AHK-Cu vs GHK-Cu
Last updated: October 4, 2026 · 6 min read · By the Grey Peptides Editorial Board
- AHK-Cu and GHK-Cu differ by a single amino acid: alanine in place of glycine at the front of the chain.
- GHK-Cu occurs naturally in human blood and has a literature of cell, animal and a few small human studies.
- AHK-Cu has one published study: it lengthened human hair follicles kept alive in a dish. No human trial has tested it.
- Claims that AHK-Cu is the 'hair' copper peptide and GHK-Cu the 'skin' one rest on that single laboratory study, not on head-to-head data.
Side by side
AHK-Cu Low and GHK-Cu Medium are both copper complexes of three-amino-acid peptides 1. The table is read from our encyclopedia entries.
| Field | AHK-Cu | GHK-Cu |
|---|---|---|
| Encyclopedia entry | AHK-Cu Short entry | GHK-Cu Full entry |
| Molecule class | Peptide | Peptide |
| Category | Cosmetic | Healing & Recovery |
| FDA status | Research Chemical | Research Chemical |
| Approved elsewhere | None recorded | None recorded |
| Evidence grade | Low | Medium |
| Half-life | Undetermined | Undetermined (systemic) |
| Formula | C15H26CuN6O4 | C14H23CuN6O4 |
| Molecular weight | 417.9 g/mol | 402.9 g/mol |
| WADA 2026 | Prohibited (S0 catch-all) | Prohibited (S0 catch-all) |
| WADA 2027 | Prohibited (S0 catch-all) | Prohibited (S0 catch-all) |
| In one line | A tripeptide copper complex studied primarily for hair follicle stimulation and anagen induction in cosmetic applications. | A copper-binding tripeptide found in human plasma and sold widely in skin care; the evidence is mostly cell and animal work, with few trials in people. |
| Mechanism | In the one study that names it, AHK-Cu at picomolar to nanomolar concentrations lengthened human hair follicles kept alive outside the body and made dermal papilla cells divide faster, while shifting the Bcl-2/Bax balance away from apoptosis (Pyo et al., 2007). Copper is a cofactor for lysyl oxidase and several antioxidant enzymes; the peptide is proposed to carry it into cells, a proposal drawn from the GHK-Cu literature rather than tested for AHK-Cu. | GHK-Cu upregulates expression of genes involved in tissue remodeling, collagen and glycosaminoglycan synthesis, and antioxidant defense. It modulates the expression of decorin, integrins, and fibroblast growth factors, and has been shown in genomic studies to reverse multiple age-related gene expression changes. The copper cofactor is essential for lysyl oxidase activity in collagen cross-linking. |
| Sources in the entry | 2 | 18 |
| Study cards | None (short entry) | 14 |
| Dosage page | None | Dosage page |
One amino acid apart
GHK is glycyl-histidyl-lysine; AHK is alanyl-histidyl-lysine. Both bind a copper ion tightly through the histidine and the free amino end, which is why both are sold as copper complexes. The difference is the first amino acid: glycine, the smallest, versus alanine, which carries one extra methyl group. That change is small chemically, but enough that results for one cannot simply be assumed for the other.
GHK has an origin story AHK lacks. It occurs naturally in human plasma, and in one study people with COPD had lower plasma GHK than healthy controls (70 against 133 ng/mL), with lower levels tracking smaller muscles (human and animal study) 2. AHK is a synthetic analogue with no comparable natural role described in the literature we found.
What AHK-Cu has shown
The whole AHK-Cu literature naming it on PubMed is a single 2007 laboratory study. Researchers kept human hair follicles alive in culture and treated them with AHK-Cu at very low concentrations, 10-12 to 10-9 molar. The follicles grew longer, and dermal papilla cells, the specialised cells at the base of the follicle that drive hair growth, multiplied faster. At the highest concentration, markers of cell death shifted in a favourable direction, though the reduction in dying cells was not statistically significant (laboratory study) 3.
That is a promising laboratory signal and nothing more. Hair follicles in a dish are not hair on a scalp, the concentrations bear no known relation to what a topical product delivers to the follicle, and no study has applied AHK-Cu to people and measured hair counts.
What GHK-Cu has shown
GHK-Cu has a broader literature, though still thin in people. Its best-known effects are in wound healing in animals: in rats with implanted wound chambers, GHK-Cu increased collagen, DNA and protein in the healing tissue (animal study) 4, and in 72 rats after knee-ligament reconstruction, injections into the joint improved graft healing measures (animal study) 5. A 2018 review by GHK's leading researchers summarises effects on collagen, blood vessels, nerves and gene expression, much of it from cell and gene-expression data (review) 6.
