L-Ascorbic Acid Stability: Why Your Vitamin C Serum Keeps Turning Orange
22 July 2026 10 min read 683 views 0
L-ascorbic acid is the most potent form of vitamin C, but it oxidises easily, so packaging and storage matter as much as concentration.
Key takeaways
- L-ascorbic acid is the most researched form of vitamin C but oxidises easily with light, air and heat exposure.
- Effective concentrations generally sit between 10 and 20 percent at a low pH of around 3.5.
- A serum that has darkened to amber, brown or orange has likely lost much of its potency.
- Opaque, airless packaging and cool, dark storage meaningfully extend a product's usable life.
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