how did you know when your niacinamide expired??

That happens with high concentration Niacinamide. Its normal and safe to use still, as long as its still in PAO. I would say changes in color and if there is scent I would be suspicious.

Did you open it 9 months after getting it or have you used it for 9 months? This product is good to use for 12 months after opening and there is also an expiration date on the bottle. It has 10% niacinamide which can explain the crusting, but if the product inside the bottle look good you can use it.

That seems normal with products containing high concentrations of Niacinamide. Mine has the same thing and it's long before the expiry date and PAO.

No worries, it's pretty normal with niacinamide and that's how it also looked with my niacinamide bottle from The Ordinary. In checking the shelf life of a product, you can look over the box or the container of the product. You'll see a tub/shell life icon that basically tells you how long it's supposed to be used once opened. Hope this helps 😊

Usually high levels of niacinamide are like that