Biotin
Raw egg whites block it from absorbing. Cooked eggs don't have the same effect.
Biotin supports the enzymes that metabolise fat, carbohydrate, and protein, and it is best known to the public as a hair, skin, and nail supplement, though the evidence for that specific benefit in people who are not deficient is limited. Raw egg white contains a protein called avidin that binds biotin tightly and blocks its absorption; cooking denatures avidin and removes the effect, which is why the old advice about raw eggs and biotin deficiency is genuinely accurate rather than a myth. There is only one supplemental form in practical use, d-biotin, and no established upper limit.
Reference values
Daily reference values from official nutrition authorities. These are population reference figures, not personal recommendations.
| RDA | Upper limit | Source |
|---|---|---|
| 50 mcg | No UL set | UK |
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| d-biotin | Typical | Either | Either | Likely |
Stack Almanac totals your biotin across every supplement you log, including hair, skin, and nail formulas that often carry doses far above the 50mcg reference intake.
Track your Biotin in Stack Almanac
Last reviewed: 2026-07-08. Reference values are adult-general RDAs from UK. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.