A bottle of Medik8 C-Tetra Lipid Vitamin C Radiance Serum open with its dropper resting diagonally across the top. Set against a clean white background, the bottle is surrounded by three clear puddles of serum, showcasing its liquid texture.
Close-up portrait of a woman with her eyes closed, showcasing a bright and even skin tone. Text highlights that the product "Restores the look of skin radiance in 7 days," delivers a visibly brighter tone, and increases skin youthfulness.
Close-up of a woman with a glowing, radiant complexion resting her hand on her cheek. Text states: "87% of sensitive skins agree this is the most gentle vitamin C serum they have ever used." Smaller text below notes results based on a consumer study.
"MEET YOUR VITAMIN C" chart on an orange gradient background with hexagonal graphics. Four Medik8 serums are shown. From left: C-Tetra dropper bottle (7% Vitamin C, for sensitive skins or beginners), C-Tetra Luxe dropper bottle (14% Vitamin C, for dry skin), C-Tetra Advanced pump bottle (20% Vitamin C, for normal, combination, and oily skin), and Super C Ferulic dropper bottle (30% Ethylated L-Ascorbic Acid, for experienced users).
An infographic titled "HOW TO LAYER" displaying a four-step morning routine: Cleanse (Surface Radiance Cleanse), Tone (Press & Glow), Vitamin C (C-Tetra), and Sunscreen (Advanced Day Total Protect). Expert advice at the bottom suggests pairing with vitamin A at night.
A comparison table titled "FIND YOUR VITAMIN C" featuring six Medik8 products. It lists each product name, its Vitamin C percentage, and its ideal user—ranging from C-Tetra Cream (3% Vitamin C) for beginners to Super C Ferulic (30% Ethylated L-Ascorbic Acid) for experienced users.
An infographic titled "THE CSA PHILOSOPHY" explains a three-step skincare approach: Vitamin C in the morning to brighten, Sunscreen in the morning to protect, and Vitamin A at night to renew. The text claims this addresses 90% of anti-ageing skincare needs.
An amber glass bottle of Medik8 C-Tetra lipid vitamin C radiance serum shown next to its white cardboard carton. Both are set against a clean white background with a subtle shadow.
A travel-sized 8mL amber glass bottle of Medik8 C-Tetra lipid vitamin C radiance serum standing next to its white cardboard carton. The products are displayed on a textured grey surface against a clean white background.
A bottle of Medik8 C-Tetra Lipid Vitamin C Radiance Serum open with its dropper resting diagonally across the top. Set against a clean white background, the bottle is surrounded by three clear puddles of serum, showcasing its liquid texture.
Close-up portrait of a woman with her eyes closed, showcasing a bright and even skin tone. Text highlights that the product "Restores the look of skin radiance in 7 days," delivers a visibly brighter tone, and increases skin youthfulness.
Close-up of a woman with a glowing, radiant complexion resting her hand on her cheek. Text states: "87% of sensitive skins agree this is the most gentle vitamin C serum they have ever used." Smaller text below notes results based on a consumer study.
"MEET YOUR VITAMIN C" chart on an orange gradient background with hexagonal graphics. Four Medik8 serums are shown. From left: C-Tetra dropper bottle (7% Vitamin C, for sensitive skins or beginners), C-Tetra Luxe dropper bottle (14% Vitamin C, for dry skin), C-Tetra Advanced pump bottle (20% Vitamin C, for normal, combination, and oily skin), and Super C Ferulic dropper bottle (30% Ethylated L-Ascorbic Acid, for experienced users).
An infographic titled "HOW TO LAYER" displaying a four-step morning routine: Cleanse (Surface Radiance Cleanse), Tone (Press & Glow), Vitamin C (C-Tetra), and Sunscreen (Advanced Day Total Protect). Expert advice at the bottom suggests pairing with vitamin A at night.
A comparison table titled "FIND YOUR VITAMIN C" featuring six Medik8 products. It lists each product name, its Vitamin C percentage, and its ideal user—ranging from C-Tetra Cream (3% Vitamin C) for beginners to Super C Ferulic (30% Ethylated L-Ascorbic Acid) for experienced users.
An infographic titled "THE CSA PHILOSOPHY" explains a three-step skincare approach: Vitamin C in the morning to brighten, Sunscreen in the morning to protect, and Vitamin A at night to renew. The text claims this addresses 90% of anti-ageing skincare needs.
An amber glass bottle of Medik8 C-Tetra lipid vitamin C radiance serum shown next to its white cardboard carton. Both are set against a clean white background with a subtle shadow.
A travel-sized 8mL amber glass bottle of Medik8 C-Tetra lipid vitamin C radiance serum standing next to its white cardboard carton. The products are displayed on a textured grey surface against a clean white background.
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C-Tetra®

