No prob! http://www.iherb.com/NutriBiotic-Ascorbic-Acid-Crystalline-Powder-16-oz-454-g/24191 is the brand of C I use. The pantothenic acid brand shouldn’t matter. Yes the C can cause minor stomach upset if taken on an empty stomach. Yeah the D is important for everything, including the immune system so that will be a good test to have again.