Biotin may be the only vitamin that many people know mainly from shampoo bottles. Also called vitamin B7, it is a water-soluble vitamin that helps enzymes process fats, carbohydrates and proteins. Its fame comes from hair and nails, but the science behind that reputation is thinner than the advertising suggests.
Do most people need more?
True biotin deficiency is uncommon in people who eat a varied diet. The NHS notes that biotin is found in a wide range of foods, if only at low levels, and that bacteria living naturally in the bowel also make it, so it is unclear whether most people need any extra from their diet at all. Deficiency is seen in certain situations, including some rare inherited conditions, and it can cause thinning hair, rashes and brittle nails. Everyday sources include eggs, liver, nuts, seeds and legumes.
What the research says about hair and nails
A review published in the journal Skin Appendage Disorders in 2017 searched the medical literature for evidence on biotin and hair or nail growth. It found 18 case reports, and in every one of them the patient had an underlying condition affecting hair or nails, such as a deficiency or brittle nail syndrome, and improved with biotin. The authors found no good evidence that biotin helps hair or nails in healthy people, and they described such cases of deficiency as uncommon. So in people who are truly deficient, a doctor can address the shortage and symptoms may improve. For everyone else, results cannot be promised, and hair changes slowly in any case.
The lab test problem
This is the part many people have not heard. High biotin intake can interfere with certain laboratory tests that rely on biotin in their design. Depending on the test, results can come out falsely high or falsely low. The US Food and Drug Administration has received reports of biotin causing falsely low results on troponin tests, which help diagnose heart attacks, and it keeps a public list of troponin assays that remain subject to this interference. Tests that may be affected include:
- Troponin, used to help diagnose heart attacks
- Thyroid hormone tests
- Some other hormone and immunoassay tests
The consequences can be serious if a wrong result leads to a wrong decision. Always tell your doctor and the laboratory if you take biotin, including in multivitamins or hair products. Ask whether you need to stop before a blood test, and for how long.
How much is too much
The NHS says there is not enough evidence on the effects of high daily doses of biotin supplements, and advises that 0.9 mg or less a day from supplements is unlikely to cause harm. Many hair products contain far more than that, which is one reason the lab test issue matters.
When to see a doctor about hair or nails
Hair loss has many causes, among them low iron, thyroid problems, hormonal changes, stress, illness, childbirth and some medicines. A doctor can arrange the right tests. Go sooner if hair falls out suddenly or in patches, or if nails change colour or shape. If you are pregnant or breastfeeding, or take regular medication, consult your doctor or pharmacist before using supplements.
A sensible takeaway
Eat enough protein, iron-rich foods such as lentils and red meat, and a wide variety of plants. Treat hair gently, and be patient. Food, sleep and medical care come first; a supplement is optional.
Sources
- A Review of the Use of Biotin for Hair Loss · Skin Appendage Disorders
- Biotin Interference with Troponin Lab Tests - Assays Subject to Biotin Interference · US Food and Drug Administration (FDA)
- B vitamins and folic acid · NHS
This article is general health information for educational purposes and is not medical advice. It does not promote any product. Talk to your doctor or pharmacist before starting a supplement, especially if you are pregnant, breastfeeding, have a health condition or take medication.