  • Brighten
  • |
  • Even
  • |
  • Smooth
Lipid 7% Vitamin C Radiance Serum
Restore the look of skin radiance in just 7 days* with cult-favourite C-Tetra. 

Formulated with a stabilised form of vitamin C (7%) called tetrahexyldecyl ascorbate (pronounced 'tetra-hexul-deckul as-CORR-bate'), this lightweight serum works to visibly brighten uneven skin tone and reduce the look of fine lines and wrinkles, while remaining gentle on sensitive skin.

Fortified with vitamin E, this antioxidant powerhouse also protects the skin against the ageing and damaging effects of free radicals for a more youthful and healthy-looking complexion overall. The perfect option for those who are new to vitamin C, or those with sensitive skin.
Select a Size
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Reasons to shop Medik8

Free UK delivery over £25
15% off your first order
"No questions asked" easy 30 day returns
Advanced Day Ultimate Protect™
Advanced Day Ultimate Protect™
  • Protect
  • |
  • Repair
  • |
  • Hydrate
 Age-Defying Moisturiser with Photolyase SPF 50+ | PA++++
Full Size (50ml)
View our verified proof
Sustainability

Provenance provides confidence for sustainability claims; helping to prevent 'green-washing' and empowering conscious consumers to purchase in line with their values. Provenance 'Proof Points' are all third party verified and evidenced through supply chains.

Product proof points

The Vegan Trademark

C-Tetra is Vegan Society certified — free from animal ingredients. No animals used in the product's manufacturing or testing. Free from GMOs. Reviewed by the Vegan Society.

Partly Recyclable Packaging

Recyclable Parts: Bottle (glass) and Container (cardboard) Non-Recyclable Parts: Pipette

Brand proof points

B Corporation

Medik8 is a certified B Corporation, scoring over 80 out of 200 across Governance, Workers, Community, Environment and Customers. The certification includes a legal commitment to consider all stakeholders in decision-making. Verified every three years.

SBTi Approved Targets

Medik8 has SBTi approved science-based targets to reduce greenhouse gas emissions in line with limiting global warming to 1.5°C or well-below 2°C. Progress is reported publicly every year, with targets validated by the certifier and reviewed every 5 years.

Living Wage Employer

Medik8 is a Living Wage Employer — all staff are paid a wage calculated to meet the cost of living in the UK. Company wages are updated annually after new rates are announced by the Living Wage Foundation.

Carbon Measured

The footprint was calculated using GHG Protocol methodology; GWP 100.

Renewable Energy

Medik8's Innovation Centre uses electricity from 100% renewable sources.

Made in Britain

Medik8 carries the Made in Britain trademark — manufactured in the United Kingdom. Subject to facility verification and annual renewal.

Donates to Charity

In 2022 Medik8 donated £10,000 to the National Society for the Prevention of Cruelty to Children

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Key Benefits
Increased Skin Youthfulness

Proven to simultaneously smooth the look of fine lines and wrinkles while visibly boosting skin glow and radiance.

Lightweight Nourishment

This jojoba (pronounced 'huh-hoh-ba') seed oil-based formula delivers effective yet non-greasy nourishment for visibly softer and comforted skin.

