Option A
C E Ferulic
SkinCeuticals · £169
A morning L-ascorbic acid step under sunscreen
Head to head · Skin prep
SkinCeuticals C E Ferulic vs Medik8 C-Tetra.
The most-studied form of vitamin C at a premium price, against a stable, water-free derivative at a quarter of the cost.
Option B
C-Tetra
Medik8 · £45
A water-free morning vitamin C step
The verdict
Should I buy SkinCeuticals C E Ferulic or Medik8 C-Tetra?
Choose SkinCeuticals C E Ferulic if you want the most-studied form of vitamin C — 15% L-ascorbic acid with vitamin E and ferulic acid, fragrance-free — and accept £169. Choose Medik8 C-Tetra at £45 for a stable, water-free oil with 7% tetrahexyldecyl ascorbate. Both go on in the morning, under sunscreen.
Desk research, not a wear test. Prices are UK guide prices from official pages or named retailers when checked, and may have changed. How we compared.
Side by side
The specifications, compared.
Every row is drawn from the official product page or a named UK retailer listing. Brand wear and performance figures are the brands’ own.
| Specification | SkinCeuticals C E Ferulic | Medik8 C-Tetra |
|---|---|---|
| Brand | SkinCeuticals | Medik8 |
| Format | Antioxidant serum | Vitamin C oil serum |
| Finish | Light, silky | Lightweight oil |
| Vitamin C form | L-ascorbic acid, 15% | Tetrahexyldecyl ascorbate, 7% |
| Other antioxidants | Vitamin E 1%, ferulic acid 0.5% | Vitamin E |
| Base | Water-based serum | Water-free lightweight oil |
| Size and price | 30ml, £169 | 30ml, £45 (8ml travel size £15) |
| Fragrance | Listed as fragrance-free by Space NK | Grapefruit peel oil; limonene, citral, linalool and geraniol listed |
| Directions | Four to five drops each morning on dry skin, then moisturiser and SPF | Four drops each morning, then sunscreen; patch test first |
| Stability | L-ascorbic acid oxidises and can darken over time | Derivative designed to resist oxidation |
| Where to buy in the UK | Authorised retailers such as LOOKFANTASTIC, Cult Beauty and Space NK | Medik8’s UK store and UK retailers |
| Guide price | £169 | £45 |
Checked 25 September 2026. Prices, shade ranges and formulas can change; the official page is the final word.
Which to choose
Choose by what you need.
Choose C E Ferulic if…
- You want L-ascorbic acid, the form with the deepest research base
- You want stated percentages for three antioxidants
- You prefer a fragrance-free formula
- Price is not the deciding factor
Choose C-Tetra if…
- You want a vitamin C serum under £50
- L-ascorbic acid serums have felt uncomfortable on your skin
- You like a water-free oil texture
- You want to try a travel size first
What they have in common
- Both are morning antioxidant steps, used under sunscreen
- Both include vitamin E
- Both come in 30ml bottles with a dropper or pipette
- Neither replaces sunscreen
How we compared
Desk research, stated plainly.
This comparison is desk research. We lined up the two products’ published formulas, ingredient lists, sizes, directions and UK prices from official pages or named UK retailers on 25 September 2026. Neither product was tested in a laboratory or worn by our editors for this page.
There is no overall score. Two well-made products can suit different skin, budgets and routines, so the verdict is framed as “choose this if”. Brand claims are reported as brand claims, and no brand paid to be compared.
Questions
C E Ferulic vs C-Tetra, answered
Is L-ascorbic acid better than tetrahexyldecyl ascorbate?
- L-ascorbic acid has far more published research. Tetrahexyldecyl ascorbate is more stable in the bottle, but there is less evidence on how much becomes active vitamin C in skin. “Better” depends on whether you prioritise evidence or stability and comfort.
Why is C E Ferulic so much more expensive?
- SkinCeuticals prices it at £169 for 30ml at UK retailers. The formula combines three stated antioxidants; price alone is not evidence that one serum outperforms another.
Does Medik8 C-Tetra contain fragrance?
- Medik8 says there is no artificial fragrance, but grapefruit peel oil and fragrance allergens such as limonene and citral appear in the ingredient list.
Has SkinCeuticals C E Ferulic been reformulated?
- A reformulated US version was announced in July 2026. UK retailer ingredient lists checked on 25 September 2026 still showed the established formula, so check the pack you buy.
Sources
Where the facts come from.
- SkinCeuticals C E Ferulic, official product page (opens in a new tab)
- Medik8 C-Tetra, official product page (opens in a new tab)
- LOOKFANTASTIC — SkinCeuticals C E Ferulic 30ml (opens in a new tab)
- Space NK — SkinCeuticals C E Ferulic (opens in a new tab)
- Pullar JM, Carr AC, Vissers MCM (2017) — The Roles of Vitamin C in Skin Health, Nutrients (opens in a new tab)
- Telang PS (2013) — Vitamin C in dermatology, Indian Dermatology Online Journal (opens in a new tab)
All sources checked . Spotted an error? Email desk@thecastindex.com or read our corrections policy.
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