Biotin -

The FDA has warned that high biotin doses can interfere with critical blood tests, including those for heart attacks (troponin), thyroid function, and pregnancy. User Experience Summary A Review of the Use of Biotin for Hair Loss - PMC

It is effective for treating rare biotinidase deficiencies or conditions like "uncombable hair syndrome". biotin

Scientific reviews indicate that biotin is highly effective for those with a deficiency, but there is little clinical proof that it improves hair or nail health in healthy individuals. The FDA has warned that high biotin doses