Medik8 sells Liquid Peptides on one headline number: "10 powerful peptides in a 30% blend". This page reads Medik8's own ingredient list, as served on its UK product page on 23 September 2026, in label order. It then sets that number against what the list shows. The list printed on a given bottle can differ by region, and Medik8 says so itself.
The list, in order
The serum has 33 ingredients. Here are the first sixteen, before any peptide appears:
| Position | Ingredient | Role |
|---|---|---|
| 1 | Aqua (Water) | base |
| 2–3 | Glycerin, Butylene Glycol | humectant, solvent |
| 4 | Inulin | humectant |
| 5 | Sodium Hyaluronate | hyaluronic acid |
| 6 | Panthenol | provitamin B5 |
| 7 | Alpha-Glucan Oligosaccharide | prebiotic sugar |
| 8 | Carnosine | a dipeptide (beta-alanyl-histidine) |
| 9–11 | Carbomer, Polysorbate 20, Caprylyl Glycol | thickener, solubiliser, conditioning |
| 12 | Phenoxyethanol | preservative, capped at 1% |
| 13–16 | Hydroxypropyl Cyclodextrin, Dunaliella Salina extract, Ethylhexylglycerin, Citric Acid | carrier, algae extract, preservative booster, pH |
The nine named peptides then run from position 17 to 31:
| Position | Peptide (INCI) | Trade identity | PubMed records under the INCI name, 2026-09-23 |
|---|---|---|---|
| 17 | Palmitoyl Tripeptide-5 | Syn-Coll | 4 |
| 19 | Acetyl Hexapeptide-8 | Argireline | see our argireline file |
| 20 | Tetrapeptide-21 | — | 3 |
| 21 | Pentapeptide-18 | Leuphasyl | 4 |
| 22 | Palmitoyl Tripeptide-1 | Matrixyl 3000, half one | 2 |
| 24 | Palmitoyl Tripeptide-38 | Matrixyl synthe'6 | 3 |
| 25 | Palmitoyl Tetrapeptide-7 | Matrixyl 3000, half two | see our Matrixyl file |
| 30 | Copper Palmitoyl Heptapeptide-14 | the "drone-targeted copper peptide" | 0: phrase not found |
| 31 | Heptapeptide-15 Palmitate | its partner | 0: phrase not found |
Positions were counted by hand and checked against a second, separate reading of the list. No name on it contains a comma, so a simple split did not shift anything.
Where the 30% sits
On an ingredient list in descending order, the preservative is a landmark. EU and UK cosmetics rules cap phenoxyethanol at 1% when it is used as a preservative. It sits at position 12, so everything below it is present at 1% or less. All nine named peptides are below it. That is an inference from the order of the list, not a figure Medik8 discloses. It is also the most a label lets a reader say about content.
It is not in conflict with "a 30% blend". Peptide trade ingredients reach formulators as dilute solutions: a small amount of peptide carried in water, glycerin or butylene glycol. A formula can hold 30% of those solutions and still hold little peptide by weight, and those carriers also appear on this list as glycerin and butylene glycol at positions 2 and 3. The 30% measures the solutions put in, not the peptide in the bottle. How to read an ingredient order more generally is set out in our guide to reading a peptide ingredient list, and The Ordinary's Multi-Peptide + HA Serum is another multi-peptide formula read the same way.
Between positions 13 and 33 the order is not alphabetical, so the list gives no clean signal of where the 1% block begins. The phenoxyethanol line is the only one the label supports.
Ten peptides: which ten
The nine INCI names above make nine, and the description says ten. The likeliest tenth is carnosine at position 8, a two-amino-acid peptide (beta-alanine plus histidine), sold here as an antioxidant. It is the only peptide above the preservative line. It is also the only one whose name does not say "peptide", so a reader counting names on the label arrives at nine.
What each peptide's file holds
The Matrixyl trio (positions 22, 24, 25) has the most published work of anything on this list. Even so, the evidence is thin: two records under palmitoyl tripeptide-1 and three under palmitoyl tripeptide-38 by INCI name, with most of the Matrixyl 3000 work filed under its trade name and sequence. Our Matrixyl file counts it under every name.
The expression-line pair, acetyl hexapeptide-8 (Argireline) and pentapeptide-18 (Leuphasyl), is the combination sold as a topical answer to muscle-driven lines. Pentapeptide-18 is an enkephalin analogue from opioid research, and its record is set out in our pentapeptide-18 file. No human trial of it on its own was found.
Palmitoyl tripeptide-5 and tetrapeptide-21 have four and three PubMed records respectively under those names. Both are collagen-signalling claims, and neither has a trial that isolates it in a finished serum.
The copper pair is where the list and the literature part ways. PubMed reported both INCI phrases as not found on 23 September 2026. A careless search misses that: when PubMed cannot match a quoted phrase, it quietly matches the words separately. Here that returned 187 and 40,706 unrelated "hits". The actual count under these names is zero. The copper peptide with a human literature is GHK-Cu (copper tripeptide-1), covered in our copper peptides guide, and it is not on this list.
The brand's study, as published
The product page makes three "7 days" claims: firmness and plumpness, fine lines and wrinkles, and younger-looking skin. Beside them it reports "98% agree Liquid Peptides is gentle on the skin" and "97% experienced long-lasting hydration". All of these carry one footnote: "Proven via independent consumer study on Liquid Peptides on 60 participants over 8 weeks." The product description calls the 7-day result "clinically proven".
A consumer study records what participants report. The page names no instrument measurement, no untreated side or control group, no published paper, and no breakdown of the 60 by age or skin type. So the 7-day figures are self-assessments on a whole formula of 33 ingredients, 5 of them humectants or hyaluronic acid. They cannot be traced to any one peptide.
What the label settles, and what it leaves open
It settles that the serum lists nine peptide INCI names, all below the 1% preservative line, and that carnosine is the likeliest tenth. It settles that the "30%" describes a blend of ingredient solutions. And it shows that two of the nine have no PubMed record under their label names.
It leaves open how much of each peptide is in the bottle, which the label does not give. It also leaves open whether the formula changes skin in ways an instrument would measure. A consumer study does not answer that, and neither does this page. For the category as a whole, see what a peptide serum can and cannot do.
Sources
- Medik8, Liquid Peptides product page (UK), medik8.com/products/liquid-peptides: ingredient list, "10 powerful peptides in a 30% blend", the "Proven Results" block and its footnote, 30 ml at £59. Fetched with plain
curland read 2026-09-23; the page title confirmed the product. - Regulation (EC) No 1223/2009 on cosmetic products, Annex V (preservatives), entry for phenoxyethanol, maximum 1% in ready-for-use preparation. EUR-Lex. The UK retained the same limit.
- PubMed E-utilities searches, 2026-09-23, per INCI name as quoted phrases, with the
quotedphrasesnotfoundfield read for each: palmitoyl tripeptide-5 (4), tetrapeptide-21 (3), pentapeptide-18 (4), palmitoyl tripeptide-1 (2), palmitoyl tripeptide-38 (3), copper palmitoyl heptapeptide-14 and heptapeptide-15 palmitate (phrase not found). - U.S. FDA, 21 CFR 701.3, ingredient labeling of cosmetics in descending order of predominance. eCFR.