AHK-Cu: what it is, what the one study found and what is unknown

AHK-Cu is a tripeptide made of alanine, histidine and lysine, bound to a copper(II) ion. It belongs to the small family of copper peptides used in cosmetics, of which the best known is GHK-Cu, glycyl-L-histidyl-L-lysine copper, a molecule first isolated from human serum in 1973 ^[3]. AHK differs from GHK by one amino acid at the first position: alanine instead of glycine. That single change means AHK-Cu is a synthetic design rather than a natural human peptide, and it also means that the large body of GHK research, which runs to decades of cell, animal and small human studies, does not automatically apply to it.

The name is written AHK-Cu, AHK Cu peptide, AHK copper peptide or copper tripeptide AHK; on ingredient lists the cosmetic name copper tripeptide-1 refers to GHK-Cu, not AHK-Cu, and the two are sometimes confused. A palmitoylated version, Pal-AHK, is also sold. Research peptide stores list AHK-Cu in lyophilised vials under headings such as cosmetic peptides or hair peptides, usually alongside GHK-Cu, Pal-GHK and PTD-DBM. For how that market works in general, see what research peptides are.

The reason a copper peptide is expected to affect hair goes back to the wider copper peptide literature. Reviews of topical anti-ageing peptides place copper peptides in a category of carrier peptides, meaning peptides whose main job is thought to be delivering a metal ion, copper, to enzymes in the skin that need it ^[6]. Whether AHK-Cu does anything that GHK-Cu does not, or anything that free copper does not, has never been tested directly.

There is one primary research paper on AHK-Cu. In 2007 a group at Seoul National University College of Medicine tested L-alanyl-L-histidyl-L-lysine-Cu2+ on human hair follicles kept alive in culture and on cultured dermal papilla cells, the specialised fibroblasts at the base of each follicle that control hair growth. At concentrations from 10⁻¹² to 10⁻⁹ M, AHK-Cu stimulated the elongation of the hair follicles and the proliferation of dermal papilla cells. At 10⁻⁹ M it also reduced the number of dermal papilla cells undergoing apoptosis, although that reduction was not statistically significant; the ratio of the survival protein Bcl-2 to the death protein Bax rose and the cleaved forms of caspase-3 and PARP fell. The authors proposed that AHK-Cu promotes hair follicle growth by stimulating dermal papilla cells to divide and by discouraging them from dying ^[1].

That is the whole of the direct mechanistic evidence. It is a plausible finding, since dermal papilla cell number and survival are closely linked to hair follicle size and the length of the growth phase, and it is consistent with what has been reported for GHK-Cu, which the same paper describes as a growth factor for various differentiated cells that stimulates fibroblast proliferation and raises VEGF production ^[1]. GHK-Cu stimulates collagen synthesis in fibroblast cultures at similar concentrations, beginning between 10⁻¹² and 10⁻¹¹ M and peaking at 10⁻⁹ M ^[2], so the two copper tripeptides appear to act in the same concentration range in cells.

The copper is probably important. Chemical studies of GHK show that it binds copper(II) very tightly, with a conditional dissociation constant in the region of 10⁻¹⁴ M at physiological pH, through its N-terminal amine, a backbone amide nitrogen and the histidine imidazole ring ^{[4] [5]}. AHK keeps the histidine at the second position and the lysine at the third, so it is expected to hold copper in the same way, though its binding constant has not been published. Bound this way, the copper is chemically inert under moderate redox conditions, which is thought to be what makes copper peptides tolerable to cells at concentrations where free copper would generate damaging radicals ^[4].

None of this tells us what happens on a scalp. The hair-growth field has moved towards the Wnt/β-catenin pathway as the master switch for follicle regrowth, a pathway that peptides such as PTD-DBM target directly ^[7]. AHK-Cu has not been tested against that pathway, and no study has looked at whether it reaches the follicle from a topical product.

