How many biotin pills can a teenager take?!
Question: How many biotin pills can a teenager take?
It sounds like your stylist has the right intention in mind, but it's not an automatic correlation. What I mean is that Biotin is one of the ingredients that the body uses to create new hair cells (as well as skin and nails), but that doesn't mean you'll automatically get thicker hair from it. A couple reasons would be because Biotin is just one of the ingredients for healthy hair (along with Silica, MSM, and L-Cysteine among others), but the cause of the thin hair would be the other major contributing factor... if it's a genetic issue, side effect from a drug, stress, or some other thing that's causing your hair to thin, the Biotin won't help anywhere near as much as you'll want it to.
With all that being said, 5 mg daily is the normal adult dosage and you should be just fine with that dosage... Biotin is water soluble so whatever your body doesn't need will be excreted.
Also to note, this is only going to help the hair cells that are being created now... what's already grown out is effectively dead cells so they won't be affected by better nutrition internally. Because of that, it may take a month or two to notice the difference in your roots and it'll take a few years for that healthy new hair to grow from nothing to a foot long or more. It's not fast-acting, but no hair supplements are... it does help to promote healthier hair, though. Good luck and I hope I helped!
Health/nutrition classes, personal experience, and personal research in my role as a Product Specialist for a vitamin company
Don't take anything on your hairdressers advice, see your Doctor and go by what they say.