Defend against premature skin ageing and achieve accelerated skin brightening with Medik8 C-Tetra Advanced, a next-generation combination of 20% vitamin C and skin barrier science.  Medik8 C-Tetra Advanced is a 20% Vitamin C Gel-Serum with Phyto Exosomes. Clinically proven to brighten skin and visibly improve wrinkles in 7 days with 0% barrier disruption, C-Tetra Advanced is engineered for high-performance visible brightening, skin smoothing, and daily antioxidant defence.