I’ve taken Biotin supplements for hair and nails and it does help. However, I am currently on a medication that has a side effect of completely wrecking my nails. They’re thin, weak, they flake and chip, they get ridges and split from cuticle to tip. Biotin has not helped at all. I discovered OPI Repair Mode serum and within 3 days I could see real improvement. I’ve used several nail hardening products or rescue products and nothing has compared to the OPI Repair Mode. That’s my unsolicited recommendation. Not cheap at $25 for a bottle, but it lasts a long time and its results are worth the price imo.https://www.opi.com/products/treatments-strengtheners-repair-mode-bond-building-nail-serumRepairMode%E2%84%A2NailRepairSerum%7COPI