How should I store my Vitamin C serum?

Vitamin C serums, especially those containing L-ascorbic acid, should be stored in a cool, dark location away from direct sunlight and heat. A cabinet, drawer, or even the refrigerator works well. If your serum turns orange or brown, it has oxidized and lost much of its potency. Serums in opaque or dark glass packaging oxidize more slowly than those in clear bottles.