The AHK-Cu benefits claimed by sellers are thicker and faster-growing hair, reduced hair loss, and, borrowing from GHK-Cu, skin repair and collagen production. Searches for AHK-Cu hair growth and AHK-Cu vs GHK-Cu are the two most common questions about it. The evidence for each claim is set out below.

Hair growth: the single 2007 study is positive but was entirely in vitro. Follicles elongated in culture and dermal papilla cells multiplied when exposed to AHK-Cu at nanomolar concentrations ^[1]. Hair follicle organ culture is a standard first screen for hair-growth candidates, and many compounds that lengthen follicles in a dish have gone on to fail in animals or people, so the result is a reason to study AHK-Cu further, not evidence that it grows hair on a human head. There is no animal study of AHK-Cu that we could find, and no human study of any kind. A 2025 review of hair-loss cosmeceuticals lists peptides among the ingredient classes in use and notes that effectiveness and safety substantiation remain the field’s main challenges ^[8]; AHK-Cu is a good example of an ingredient whose use runs ahead of its data.

Skin and collagen: no study has tested AHK-Cu on skin, wounds or collagen. Sellers extend the GHK-Cu literature to AHK-Cu on the basis that the two share the His-Lys copper-binding motif. A 2025 review of topically applied GHK found that even for GHK-Cu, the far better-studied peptide, there is a surprising absence of clinical studies of the commercial forms used in anti-wrinkle products, despite good evidence in cells ^[9]. If the clinical record for GHK-Cu is thin, the record for AHK-Cu is blank.

AHK-Cu vs GHK-Cu: no head-to-head study exists in any system. Marketing claims that AHK-Cu is more potent for hair than GHK-Cu, or that it is the hair peptide while GHK-Cu is the skin peptide, are not drawn from published comparisons. The one point of difference that can be stated is structural: GHK occurs naturally in human plasma, saliva and urine, with levels that fall with age, whereas AHK has never been reported in the body.

There are no human studies of AHK-Cu and no registered clinical trials as of September 2026. We searched PubMed for the peptide under its chemical and trade names and ClinicalTrials.gov for any registered study; the only research paper is the 2007 in vitro study ^[1]. Product pages that quote percentage improvements in hair density or hair count for AHK-Cu are drawing on unpublished ingredient-supplier data, which cannot be checked.

By comparison, the nearest clinical evidence for a copper peptide and hair comes from small trials of combination products containing GHK-Cu, discussed on the GHK-Cu page, and from a body of Wnt-pathway work in which the anti-epileptic drug valproic acid, not a peptide, increased hair counts in a 24-week randomised trial of 40 men with androgenetic alopecia ^[10]. Those results belong to other compounds and say nothing about AHK-Cu, but they show what a hair-growth claim looks like when it has been tested.

Because there are no human or animal studies, there is no answer. In the follicle culture study, elongation was measured over days in the laboratory ^[1]. On a scalp, any hair-growth product needs at least three to six months before a change in hair count could be measured, because the growth phase is long and new hairs take time to reach visible length; that is the timescale used in the valproic acid trial above ^[10]. Anyone trying AHK-Cu and seeing a difference within weeks is seeing something other than new follicle growth.

The only AHK-Cu dosage information in the literature is the concentration range used in cell and follicle culture: 10⁻¹² to 10⁻⁹ M, which is roughly 0.0004 to 0.4 nanograms per millilitre of culture medium ^[1]. That is a laboratory bath concentration and does not translate into a topical percentage or an injected dose. Cosmetic serums that list AHK-Cu typically contain it at fractions of a percent, a figure set by the ingredient supplier rather than by any dose-finding study.

No published study has given AHK-Cu by injection, by mouth or under the skin at any dose, so there is no injected dose to report and these figures are not recommendations. Research stores sell vials in amounts such as 50 mg or 100 mg, far larger than the quantities that would ever be applied to a scalp; the peptide calculator converts vial contents to a solution concentration for laboratory use, but there is no studied dose to calculate towards.

