Medik8 C-Tetra™

C-Tetra is widely regarded as one of the best vitamin C serums for sensitive skin. It uses tetrahexyldecyl ascorbate — a stabilised, lipid-soluble form of vitamin C that delivers powerful antioxidant benefits with virtually no irritation. In an independent consumer study conducted over 4 weeks on 52 participants with sensitive skin, users reported visibly brighter, more radiant skin in just 7 days.

C-Tetra contains 7% stabilised vitamin C and is the ideal starting point for those new to vitamin C or with sensitive skin. C-Tetra Luxe contains 14% vitamin C — double the concentration — and is enriched with squalane, maracuja oil, and red ginseng for enhanced brightening and deeper nourishment. Both use the same gentle, stabilised form of vitamin C (tetrahexyldecyl ascorbate).

Yes — in fact, Medik8 actively recommends it. Their CSA Philosophy champions vitamin C plus sunscreen in the morning and vitamin A (retinol/retinal) at night. This proven combination delivers maximum age-defying results. Simply apply C-Tetra each morning and your chosen vitamin A product each evening.

Thanks to its exceptionally stable formulation, C-Tetra remains potent and effective for 6 months after opening. Traditional vitamin C serums using L-ascorbic acid can degrade rapidly when exposed to light, heat, or air, but C-Tetra's tetrahexyldecyl ascorbate formula maintains its strength from the first drop to the last.

Yes. Vitamin C is clinically recognised for its ability to visibly brighten uneven skin tone and reduce the appearance of dark spots. C-Tetra's stabilised vitamin C works to promote a more even, radiant complexion with consistent daily use. For more targeted pigmentation concerns, you may wish to consider C-Tetra Luxe with its higher 14% concentration.

It is normal for an active antioxidant serum to vary in colour from batch to batch, and most antioxidant serums will darken slightly over time due to exposure to air. This is a natural process and does not affect the efficacy of the product or its ingredients. C-Tetra's stabilised formula ensures it remains effective throughout its shelf life.

Apply C-Tetra every morning after cleansing. If you use water-based serums or toners, apply those first, then follow with C-Tetra. After the serum has absorbed, apply your moisturiser and always finish with a broad-spectrum sunscreen. Vitamin C works best during the day as it provides antioxidant protection against environmental stressors like UV rays and pollution.

C-Tetra is suitable for all skin types, including the most sensitive. Its gentle, non-irritating formulation makes it an excellent daily vitamin C serum whether you have dry, oily, combination, or sensitive skin. The jojoba oil base provides lightweight nourishment without clogging pores, making it comfortable for everyday use.

As a cosmetics company, Medik8 are unable to provide product advice in relation to medical conditions such as pregnancy or breastfeeding. They recommend discussing the ingredients with your GP or midwife before use. As general guidance, this product does not contain any ingredients which Medik8 would recommend avoiding during pregnancy, unless advised by your doctor.