Too strong for sensitive skin?

I would try looking up what the brand says in their website about this product if you really want it. One cool thing about how The Ordinary works is the regiment quiz (they give you a full am and pm routine based on your answers) and how much depth their description provides

As little as possible!! I have a very sensitive skin too and I tried the ordinary naicinamide 10% serum and my biggest mistake was using it daily when I should’ve used it only 1-2x a week. The result of my carelessness destroyed my skin barrier. Thought it won’t be that bad if you don’t use it too often, please be careful!!

Worth a shot! I love a lot of the stuff from the ordinary.

Don't worry I'm also a sensitive skin girl with combination I use niacinamide all time it improves a lot

Like @imecat said I’d use as little as possible even after patch testing. And in general the recommended amount of Niacinamide for effectiveness is 1-5% above that is superfluous and over zealousness that brands do to that can diminish the formulation and overall is a recipe for inducing unnecessary sensitivity.