If storing your serum in the refrigerator isn’t an option, find a cool, dark place in your bedroom or another room where you can keep it.
Try keeping a handheld mirror near the place where you store your vitamin C serum so you can apply it there. If you apply your vitamin C serum in the bathroom, try to find a trick to remind yourself to put it back after you’re finished. For instance, you might want to hold the bottle the whole time you are applying the serum instead of sitting it on the counter.
This will effectively prevent half of your serum from being exposed to oxygen, helping it to last longer.
For most formulas, this usually happens after about 3 months at room temperature or 5 months with refrigeration, although the exact amount of time will vary between brands.
Look for serums made with ascorbic acid (AA), tetrahexyldecyl ascorbate (THDA), magnesium ascorbyl phosphate (MAP), or sodium ascorbyl phosphate (SAP). [6] X Research source You can find options online here and here.
Look for formulas made with ascorbyl glucoside, magnesium ascorbyl phosphate, and tetrahexyldecyl ascorbate.
If you can only find transparent bottles, transfer your new serum to an opaque bottle after you get home.
Since vitamin C serum expires after a few months, only buy what you think will use before the expiration date.
