Does biotin shampoo get into your bloodstream? What is put on hair only enters your body through scalp or skin, not the hair shaft so it’s really tiny in amount. Finally, biotin placed on your hair will not promote growth, as it does not enter your body through the hair shaft, which is essentially dead.
Will biotin affect thyroid levels? Most commonly, biotin use can result in falsely high levels of T4 and T3 and falsely low levels of TSH, leading to either a wrong diagnosis of hyperthyroidism or that the thyroid hormone dose is too high.
What are the symptoms of too much biotin? Biotin supplements can cause problems if you take too much. Side effects can include skin rashes, digestive upset, problems with insulin release, and kidney problems. As with any supplement, the safety of long-term or high-dose use isn’t known.