If you love skincare, then the chances are you’ve already heard about Medik8. Known for its clinical, no-fluff and results-driven approach to skincare, this British-born brand is a favourite amongst dermatologists and beauty editors alike. At the heart of its bestselling CSA philosophy (vitamin C and SPF by day, vitamin A (AKA, retinol) by night—three ingredients clinically proven to improve your skin) is its cult-favourite C-Tetra serum range. These vitamin C serums are some of the most highly-regarded by skincare experts and you'll often spot them in the best skincare clinics, too.
But with three C-Tetra options now on the market—the OG Medik8 C-Tetra (£42), the luxurious C-Tetra Luxe (£59), and the newly launched C-Tetra Advanced (£69)—which one is actually right for you? I’ve spent the past few months trialling and testing each serum to find out. Here’s how they stack up.
Medik8 C-Tetra Serum Review
1. Medik8 C-Tetra Advanced
Medik8
C-Tetra® Advanced
Best for: Experienced vitamin C users, combination/oily skin, those wanting glow without an oily texture, for fading pigmentation, plumping wrinkles and smoothing uneven skin texture
Vitamin C strength: 20%
Ingredients: 20% stabilised vitamin C (tetrahexyldecyl ascorbate), phyto exosomes, acetyl zingerone, hyaluronic acid, N-acetyl glucosamine (NAG)
Texture: Lightweight, gel-serum
The latest release in the C-Tetra range, the C-Tetra Advanced promises a 20% vitamin C potency in a much lighter formula. The silky, quick-absorbing texture is ideal for those who find the original C-Tetra or C-Tetra Luxe too rich in texture, but still want a high-performing formula.
I’ve only had this in rotation for a few weeks since its launch, but the results are already so impressive. It's unlocked a serious glow in my skin, helping to fade post-acne marks and sun damage. It’s light enough to layer under SPF and moisturiser, doesn’t pill and gives a noticeable radiance even just after a week. And even on my reactive skin, I haven’t experienced any sensitivity so far. It may be down to the fact that Medik8 has included plant exosomes, which work in tandem to support the skin barrier and minimise skin irritation. As someone with oily skin, I appreciate the silky texture that doesn't disturb my makeup or leave me looking shiny come 1pm.
Pros
- Highest strength of vitamin C at 20%
- Brightens pigmentation and scarring, plumps wrinkles and smoothes skin texture
- Defends against environmental damage
- Absorbs quickly and layers beautifully under SPF and makeup
- Ideal for all skin types, but particularly combination and oily skin
Cons
- If you're very sensitive to vitamin C, it may be too strong
- The most expensive formula out of the three versions
2. Medik8 C-Tetra Luxe
Best for: Dry or mature skin, or anyone chasing a glass-skin glow
Vitamin C strength: 14%
Ingredients: 14% stabilised vitamin C (tetrahexyldecyl ascorbate), squalane, vitamin E, maracuja oil, red ginseng
Texture: Rich oil-serum
With the second-highest concentration of vitamin C, the C-Tetra Luxe takes everything the original does well and dials it up: double the vitamin C, added squalane and maracuja oil for a more nourishing formula.
The texture is richer—definitely more of an oil-serum texture—but it melts beautifully into dry skin, leaving a dewy, luminous finish. My skin looked smoother, brighter, and more even-toned after a month. Those with oily or combination skin may find the formula too nourishing, but for dry or mature skin, this will offer all the nourishment your skin is craving.