Brighter, More Even Complexion

Proven to visibly brighten the skin tone, for a more even and healthy-looking skin appearance.

Proven Results
7 days to restored skin radiance*
7 days to visibly brighter smoother skin*
96% of sensitive skins agreed C-Tetra was gentle on the skin*
4 weeks to visibly reduced wrinkles & dark spots*
90% agree skin feels instantly softer*
*Proven via independent consumer study conducted over 4 weeks on 52 participants with sensitive skin. | Please Note: Product packaging shown may be different to the product received due to regional variations.
How to Use

First-time use

If you're new to C-Tetra, we recommend a patch test at least 24 hours before first use. Learn how to patch test here.


Step 1

After cleansing in the morning, massage 4 drops across the face, neck and décolletage.


Step 2

Leave to absorb before applying sunscreen. We recommend Advanced Day Ultimate Protect.

Uses per bottle

200
Guide to Layering
Step 1: Cleanse
Medik8 Surface Radiance Cleanse tube displayed on a clean white background with a large, translucent gel texture smear. Text identifies it as a Resurfacing AHA/BHA Mangosteen Cleansing Gel in a 150mL size.
Morning
Evening
Surface Radiance Cleanse™
Select a Size
Step 2: Tone
Medik8 Press & Clear bottle (150ml) displayed on a white background with splashes of blue tonic around it. Text highlights the
Morning
Evening
Press & Clear™
Select a Size
Step 3: Brighten
A bottle of Medik8 C-Tetra Lipid Vitamin C Radiance Serum open with its dropper resting diagonally across the top. Set against a clean white background, the bottle is surrounded by three clear puddles of serum, showcasing its liquid texture.
Morning
C-Tetra®
Select a Size
Step 4: Sunscreen
Advanced Day Ultimate Protect™
Morning
Advanced Day Ultimate Protect™
Full Size (50ml)
Key Ingredients
7% Stabilised Vitamin C (tetrahexyldecyl ascorbate)

A low-irritation form of vitamin C that delivers exceptional antioxidant protection against harmful free radical damage while brightening and supporting collagen production for a visibly even, more youthful-looking complexion.

Vitamin E

A powerful antioxidant that provides additional antioxidant protection against the ageing effects of free radicals. It also helps to boost the power of vitamin C for optimum visible results.

Full List of Ingredients
C-Tetra®
Lipid 7% Vitamin C Radiance Serum

Simmondsia Chinensis (Jojoba) Seed Oil, Cyclopentasiloxane, Cyclohexasiloxane, Tetrahexyldecyl Ascorbate, Citrus Grandis (Grapefruit) Peel Oil, Tocopheryl Acetate, PPG-12/SMDI Copolymer, Limonene, Citral, Linalool, Geraniol.

*Although we try our best to ensure this list of ingredients is accurate there may be product upgrades from time to time, or slight variants between different regions based on local laws, meaning the only definitive ingredient list is that which is printed on the product packaging.
  • No artificial fragrance
  • No synthetic colours
  • Paraben free
  • Certified by the vegan society
Expert Recommended

"Ultra-gentle & perfect for visibly radiant skin."

DANIEL ISAACS
Chief Product Officer

"I like everything that Medik8 does and this is no exception."

EVE CAMERON
Beauty Director - Red

The Vitamin C Serum Range

A bottle of Medik8 C-Tetra Lipid Vitamin C Radiance Serum open with its dropper resting diagonally across the top. Set against a clean white background, the bottle is surrounded by three clear puddles of serum, showcasing its liquid texture.
Morning
C-Tetra®
Full Size (30ml) | £45
Strength

