair is thinning first: iron deficiency, thyroid problems, hormones and stress are far more common causes than low biotin.
If you still want biotin, a modest dose gives the same authorised claim as a mega-dose; more is not better.
In biotin + zinc + selenium combinations, check the zinc: the NHS says no more than 25 mg a day from supplements, and Germany's BfR suggests at most 6.5 mg per daily dose.
Gummies often contain sugar and less precise doses than tablets.
Before any blood test, tell your GP you take biotin.

Typical biotin products compared

Type	Typical biotin per day	Good to know
Plain biotin tablets	Often 5,000–10,000 µg	100–200 times the reference intake
Biotin + zinc + selenium	Often 5,000–12,000 µg	Zinc and selenium have their own hair and nail claims; check the zinc dose
Gummies	Often 5,000–10,000 µg	Usually contain sugar; dosing less precise
B complex or multivitamin	Tens to a few hundred µg	Covers needs if you are not deficient

What the evidence says

Biotin is found in eggs, nuts, seeds, liver and many other foods, and severe deficiency has never been reported in healthy people eating a normal mixed diet, according to the US National Institutes of Health. The claims for hair, skin and nails in healthy people rest on case reports and a few small studies, mostly in children with specific conditions.

That makes biotin a weak first choice for thinning hair. Low iron is a more common, testable cause: see iron and tiredness. If you do buy biotin, a moderate dose carries the same authorised claim and avoids lab-test problems.

What the label may legally claim

Authorised claims (GB and EU registers)

Contributes to the maintenance of normal hair and normal skin
Contributes to the maintenance of normal mucous membranes
Contributes to normal energy-yielding metabolism, macronutrient metabolism, nervous system and psychological function (all from 7.5 µg per daily dose)

Not authorised in GB or the EU

Hair growth or stopping hair loss
Thicker hair
Faster-growing or stronger nails

How health claims work (UK & EU): health claims

Products we have checked

Label data checked by NutriMetrics for products sold in Spain and Germany. UK product checks are next. Sorted alphabetically, not ranked.

Checked: 20 Oct 2026
Product	Per daily dose	Sold in	Label
Aldous Biotina Complex 12.000 µg + Zinc + Selenio + D3 + E1 tablet a day Contains 50 µg (2,000 IU) of vitamin D a day: count it if you also take vitamin D.	Biotin: 12,000 µg Zinc: 15 mg · citrate Selenium: 60 µg · sodium selenite Vitamin D3: 50 µg	Spain	Source
NatuGena Biotin, Zink & Selen1 tablet a day Zinc 10 mg is above Germany's BfR guidance of 6.5 mg per daily dose.	Biotin: 10,000 µg Zinc: 10 mg Selenium: 50 µg	Germany	Source
Vitamaze Biotin 10.000 µg + Zink + Selen1 tablet a day Zinc 10 mg is above Germany's BfR guidance of 6.5 mg per daily dose.	Biotin: 10,000 µg Zinc: 10 mg · gluconate Selenium: 50 µg · sodium selenate	Spain · Germany	Source

Who should be careful

Blood tests: high-dose biotin can interfere with tests that use biotin–streptavidin technology, including some thyroid and heart (troponin) tests.
Hair loss that is sudden, patchy or heavy needs a doctor, not a supplement.
Pregnancy: use a prenatal supplement with normal amounts rather than high-dose biotin.

FAQ

Does biotin make hair grow?

Only if you are deficient, which is rare. In people without deficiency, the evidence comes from case reports and small studies. The authorised claim is limited to maintaining normal hair.

How much biotin should I take?

The reference intake on labels is 50 µg a day and EFSA's adequate intake for adults is 40 µg. Most people get enough from food. No upper level has been set, but high doses can distort lab tests.

Does biotin affect blood tests?

Yes. High doses can give falsely high or low results in some assays, including thyroid and troponin tests. The US FDA has warned about this repeatedly.

Sources

Information only, not medical advice. No product on this page is a paid placement.