Medik8 C-Tetra

If C E Ferulic is the clinical heavyweight, Medik8 C-Tetra is the sensible everyday choice. It uses 7% tetrahexyldecyl ascorbate, an oil-soluble vitamin C derivative that is more stable than pure L-ascorbic acid and, Medik8 says, less likely to sting or oxidise, so the formula stays potent for longer and suits people who found stronger serums irritating. The lightweight oil texture, cushioned with squalane and vitamin E, sinks in fast, leaves a subtle glow and layers happily under moisturiser and SPF. It will not deliver the same rapid, dramatic results as a high-percentage L-ascorbic acid serum, and 7% is a moderate dose, but as a stress-free daily antioxidant that most skin types tolerate, it is hard to beat. Medik8 also offers stronger C-Tetra Luxe (14%) and Advanced (20%) versions if you want to step up over time.