I'm a beauty editor and this is the best vitamin C serum I've ever used (2025)

Applying vitamin C serum every morning can feel like flossing: I know it's good for me but I'd often rather skip it. The Medik8 C-Tetra Advanced serum changed all that.

As a beauty editor, I've probably road-tested upwards of 200 different vit-C serums in my career. They all beat a familiar drum – ‘great for skin-brightening!’, ‘the ultimate protection against environmental damage!’– but only a handful have turned into repeat purchases.

So why, if vitamin C remains one of the most Googled skincare ingredients on the planet, am I so picky when it comes to using it? The texture of many vitamin C serums is my biggest bugbear – and I'm a big believer that you have to enjoy using a beauty product in order to remain loyal to it.

Vitamin C is rightfully code for glow but a lot of the serums laced with this ingredient actually have heavy, oily formulas that give me breakouts and make me look sweaty. Others feel too watery, meaning I have to use a separate hyaluronic acid serum and moisturiser to pump hydration into my skin.

So it's been hard to find a Goldilocks, just right formula – until now. Within seconds of applying the C-Tetra Advanced's milky-thin, gel-serum formula – a rarity among vitamin C serums – a switch was thrown. Now here was a product I could get behind…

C-Tetra® Advanced

Medik8 C-Tetra Advanced: The science bit

When people find out what I do for a living, the first question they inevitably ask me is, “What skincare ingredients should I be using?”. The answer is always the same as I swear by the magic three – vitamin C, retinol and hyaluronic acid – all ingredients that dermatologists incidentally wax lyrical about, too.

You can already find two of these ingredients in the Medik8 C-Tetra Advanced, which is powered by 20% stabilised vitamin C for brightening and hyaluronic acid for hydration. But there are two other superstar ingredients in the formula that deserve a special mention.

The first is plant exosomes. You may recognise these as there's been a lot of buzz in the cosmetic tweakments space about this ingredient. Exosomes are essentially lipids that are extracted from plants, which have been found to encourage cell-to-cell communication, helping to repair damaged skin and reduce inflammation.

In the Medik8 C-Tetra Advanced serum, the plant exosomes are from green tea. They encapsulate the vitamin C, carrying it deeper into the skin, while also having a soothing effect and protecting the skin barrier. So even sensitive skin or first time vitamin C users can avoid irritation from a high dose of vitamin C.

The other ingredient of note is acetyl zingerone. It doesn't exactly trip off the tongue but this is what skincare formulators call a ‘super antioxidant’. What that means is it boosts the power of vitamin C – another potent antioxidant – to give your skin even more protection against damage from pollution and UV rays.

C-Tetra® Advanced

Medik8 C-Tetra Advanced: My verdict

The clinical claims around the Medik8 C-Tetra Advanced are pretty impressive: it visibly brightens the skin in 7 days; it reduces pollution damage to the skin's surface by 90% and there is 0% barrier disruption despite this being a high potency 20% vitamin C serum. So how does the science stack up to the user experience?

I'm a beauty editor and this is the best vitamin C serum I've ever used (2025)
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