7% Stabilised Vitamin C

Texture

Lightweight oil

Skin Types

New to Vitamin C, Sensitive skin

Benefits
  • Brightens
  • Ultra gentle
Key Ingredients
  • 7% Tetrahexyldecyl Ascorbate
  • Vitamin E
Medik8 C-Tetra Luxe serum bottle shown open with its glass pipette resting against the rim, displayed on a white background with clear, translucent serum droplets. The image includes a "GET THE GLOSS BEAUTY AWARDS GOLD 2024" seal in the top left and a "DERMATOLOGIST RECOMMENDED" emblem with a magnifying glass icon in the top right.
Morning
C-Tetra® Luxe
Full Size (30ml) | £62
Strength

14% Stabilised Vitamin C

Texture

Rich oil

Skin Types

All skin types, First signs of ageing

Benefits
  • Brightens
  • Nourishes
  • Softens Look Of Wrinkles
Key Ingredients
  • 14% Tetrahexyldecyl Ascorbate
  • Squalane
  • Maracuja Oil
Medik8 C-Tetra Advanced bottle displayed on a clean white background with translucent serum droplets, highlighting its lightweight gel-serum texture.
Morning
C-Tetra® Advanced
Full Size (30ml) | £72
Strength

20% Stabilised Vitamin C

Texture

Lightweight Gel-Serum

Skin Types

All skin types, Visible signs of ageing

Benefits
  • Brightens
  • Defends Against Premature Skin Ageing
  • Smooths Skin Texture
  • Visibly  Improves Wrinkles
  • Advanced Pollution Protection
  • 0% Barrier Disruption
Key Ingredients
  • Phyto Exosomes 
  • 20% Tetrahexyldecyl Ascorbate
  • Acetyl Zingerone
Medik8 Super C Ferulic serum bottle shown open with its glass pipette resting against the rim, displayed on a clean white background with translucent serum droplets. The amber glass bottle features the Medik8 logo and is labeled "SUPER C FERULIC Potent Vitamin C Brightening Serum" in a 30mL size.
Morning
Super C Ferulic™
Full Size (30ml) | £69
Strength

30% Stabilised Vitamin C

Texture

Rich, oil like serum

Skin Types

Advanced signs of sun induced ageing

Benefits
  • Brightens
  • Intense Dark Spot Reduction
  • Visibly Reduces Wrinkles
Key Ingredients
  • 30% Ethylated L-Ascorbic Acid
  • Ferulic Acid
  • Vitamin E
  • Turmeric Root Extract

Complete Your Regime

Reviews

Frequently Asked Questions

Is C-Tetra suitable for sensitive skin?

Yes, C-Tetra was designed with gentleness in mind. It has been formulated using a very gentle form of vitamin C called THDA (tetrahexyldecyl ascorbate) that is suitable for all skin types, even if you’re new to vitamin C. C-Tetra has also been tested on an independent consumer panel of sensitive skins, of which 93% agreed it is gentle on their skin.[3]

Do I have to use C-Tetra before I can try any of Medik8’s stronger vitamin C serums?

No, you do not have to use C-Tetra before trying our other vitamin C products. Our vitamin C products have been created to provide options for different strengths and textures to suit all preferences, so you can choose the one that best fits your needs. If you have sensitive skin and would prefer to try a lower-strength vitamin C, C-Tetra is the right one for you.

Does C-Tetra Advanced contain fragrance/essential oils?

C-Tetra does not contain synthetic fragrance. It features a subtle, naturally derived citrus aroma from a very low concentration of essential oils, designed to leave the sensorial experience without compromising skin comfort.

Why do you use essential oils/fragrance in your day products - are they safe?

To create a beautiful product which we know our customers will want to use every day, we use "low-fragrance" in some products as experience is absolutely key to Medik8. For example, we sometimes use a low level of essential oils to imbue a formula with a subtle and elegant aroma. The fragrances themselves are at low levels and with reduced allergens; at these tiny percentages they are extremely unlikely to irritate the skin.

If you have any specific concerns about sensitivities, we always recommend doing a patch test before applying the serum to your face or more sensitive areas. This simple step can help ensure the product is right for you.
C-Tetra®
Full Size (30ml)
Select a Size