Biotin is best known for hair, skin, and nails, though its actual job is broader: it helps metabolise fats, carbohydrates, and protein. Genuine low intake is uncommon, and where it occurs it's been associated with thinning hair, brittle nails, and skin rashes. Worth being honest that the "biotin for hair growth" reputation runs well ahead of the evidence for people who already get enough.
Adults need around 30 mcg a day, from eggs (especially the yolk), nuts, seeds, salmon, and sweet potato. There's no established upper limit.
One honest note: reliable data on how common low biotin intake is remains thin, and it's harder to pin down than the better-studied nutrients, so we'd treat any read on your intake here as rough guidance rather than a precise status.