Biotin Dosage: How Much You Really Need and What Happens If You Take Too Much

When people talk about biotin, a B-vitamin that supports skin, hair, and nail health. Also known as vitamin B7, it’s one of the most popular supplements sold today—mostly because of claims that it makes hair grow faster and nails stronger. But here’s the thing: most people don’t actually need extra biotin. Your body makes plenty of it through gut bacteria, and it’s in plenty of everyday foods like eggs, nuts, and spinach. So why are so many taking high-dose pills? The truth is, the hype often outpaces the science.

Biotin deficiency, a rare condition caused by genetic disorders, long-term antibiotic use, or eating raw egg whites daily. It can lead to thinning hair, skin rashes, and even neurological issues. But if you’re eating a normal diet, you’re almost certainly not deficient. On the flip side, biotin supplements, often sold in doses of 5,000 to 10,000 mcg. are way above the recommended daily intake of 30 mcg for adults. Taking that much won’t magically make your hair thicker—it just means you’re peeing out most of it. Worse, high doses can mess with lab tests. Some thyroid and heart tests give false results when you’re on high-dose biotin, which could lead to misdiagnosis. The FDA has warned about this, and doctors now ask patients if they’re taking biotin before running blood work.

There’s one real medical use for high-dose biotin: treating rare inherited metabolic disorders like biotinidase deficiency. Outside of that, there’s no solid proof that mega-doses help healthy people. A few small studies suggest mild benefits for brittle nails, but nothing conclusive for hair growth. If you’re considering biotin, start with food. If you still want a supplement, stick to 1,000–3,000 mcg max—and talk to your doctor first. You’ll find real stories below about what actually worked (and what didn’t) for people trying biotin for hair, skin, or energy. No fluff. Just what happens when you take it—and what to watch out for.