Skin, hair and nails
What the NHS, NICE and the British Association of Dermatologists say about biotin, collagen, zinc, iron and other supplements sold for skin, hair and nails.
The NHS says too much vitamin A or selenium could be harmful. Hair loss has many causes: the British Association of Dermatologists says a blood test may rule out iron deficiency, and the NHS recommends iron tablets when a blood test shows a low red blood cell count. NICE's summary for GPs says food supplements such as evening primrose oil have not been adequately assessed in trials for eczema. Doctors writing for Harvard Health say there is not enough proof that collagen changes skin, hair or nails.
NHS: See a GP if you are worried about hair loss. They may be able to tell what is causing it; see them before going to a commercial hair clinic.
Each line below is a short summary of what the named source says, with a link to read it in full. None of it is medical advice.
Advised
Iron
A mineral found in red meat, beans, nuts, dried fruit and fortified breakfast cereals.
- British Association of Dermatologists: A blood test may rule out causes of hair loss such as iron deficiency.
- NHS: Iron tablets are recommended if a blood test shows a low red blood cell count.
Also covered by NHS.
Limited evidence
Collagen
A structural protein in skin, tendons, cartilage and bones; supplements are peptides from fish, cattle, pigs or chicken.
- Harvard Health Publishing: Not enough proof that collagen pills or drinks change skin, hair or nails.
- Cleveland Clinic: Many studies are funded by the supplement industry, or their authors have ties to it.
No good evidence
Things to check
- MHRA: High biotin intake may give falsely high or low thyroid test results, so doctors should ask about it.
- NHS: Taking 0.9mg or less of biotin a day in supplements is unlikely to cause any harm.
- NHS: Do not take more than 25mg of zinc a day in supplements unless a doctor advises it.
- NHS: Too much selenium causes selenosis, which in its mildest form can lead to loss of hair and nails.
- NHS: Keep vitamin A from food and supplements to 1.5mg a day; if you eat liver weekly, take none in supplements.
- NHS: Do not take cod liver oil or supplements containing vitamin A when pregnant; always check the label.
- Harvard Health Publishing: People prone to gout, or told to limit protein, should not use collagen supplements or drinks.
- NHS: Keep iron tablets out of the reach of children: an overdose of iron in a young child can be fatal.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Sources
- Hair lossCommon causes of hair loss, when to see a GP, and the treatments available.
- Telogen effluviumA common type of hair shedding: its causes, how it is diagnosed, including blood tests, and self-care.
- Iron deficiency anaemiaSymptoms, including hair loss and nail changes, the GP blood test, iron tablets and diet.
- B vitamins and folic acidEach B vitamin, including biotin: where it comes from, how much people need, and how much is safe.
- Biotin: Fact Sheet for ConsumersHow much biotin people need, food sources, the evidence on hair, skin and nails, and lab tests.
- MHRA Safety Roundup: May 2025The medicines regulator's monthly safety summary, including biotin and thyroid blood tests.
- Considering collagen drinks and supplements?Two dermatologists on the evidence for collagen drinks and supplements for skin, hair and nails.
- Collagen: What It Is, Types, Function & BenefitsWhat collagen is, how the body makes it, and the research on collagen supplements.
- Vitamins and minerals - OthersOther minerals, including zinc and selenium: how much people need and how much is safe.
- Eczema - atopic: Scenario: Mild eczemaNICE's summary for GPs on managing eczema, including diet, supplements and complementary therapies.
- Vitamin AWhere vitamin A comes from, how much adults need, and the risks of too much.
- Pregnancy vitamins and supplementsSupplements to take when trying for a baby and in pregnancy, and ones to avoid.
Sources checked 28 September 2026. Prices checked 20 October 2026, ranked purely by price per dose. Which sources these pages use.