The human trial evidence is small. In a randomised trial of skin care after laser resurfacing, 13 patients completed treatment, and computer analysis and blinded evaluators found no difference with GHK-Cu (randomised trial) 7. Our GHK-Cu entry covers the rest, and our GHK-Cu vs Matrixyl page compares it with a peptide that has a larger trial.
For hair: neither is proven
AHK-Cu is marketed as the copper peptide for hair, often in serums alongside GHK-Cu, caffeine and other actives. The only evidence specific to AHK-Cu is the follicle-culture study above (laboratory study) 3. GHK-Cu's hair evidence is also largely laboratory work. Our article on peptides for hair loss sets copper peptides beside minoxidil and finasteride, which have large placebo-controlled trials and regulatory approval for hair loss.
Multi-ingredient products make it impossible to tell which ingredient, if any, does anything; a serum with AHK-Cu and a dozen other actives tested as a whole says nothing about AHK-Cu itself.
For skin
GHK-Cu is the copper peptide with skin data, though the one small human trial we cite found no difference after laser resurfacing (randomised trial) 7. AHK-Cu has no skin study naming it. Products that pair the two for skin are relying on GHK-Cu's literature and on the assumption that a near-identical molecule behaves similarly, which has not been tested.
Injected copper peptides
Both are also sold online as injectable research peptides. That is a different product from a cosmetic serum. FDA's interim compounding categories have dealt with GHK-Cu for injectable routes specifically, as our category guide explains, and no study has tested injected AHK-Cu in people. Research-grade injectables carry the quality risks our marketplace article describes, and no dose has been established for either.
Status
Neither peptide is an approved drug. Both appear in cosmetic products, where they are not reviewed for effectiveness before sale, and both are sold as research chemicals 1. Our entries record each one's status with the date it was checked.
How they compare (as of October 4, 2026)
AHK-Cu and GHK-Cu are one amino acid apart. GHK-Cu occurs naturally in human blood and has a modest literature of cell, animal and a few small human studies, the best of which do not show clear benefit in people. AHK-Cu has a single laboratory study in which it lengthened human hair follicles in culture. For hair or skin, neither has the human trial evidence that approved treatments have, and the claim that one is better than the other for any purpose has no head-to-head study behind it.
Frequently asked questions
What is the difference between AHK-Cu and GHK-Cu?
One amino acid: AHK has alanine where GHK has glycine. Both are copper-binding tripeptides.
Is AHK-Cu better for hair than GHK-Cu?
There is no head-to-head study. AHK-Cu's only published study showed it lengthened human hair follicles in culture; neither has a human hair trial.
Does GHK-Cu occur naturally?
Yes. GHK is found in human blood plasma; AHK is a synthetic analogue.
Are copper peptides approved for hair loss?
No. Approved hair-loss treatments such as minoxidil and finasteride have placebo-controlled trials; copper peptides do not.
Related on Grey Peptides
Sources
- Grey Peptides dataset records for AHK-Cu (Ala-His-Lys copper complex, research-only, stub entry) and GHK-Cu (Gly-His-Lys copper complex, research-only, full entry); read October 4, 2026.
- Deng, M., et al. (2023). Glycyl-l-histidyl-l-lysine-Cu(2+) rescues cigarette smoking-induced skeletal muscle dysfunction via a sirtuin 1-dependent pathway. J Cachexia Sarcopenia Muscle, 14(3), 1365-1380. PMID: 36905132
- Pyo, H. K., et al. (2007). The effect of tripeptide-copper complex on human hair growth in vitro. Arch Pharm Res, 30(7), 834-9. PMID: 17703734
- Maquart, F. X., et al. (1993). In vivo stimulation of connective tissue accumulation by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+ in rat experimental wounds. J Clin Invest, 92(5), 2368-76. PMID: 8227353
- Fu, S. C., et al. (2015). Tripeptide-copper complex GHK-Cu (II) transiently improved healing outcome in a rat model of ACL reconstruction. J Orthop Res, 33(7), 1024-33. PMID: 25731775
- Pickart, L., et al. (2018). Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. Int J Mol Sci, 19(7). PMID: 29986520
- Miller, T. R., et al. (2006). Effects of topical copper tripeptide complex on CO2 laser-resurfaced skin. Arch Facial Plast Surg, 8(4), 252-9. PMID: 16847171
Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.
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