What We Tested…
Medik8’s C-Tetra Advanced Gel-Serum ($72)
Why Reyna Tested...


Test Results...
Texture. This serum is super lightweight and airy, plus it smells great. I used a few pumps at a time, and applied the cream to both my face and neck. The texture is creamy, but not watery. I let the product dry once it’s been applied, and I could hardly tell I’ve even put anything on. My face simply shined.
Sensitive-Skin-Friendly. This serum has a high percentage of vitamin C (20% Tetrahexyldecyl Ascorbate to be exact) coupled with Phyto Exosomes, a plant-derived extract that’s full of proteins, lipids, and messenger molecules to help soothe and support your skin barrier. Even with my extra sensitive skin, I noticed these soothing Phyto Exosomes protecting me from irritation.
Blendability. I applied moisturizer after this serum and the product blended in perfectly. I’m finding that throughout the day my face is looking brighter from wearing this product (with or without makeup).
Why Blake Tested...


Test Results...
Fresh smell and texture. I loved this formula right off the bat. This vitamin C gel-serum almost feels like a light moisturizing cream with the scent of fresh citrus — it’s like my skin is on summer vacation. The serum went on smoothly and there was no pilling when I layered it with my SPF, which is huge for me.
Brightening effect. The major change I noticed was in my skin’s brightness levels. This stuff really works. I noticed a difference after only a few days. When it’s dry out, my skin can appear a bit dull, but after using this serum, my skin looked and felt refreshed.
Why Lizzy Tested...


Test Results...
Layerability. I immediately loved how light this gel-serum felt on my skin. It absorbed quickly without any stickiness and layered easily under my moisturizer. It’s exactly what I want in my summer skincare – something that plays well with a full face of makeup and doesn’t slide off midday.
Glow effect. Did someone say glazed doughnut? Right away, my skin looked healthy, moisturized, and radiant — like I’d actually gotten eight hours of sleep (spoiler: I didn’t).
Antioxidants. Vitamin C serums help shield the skin from environmental damage (like pollution from living in a big city), which can accelerate signs of aging. Enter: acetyl zingerone, a super antioxidant that helps boost the benefits of vitamin C to defend against environmental stressors. If only it worked on subway delays.
Sidenotes...
Suitable for all skin types. This non-greasy C-Tetra Advanced Gel-Serum is formulated for all skin types, especially those with oily and combination skin. Our sensitive skin testers™ report having no breakouts or dryness after use.
Phyto Exosymes-packed formula. This serum uses tea leaf-extracted phyto exosomes to help support the skin barrier — delivering anti-inflammatory bioactives throughout skin cells. This formula combines high-strength vitamin C with these barrier-soothing phyto exosomes, leaving you with brighter, smoother-looking skin, sans irritation.
The Fine Details...
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