As a beauty editor and skincare obsessive, I’ve tested countless serums over the years – but not all are formulated equal. Brands often market with big claims, and most don’t live up to their flashy promises, particularly when it comes to vitamin C serums.
However, there’s one serum that has become a staple in my skincare routine: Medik8 C-Tetra advanced. Hardworking, effacious and gentle on skin, the serum dethrones all competition. This isn’t the only Medik8 formula I trust – I’ve sworn by the brand’s crystal retinal formula (was £69, now £55.20, Medik8.com) for years, and not a single retinoid serum has managed to dethrone it from its spot in my routine. It’s clear that the brand’s science-backed, effective approach to skincare – particularly its ‘CSA’ philosophy, which focuses on vitamin C, sunscreen and vitamin A – actually works.
That said, the brand’s best-selling C-Tetra serums – both the original (was £45, now £36, Medik8.com) and the luxe (was £60, now £48, Medik8.com) versions – didn’t quite hit the mark, as the oily consistency didn’t pair well with my skin. So, when I first got wind that Medik8 was launching a new ‘advanced’ iteration – which is not only more effective but also features an entirely different gel-like texture – I was fascinated to see if there would be any improvements.
According to Dr Bibi Ghalaie, cosmetic physician, founder and medical director at the Doctor Bibi Clinic, what makes this serum stand out is its potency and stability. It has 20 per cent tetrahexyldecyl ascorbate (a form of vitamin C), which is an impressive jump in concentration compared with the 7 per cent in the original C-Tetra, and 14 per cent in the C-Tetra luxe. “It’s rare to see such a powerful brightening treatment that also strengthens and supports skin health from within,” says Dr Ghalaie.
With this in mind, I’ve been on a mission to put the C-Tetra advanced serum to the test, having reviewed the formula for more than a month to give you the lowdown on everything worth knowing about this clever serum.
Read more: Best vitamin C serums, chosen by a beauty editor
How I tested
As directed, I’ve been using the C-Tetra advanced formula every day as part of my morning skincare routine, applying the serum on a freshly cleansed face, right after using my replenishing toner. I applied two to three pumps before gently massaging the formula in and following up with moisturiser and an SPF – I used the Tatcha dewy skin cream (£67, Spacenk.com) and the Kate Somerville hydraKate illuminating SPF 50 drops (£39, Johnlewis.com).
I applied the serum every morning over the course of four weeks (Denise Primbet)
To ensure a fair verdict, I haven’t swapped out any other steps in my routine for four weeks. I continued to use my usual skincare heroes, such as the Medik8 crystal retinal serum, which is my non-negotiable retinoid formula that I usually reach for as part of my night-time routine. I’ve also kept my supplement routine consistent, so I’d be able to pinpoint any changes or improvements as being due to the Medik8 vitamin C formula.
When testing the formula, I paid close attention to a number of factors, including consistency, scent, absorption, irritation and, most importantly, whether it actually ended up delivering the results I was hoping to achieve.
