Biotin for Hair Growth: What the Evidence Really Shows
What the evidence says about biotin for hair growth, the authorised UK claim, how much biotin you need and why you should tell your doctor before a blood test.
By the GUUDIES Editorial Team · Updated 25 October 2026 · Claims checked against the GB Nutrition and Health Claims Register; sources below.
Disclosure: GUUDIES sells a daily gummy pouch that contains biotin. We explain below why we do not describe it as a hair growth product.
The short answer: biotin for hair growth is well supported only in people who are actually short of biotin, which is rare in people eating a normal diet. The authorised claim in Great Britain is that biotin contributes to the maintenance of normal hair and normal skin, not that it makes hair grow faster or thicker.
What Is Biotin?
Biotin is vitamin B7, one of the B vitamins. It helps enzymes in the body break down fats, carbohydrates and protein. It is found in foods such as eggs, meat, fish, seeds, nuts and some vegetables. The nutrient reference value (NRV) used on GB labels is 50µg a day.
The authorised GB health claims for biotin include that it contributes to the maintenance of normal hair and the maintenance of normal skin. There is no authorised claim that biotin promotes hair growth, stops hair loss or thickens hair.
Does Biotin Help Hair Grow?
The evidence splits into two groups.
| People with low biotin | People with normal biotin | |
|---|---|---|
| How common | Rare; higher risk with some genetic conditions, long-term heavy drinking, and during pregnancy and breastfeeding | Most adults eating a normal mixed diet |
| Signs | Thinning hair, scaly red rash around the eyes, nose and mouth, brittle nails | None linked to biotin |
| Evidence for supplements | Correcting a deficiency helps hair and skin | Limited to a few case reports and small studies |
A 2017 review in Skin Appendage Disorders looked at the published cases where biotin was used for hair and nails. It found biotin was only shown to help when an underlying biotin deficiency had been established (Patel et al., 2017). The US National Institutes of Health reaches a similar view: claims for hair, skin and nails in healthy people are supported, at best, by a few case reports and small studies, and better studies in healthy people are needed (NIH ODS).
Why Hair Thins: Common Causes Biotin Will Not Fix
Hair thinning and shedding have many causes, and most are not about biotin:
- Genetics: male and female pattern hair loss.
- Stress or illness: heavy shedding a few months after a fever, operation, major stress or giving birth.
- Low iron or other nutrient gaps: worth checking with a GP blood test, especially with heavy periods.
- Thyroid problems and some medicines.
- Rapid weight loss or a very restricted diet.
If your hair is thinning noticeably, falling out in patches, or you have other symptoms, see your GP first. A supplement is not a substitute for finding the cause.
How Much Biotin Is Enough?
The NRV is 50µg a day, and a varied diet usually covers it. Many biotin supplements contain thousands of micrograms (several milligrams), far above what the body needs. More is not better: biotin is water soluble, and there is no evidence that very high doses improve hair in people who are not deficient.
Biotin Can Affect Some Blood Tests
This is the part most biotin marketing leaves out. Biotin can interfere with certain laboratory tests that use biotin in their chemistry. The US Food and Drug Administration has warned that biotin in supplements can significantly interfere with some lab tests, and it continues to receive reports of falsely low results for troponin, a test used to help diagnose heart attacks (FDA). The NIH notes that a single 10mg dose interfered with thyroid function tests taken within 24 hours, and case reports describe people wrongly appearing to have an overactive thyroid while taking high-dose biotin (NIH ODS).
Whatever dose you take, tell your doctor or the person taking your blood that you take biotin, including in a multivitamin or hair, skin and nails product. They can advise whether to pause it before a test.
What to Look For in a Biotin Supplement
- A dose in micrograms you can see on the label, with its % NRV.
- No promises of hair growth, thicker hair or stopping hair loss. These are not authorised claims.
- A sensible dose rather than the biggest number.
- A format you will take every day.
If you are pregnant, breastfeeding, taking medication or have a medical condition, check with your GP or pharmacist before starting any supplement.
Where GUUDIES Fits
GUUDIES is one daily pouch of six pectin-based gummies for adults. Biotin appears in two of them: the Marine Collagen gummy contains 100µg of biotin (200% NRV) alongside 200mg of hydrolysed marine collagen peptides, and the Daily Greens+ gummy adds 30µg (60% NRV). That is 130µg a day in total, a modest amount compared with many single biotin products. Biotin contributes to the maintenance of normal hair and normal skin. Daily Greens+ also contains vitamin C, which contributes to normal collagen formation for the normal function of skin. There is no authorised health claim for collagen itself.
Five of the six gummies are vegan; Marine Collagen contains fish. Read more about the biotin in GUUDIES.
Common Questions
Does biotin make hair grow faster?
There is no good evidence that biotin speeds up hair growth in people who are not deficient. The authorised claim is that biotin contributes to the maintenance of normal hair.
How long does biotin take to work for hair?
If you are genuinely short of biotin, changes follow the hair growth cycle and take months. If you are not deficient, you may not see any change.
How much biotin should I take for hair?
The NRV is 50µg a day. Higher doses have not been shown to help people with normal biotin levels.
Can biotin affect blood test results?
Yes. Biotin can interfere with some lab tests, including thyroid and troponin tests. Tell your doctor you take it before any blood test.
Is biotin safe to take every day?
Biotin is water soluble and no toxicity has been seen at high intakes, but the lab test issue matters. Speak to a pharmacist if you take medication.
Sources
- NIH Office of Dietary Supplements, Biotin fact sheet for health professionals: ods.od.nih.gov
- Patel DP, Swink SM, Castelo-Soccio L. A Review of the Use of Biotin for Hair Loss. Skin Appendage Disorders, 2017: PMC
- US Food and Drug Administration, Biotin interference with troponin lab tests: fda.gov
- GB Nutrition and Health Claims Register: gov.uk
Related Reading
Hair, Skin and Nails Gummies Guide · Collagen Gummies and Skin · Marine vs Bovine Collagen · Biotin in GUUDIES
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