In cosmetics, AHK-Cu is used in scalp serums, leave-in treatments and occasionally facial products, and the evidence question is whether a tripeptide-copper complex applied to the scalp reaches the dermal papilla. Small peptides penetrate skin poorly; a 2014 study on excised human skin found that tripeptides, tetrapeptides and pentapeptides all stayed mainly in the upper layers unless microneedles were used, which increased delivery 2 to 22 fold ^[11]. The hair follicle itself is a route into the skin for topical products, and copper peptides are small, so some penetration to the follicle is plausible, but it has not been measured for AHK-Cu.

Research peptide suppliers sell AHK-Cu as a blue lyophilised powder in vials, the colour coming from the copper complex. Some buyers dissolve it into a home-made scalp solution, which at least matches the route the in vitro data suggest. Injecting AHK-Cu, whether into the scalp or under the skin, has never been studied in any species. Injectable copper peptides are also different from oral or topical ones in that the copper load goes straight into tissue; GHK-Cu, the analogue with the most data, has itself never been tested by injection in a published human trial, as the GHK-Cu guide explains.

AHK-Cu side effects have not been recorded in any study because there has been no study in people or animals. In cell culture the peptide was tested at concentrations up to 10⁻⁹ M without reported toxicity ^[1], which says nothing about the milligram quantities in a vial. The 2007 paper measured apoptosis markers precisely because copper compounds can be toxic to cells; the finding that AHK-Cu reduced rather than increased apoptosis markers is reassuring at nanomolar concentrations only.

The main theoretical concern with any copper peptide is copper itself. Copper bound to GHK is redox-inert under moderate conditions ^[4], but a poorly made or partly degraded product could carry free copper, and copper ions catalyse the formation of reactive oxygen species. Topical copper peptides have a long history of use without notable safety signals, which is some comfort for scalp use. For injection, there are no data at all, and a certificate of analysis showing the peptide content does not tell you how much copper is present or in what form.

A 2026 paper proposing a safety-evaluation framework for cosmetic peptides notes that the industry is replacing animal toxicity studies with bioinformatic screening for toxin and allergen similarity ^[12]. That is the level of safety substantiation a cosmetic ingredient like AHK-Cu receives: a screen against databases, not a clinical safety study.

AHK-Cu is not an approved medicine anywhere. It is used as a cosmetic ingredient in the UK, EU and US within the general rules for cosmetics, which require the company marketing a product to hold safety data but do not require proof that it works. It has not been the subject of any FDA compounding decision and is not on the WADA Prohibited List. Any claim that a product containing it treats hair loss, as opposed to improving the appearance of hair, would be a medicinal claim requiring a licence that no AHK-Cu product holds.

Sold as a research chemical in a vial, it falls under the general rules for research peptides. See our legal status overview, with country pages for the UK and the US.

Lyophilised AHK-Cu is stored cold, dry and away from light; see how to store peptides. In solution, the copper complex is more stable than the free peptide but the solution should still be refrigerated and used within a limited period. Bacteriostatic water is the usual laboratory solvent; for a topical solution, the peptide will be less stable than in a commercially formulated product with chelators and preservatives. A change from blue to green or brown suggests the copper has been released or oxidised.

AHK-Cu is a short peptide and cheap to make, but the copper complexation step adds a variable that ordinary peptide testing does not capture. Compare AHK-Cu prices across suppliers, and check listings in the UK and the US. Price per milligram is the only meaningful comparison in the absence of a studied dose; see peptide prices explained.

A certificate of analysis for AHK-Cu should report the peptide mass, about 354 g/mol for the free tripeptide, and an HPLC purity figure. Few COAs report the copper content, which is the number that distinguishes a copper peptide from a plain tripeptide, so ask for it or look for a supplier that publishes elemental analysis. Our guides to reading a COA, third-party testing and spotting a fake supplier explain what to look for, and our list of third-party tested suppliers shows which stores publish independent results. For the wider hair-growth field, see peptides for hair growth.