Biotin (Vitamin B7)
Biotin deficiency is rare: gut bacteria make some, and most diets have plenty. The bigger problem today is the opposite: high-dose biotin supplements for hair and nails can give falsely high or low results on some blood tests, including thyroid and heart tests.
Who becomes deficient
- Biotinidase deficiency: an inherited condition picked up by newborn screening in Australia
- Eating lots of raw egg whites over months (a protein called avidin binds biotin; cooking destroys it)
- Long-term use of some anticonvulsants
- Long-term tube or intravenous feeding without biotin, heavy alcohol use, malabsorption
Symptoms
- Thinning hair, sometimes loss of eyelashes and eyebrows
- A red, scaly rash around the eyes, nose and mouth
- Brittle nails
- Low mood, tiredness, tingling; seizures and developmental problems in babies with biotinidase deficiency
Taking biotin? Tell whoever orders your blood tests. High-dose biotin (often 5–10 mg in hair, skin and nail products) can make thyroid, hormone and troponin (heart attack) tests wrong. Ask whether to stop it for a few days before testing.
Hair and nails
- Biotin only helps hair and nails if you’re actually deficient, which is rare
- In people with normal levels, there’s no good evidence it improves hair loss or nail strength
- Common causes of hair thinning include iron deficiency, thyroid problems, stress and genetics: worth checking first
Biotin gummies grow one thing reliably: the supplement industry.
Treatment
- Biotin supplements correct deficiency quickly
- Babies with biotinidase deficiency take biotin for life and usually do very well
- Cook your eggs
Food sources
- Cooked eggs (especially the yolk), liver and meat
- Nuts, seeds and legumes
- Sweet potato, mushrooms and avocado
Weird history
- Biotin deficiency was first seen in rats fed raw egg whites, which gave them “egg-white injury”: hair loss and dermatitis
- It was once called vitamin H, from the German words for hair and skin (Haar and Haut)
Common questions
Does biotin help hair growth?
Only if you’re deficient, which is rare. In people with normal levels there’s no good evidence it helps hair loss.
Can biotin affect blood tests?
Yes. High-dose biotin can make some thyroid, hormone and troponin (heart) tests falsely high or low. Tell your doctor and ask whether to pause it before blood tests.
What causes biotin deficiency?
Rarely: inherited biotinidase deficiency (found on newborn screening), eating many raw egg whites, some anticonvulsants, or long-term tube or IV feeding.
Helpful resources
- Nutrient Reference Values for Australia and New ZealandOfficial daily intake targets. Free.
Evidence and more information
- Dasgupta A et al. Immunoassay design and biotin interference (Adv Clin Chem 2022)
- NIH Office of Dietary Supplements: Biotin
maladywise.com/biotin/