iS Clinical GeneXC Serum Review
The Verdict
GeneXC Serum is the highest-percentage, most recently launched vitamin C serum in iS Clinical's range — a reasonable choice if you already use vitamin C and want to move up in concentration without the fridge-storage commitment Super Serum Advance+ asks for. It isn't the place to start if you're new to active serums, and the natural colour-darkening that comes with pure L-Ascorbic Acid is worth expecting rather than being surprised by. Read the full Super Serum Advance+ comparison if you're torn between the two, and speak to our team before use if you're pregnant or breastfeeding.
iS Clinical GeneXC Serum | Vitamin C Serum | 15ml & 30ml
£169.00
GeneXC Serum is iS Clinical's newest vitamin C serum, built around 20% time-released L-Ascorbic Acid alongside the brand's proprietary Extremozyme® blend — Kakadu plum (Terminalia Ferdinandiana), plankton extract and arginine ferulate. It's positioned as the range's most technologically dense vitamin C formula, one of four vitamin C options iS Clinical sells through Skintique alongside Super Serum Advance+, Pro-Heal Serum Advance+ and Poly-Vitamin Serum. It's a twice-daily serum rather than an occasional treatment, so it's worth being clear how it differs from its closest sibling, Super Serum Advance+, before choosing between them — covered below.
What it is
GeneXC Serum is a lightweight, silky-textured serum that iS Clinical says absorbs quickly without residue. The formula centres on 20% L-Ascorbic Acid using a time-released delivery system, intended to reduce the irritation typically associated with high-percentage vitamin C while maintaining potency. Alongside it sits the Extremozyme® blend, marketed as the brand's most advanced antioxidant technology, drawing on ingredients from land and sea. iS Clinical describes the formula as helping to support the skin's environmental defences and even out the appearance of tone; we haven't repeated the brand's gene-activation or DNA-protection language here, since that's a marketing claim rather than something we can independently verify. Pure L-Ascorbic Acid also oxidises naturally over time, so GeneXC Serum can darken in the bottle — expected with high-percentage vitamin C, and stated not to affect performance.
| Key active | 20% L-Ascorbic Acid (time-released) |
|---|---|
| Extremozyme® blend | Kakadu plum (Terminalia Ferdinandiana), plankton extract, arginine ferulate |
| Size | 15ml / 30ml |
| Texture | Lightweight, silky, fast-absorbing |
| Skin types | All, including sensitive, mature and photoaged skin (per product listing) |
| AM/PM | Both — listing states suitable for twice-daily use |
| Colour | May naturally darken over time — normal, doesn't affect performance |
| Pregnancy | Not stated on the product listing either way — see below |
Key ingredients
- L-Ascorbic Acid (20%, time-released) — the antioxidant vitamin C form, helping support the skin's defences against environmental stress and even out the appearance of tone.
- Kakadu plum (Terminalia Ferdinandiana) — a botanical extract in the Extremozyme® blend, included for its own antioxidant content.
- Plankton extract — a marine-derived antioxidant, the "sea" half of the land-and-sea Extremozyme® positioning.
- Arginine ferulate — an antioxidant compound in the same blend, related to ferulic-acid derivatives generally associated with stabilising vitamin C formulas.
Who it's for
GeneXC Serum suits people who already use a vitamin C serum and want the newest, most concentrated formula in iS Clinical's range, comfortable with twice-daily active-serum use. The listing states it's suitable for sensitive and photoaged skin too, though we'd still suggest patch testing any new active first. It's less suited to anyone put off by natural colour-darkening, or wanting a fridge-stable option — Super Serum Advance+ has more explicit storage guidance in that direction, below.
How it compares to Super Serum Advance+
GeneXC Serum and Super Serum Advance+ are the two vitamin C serums most likely to get confused, since both sit at the top of the range and centre on high-percentage L-Ascorbic Acid. Super Serum Advance+ pairs 15% time-release vitamin C with bioidentical Copper Tripeptide-1 and recommends refrigeration. GeneXC Serum uses a higher 20% concentration alongside the Extremozyme® blend instead of the copper peptide. See our full Super Serum Advance+ vs GeneXC Serum comparison for the complete breakdown.
If you'd rather have a fragrance-free vitamin C serum that also contains retinol, Pro-Heal Serum Advance+ is the more comparable option — built differently again, and carrying the range's clearest brand-stated pregnancy caution.
How to use it
iS Clinical positions GeneXC Serum for morning and evening use, on clean skin before heavier moisturisers. Patch test on the inner forearm first and introduce it once daily before moving to twice-daily use if your skin tolerates it well. A broad-spectrum SPF is still essential every morning — vitamin C supports the skin's environmental defences, it doesn't replace sun protection.
GeneXC Serum also appears in our Best iS Clinical Serums for Anti-Ageing guide, alongside the range's other treatment serums sorted by mechanism.
Pregnancy and breastfeeding
The product listing doesn't carry any pregnancy or breastfeeding guidance either way for GeneXC Serum, so we haven't inferred one. If you're pregnant or breastfeeding, please contact our team for advice before use.
FAQs
What is Extremozyme® technology?
iS Clinical's name for a blend of antioxidant ingredients from land and sea — in GeneXC Serum, that's Kakadu plum, plankton extract and arginine ferulate, alongside the serum's 20% L-Ascorbic Acid.
Is iS Clinical GeneXC Serum the same as Super Serum Advance+?
No. Super Serum Advance+ pairs 15% vitamin C with Copper Tripeptide-1 and needs refrigeration, while GeneXC Serum uses 20% vitamin C with the Extremozyme® blend instead. See our full comparison for the details.
Why has my GeneXC Serum changed colour?
Natural darkening is expected with high-percentage L-Ascorbic Acid as the vitamin C oxidises, and iS Clinical states it doesn't affect performance. If texture or smell change too, contact us rather than assuming it's the same process.
Can I use it morning and evening?
iS Clinical positions it for twice-daily use. If you're new to vitamin C serums, we'd suggest starting once daily and building up as your skin tolerates it.
Does GeneXC Serum need to go in the fridge?
No fridge storage is stated on the listing, unlike Super Serum Advance+, which iS Clinical recommends refrigerating.
Is it safe to use during pregnancy?
The listing doesn't state a pregnancy caution either way. If you're pregnant or breastfeeding, please contact our team for advice before use.