Is using The Ordinary Niacinamide + Garnier Vitamin C serum at the same time okay?

you dont need the niac serum , the garnier vit c serum already contains niacinamide :) !

As the ordinary niacinamide is labeled not to use them with vit c so it's better to use them in separate routine

well both niacinamide and vit c are quite strong actives but on the other hand most people tolerate niacinamide is very well. i would suggest trying to adjust it slowly and if you won’t see any bad reaction feel free to continue using both at the same time.

You can use Niacinamide serum at day time and the Garnier serum at night time. Those two are both active ingredients which may cause an irritation to your skin if you combine those them at same time.

I think you should separate them.. Use the vit C in the morning and the Niacinamide at night. So your skin won't get irritated