Pros
- Potent 14% vitamin C concentration
- Rich, nourishing oils leave skin glowing
- Great for dry, dull or mature skin
- Luxurious feel and finish
Cons
- May feel too heavy for oily or acne-prone skin
- Higher price point compared to the original C-Tetra serum
3. Medik8 C-Tetra
Medik8
Vitamin C Tetra Serum
Best for: Vitamin C beginners, sensitive skin
Vitamin C strength: 7%
Ingredients: 7% stabilised vitamin C (tetrahexyldecyl ascorbate), vitamin E
Texture: Lightweight serum
The original C-Tetra serum is the gentlest in the line-up at 7%. The texture is light with a slight oil texture, but is fast-absorbing and non-greasy once it sinks in. On my combination skin, it felt silky but didn’t leave me greasy. I noticed a subtle brightening of my skin tone and a softening of pigmentation around my cheeks. If you’re just getting started with vitamin C, C-Tetra is an excellent place to begin. It’s simple, gentle, and actually delivers a glow over time. The addition of vitamin E makes it nourishing and skin-softening too.
Pros
- Gentle and non-irritating
- Absorbs quickly with no sticky residue
- Subtle, consistent results over time
- Ideal for vitamin C newbies or sensitive skin
Cons
- Can feel slightly oily on oilier skin types
- Those who are used to a stronger vitamin C may benefit from opting for the C-Tetra Advanced or C-Tetra Luxe instead
The Verdict
Medik8’s C-Tetra line offers one of the most accessible, stable and elegant vitamin C ranges on the market. Whether you're a beginner or a glow obsessive, there’s a serum in this trio that will suit your skin. I can see why Medik8's formulas are so trusted amongst experts. The formulas are rigorously tested and optimised to deliver results, so you know if you invest in one of these three serums, you're going to see visible benefits.
Having tested the new C-Tetra Advanced for the past couple of weeks, I can visibly see how much clearer and glowing my skin is. In fact, it's clinically proven to brighten skin and improve the look of wrinkles in just a week. I'd recommend this one if you want a potent vitamin C serum, or prefer a gel-serum texture that sinks in quickly.
The C-Tetra Luxe and original C-Tetra are also brilliant. Having tested them both before, it really comes down to your preferences on texture and formula. The former has a 14% vitamin C concentration and comes in a richer, oil-serum consistency. I'd recommend this one for mature skin or those with dry skin types that crave a more nourishing formula on their skin.
As for the C-Tetra, the 7% vitamin C formula is ideal for those who are new to using vitamin C. The texture is more akin to a traditional serum that sinks in quickly, so it will suit most skin types.
Shop More Medik8:
Medik8
Crystal Retinal 3 Serum
Vitamin A (AKA, retinol) is a core part of Medik8's CSA philosophy. The brand's hero Crystal Retinal uses retinaldehyde, a more potent form of retinol that delivers better results over time, helping to plump wrinkles, even the skin tone and brighten pigmentation. There are varying strengths of this serum, so you can move up in strength as your skin adjusts.
Medik8
Advanced Day Ultimate Protect SPF 50+
Combined with vitamin A and vitamin C, SPF joins the ranks of these three ingredients that are proven to deliver results. This SPF 50+ is like insurance for your skin, helping to shield it against damage and maintain the benefits you see from your skincare routine.
Medik8
Liquid Peptides Advanced MP
Medik8's Liquid Peptides Advanced MP not only helps to plump the skin and boost collagen production, but contains growth factor mini proteins which helps to relax dynamic expression lines on the skin. It can even help to prolong the results of Botox.
Medik8
Crystal Retinal Ceramide Eye 3
The best-selling Crystal Retinal formula also comes in an eye cream, which is ideal for targetting wrinkles and dark circles.
Medik8
Advanced Night Restore
The Advanced Night Restore cream is perfect for pairing with your vitamin A treatments to help minimise irritation.
Why Trust Us
At Who What Wear UK, we know that beauty isn’t one-size-fits-all. Our editors have tested thousands of products, including skincare, makeup, hair and nails, over the years and work closely with trusted experts—dermatologists, make-up artists and leading industry insiders—to ensure every guide is well-researched, inclusive and relevant to you.
We focus on formulas that deliver, whether they’re affordable favourites or luxury investments. Our product selection is based on tangible results, ingredient know-how and what we’d truly recommend to a friend.
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