[header] How to store vitamin c serum [title] Close the lid tightly after each use. [step] Since oxygen breaks down vitamin c, you should make sure you close the lid tightly each time you use it, and try to limit how long you leave the bottle open. [title] Store your vitamin c serum in the fridge. 
[step] Vitamin c has an extremely short shelf life because it oxidizes, or breaks down when it's exposed to oxygen. Your fridge is a great place to store vitamin c serum, because the refrigeration will help delay the oxidation process longer than storing it at room temperature.