As a skincare-obsessed beauty editor, I’ve tested more than my fair share of serums. Although each formula claims to be exceptional in its own right, not all of them have managed to live up to their bold promises, particularly when it comes to vitamin C serums.
But the newly launched Medik8 C-Tetra advanced serum has already become a staple in my routine. I’ve often relied on Medik8 to deliver truly hardworking formulas. In fact, I’ve sworn by the brand’s crystal retinal formula (£69, Medik8.com) for the better part of the past three years, and not a single retinoid serum has managed to dethrone it from its spot in my routine. I’m already a fan of the brand’s science-backed, effective approach to skincare, particularly its ‘CSA’ philosophy, which focuses on vitamin C, sunscreen and vitamin A.
That said, the brand’s best-selling C-Tetra serums – both the original (£42, Medik8.com) and the luxe (£59, 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.
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).
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.
Why you can trust IndyBest reviews
Denise Primbet has been a journalist for more than five years, and has specialised in beauty for the past three years. She knows her niacinamide and tranexamic acid from her vitamin C and can tell which retinoid-infused formula will work by just glancing at the ingredient list. As for Medik8, she’s reviewed every single formula the brand’s produced, so she’s well placed to review its latest serum.
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Medi8 C-Tetra advanced
Key ingredients: 20 per cent stabilised vitamin C (tetrahexyldecyl ascorbate), phyto exosomes, acetyl zingerone, hyaluronic acid, n-acetyl glucosamine
Suitable skin types: All, particularly mature skin
Cruelty-free and vegan-friendly: Yes
Why we love it
- Features a highly concentrated (and stable) form of vitamin C
- Offers youth-boosting benefits
- Has a nice milky, gel-like consistency that’s not at all greasy
- Didn’t cause any sensitivity (even on my rosacea-prone sensitive skin)
Take note
- Expensive
- May not work for those sensitive to fragrance
Unlike the brand’s luxe and standard iterations, the advanced serum comes in a bottle with a pump, rather than a pipette. I loved the consistency and texture, which was reminiscent of a milky gel-like serum. My dry and sensitive skin soaked it up immediately, and I was pleasantly surprised that, even with my mild rosacea, this serum didn’t result in any irritation, which is not usually the case with most vitamin C serums I’ve tried.
What impressed me most, though, was the undeniable ‘lit from within’ glow that followed. Even after one use of this serum, my skin had that coveted post-facial look. In fact, later that same day, one of my friends quizzed me as to what had left my complexion so dewy and radiant. My hydration levels were visibly boosted, too.
By the end of the day, my skin still felt (and looked) well cared for, and my usually noticeable dry patches were practically undetectable. The serum also layered beautifully with the rest of my skincare and didn’t cause any pilling underneath makeup. While I enjoyed the uplifting citrusy scent (which doesn’t smell artificial), those more sensitive to fragrance may find it a tad overwhelming.
During my first week of using this product, I was dealing with yet another Polycystic Ovary Syndrome-related breakout and the usual aftermath, dark spots and all. Admittedly, after one week of using the serum, I didn’t observe any evident changes to my skin – apart from it feeling bouncier and more hydrated – but by week three, I noticed the pigmentation and dark spots that followed my breakout appeared to have faded.
For context, my post-acne dark spots usually take at least six weeks to start fading on their own, and other vitamin C serums have only ever managed to brighten them in a month. Using the brand’s crystal retinal alongside the C-Tetra advanced serum in the morning, the inflammation had calmed down a lot. My skin’s texture appeared a lot smoother, and my breakouts healed almost entirely.
I also observed a steady improvement in my moisture barrier and the skin’s sensitivity. Even without having skincare on, my skin no longer felt tight immediately after using a cleanser. Towards the end of the testing period (week five), my skin felt visibly plumper and, more importantly, healthier.
Buy now £69.00, Medik8.com
The verdict
The Medik8 C-Tetra advanced is one of the cleverest vitamin C serums I’ve tested. Although it comes with a hefty price tag, this stable and potent formula will fade hyperpigmentation, boost radiance, and reduce the appearance of the first signs of ageing. I haven’t stopped praising it ever since it first touched my face. Despite my sensitive, rosacea-prone skin, it didn’t result in any flare-ups, but it did help me manage my post-breakout inflammation while reinforcing my skin barrier.
Want more recommendations? Read our review of the best eye creams for mature skin
