Re: DIY Vitamin C Serum
I keep mine in the refrigerator & I usually finish the 1oz bottle in 3-4 weeks so haven’t actually dealt with it going “bad” (I use it on my neck/upper chest and often on my arms too). But if you put the serum in a amber dropper bottle, and store it in a dark/cool place (does not have to be a refrigerator)…it should last as least a few weeks I would think. You know it oxidized when you see the white color change…any hints of yellowish tint means it needs to be thrown away.