I Tried Skin Diligent’s Vitamin C Serum for a Month – Here’s My Honest Review

I’ll be honest—I have always rated using a vitamin C serum or facial oil as part of my skincare routine. Over the years I’ve tried everything from supermarket own-brand products costing under a tenner to premium luxury formulas promising miracle results. Some have been perfectly nice, others have been disappointingly sticky or greasy, and a few have simply done… well, nothing.

So when Skin Diligent sent me its Vitamin C Serum-in-Oil to try, I wasn’t expecting to be particularly surprised.

Fast forward a month, having used it every morning and evening, and I can genuinely say this is probably the best vitamin C product I’ve come across.

First Impressions

The first thing I noticed wasn’t actually my skin—it was the texture.

Most facial oils I’ve used in the past have left me looking shiny for half the day or feeling as though they’re sitting on top of my skin. This is completely different.

Despite being an oil-based serum, it absorbs remarkably quickly and feels far lighter than I expected. Within a minute or two my skin simply felt comfortable, hydrated and smooth rather than oily.

The fragrance deserves a mention too. It’s subtle, fresh and natural without being overpowering. It disappears quickly, which I personally prefer as I don’t want my skincare competing with my perfume.

The Results After Four Weeks

I’m always wary of skincare brands promising dramatic overnight transformations because, in my experience, good skincare simply doesn’t work like that.

What I did notice over the course of a month was a steady improvement.

The biggest change has been my complexion. My skin tone looks noticeably more even, and areas of mild redness have softened considerably. My skin also feels smoother to the touch, particularly across my cheeks where texture can sometimes be a little uneven.

It’s one of those products where people start saying, “Your skin looks really nice,” without necessarily knowing why.

That’s usually the best compliment a skincare product can receive.

More Than Just Vitamin C

One of the reasons this serum interested me was that it isn’t simply another vitamin C product.

Skin Diligent uses Ascorbyl Tetraisopalmitate, a stable oil-soluble form of vitamin C that’s designed to penetrate the skin more effectively while remaining gentle enough for regular use.

Alongside that, the formula contains an impressive blend of antioxidant-rich ingredients including cocoa extract, pomegranate, moringa, hemp seed oil and camelina oil, all selected to help support the skin barrier and protect against environmental stress.

While I can’t pretend to measure collagen production or oxidative stress in my bathroom mirror, I can say my skin has looked healthier, brighter and much more balanced since incorporating it into my routine.

It Layers Beautifully

Another pleasant surprise is how well it fits into an existing skincare routine.

I applied it after cleansing before moisturiser both morning and night, and it layered beautifully underneath SPF and makeup without causing pilling or leaving an oily finish.

That isn’t always the case with facial oils.

Is It Worth £62?

There’s no escaping the fact that £62 is an investment.

However, because only two or three drops are needed each time, the bottle lasts much longer than you might expect.

Having used countless vitamin C products over the years, I genuinely think this one justifies its price if you’re looking for something that delivers visible improvements while feeling luxurious to use.

My Verdict

There are very few skincare products that I finish and immediately know I’d buy again.

This is one of them.

It feels beautifully formulated, absorbs effortlessly, smells lovely without being overpowering and, most importantly, I’ve actually noticed a difference in my skin.

After four weeks my complexion appears brighter, the texture is smoother and my skin simply looks healthier.

I’ve tested plenty of vitamin C serums over the years, but Skin Diligent’s Vitamin C Serum-in-Oil has quietly become my favourite.

Rating: ★★★★★ (4.5/5)

Product provided for review. All opinions are my own and based on four weeks of independent testing.

Joanne Brook-Smith is a writer and editor with two decades of publishing experience. She launched Crave Magazine during the Covid period to create a fresh, inspiring space for food, travel and lifestyle content.