The answer, first. GHK-Cu has the deeper literature of the two, and that literature is worse than its reputation: three randomised trials in forty years, two of them negative. AHK-Cu is thinner still — a handful of cell and small cosmetic studies. Neither has a measurement of elastin in a living human. This is a comparison between a thin record and a thinner one.
Side by side
The same two axes this site applies to every compound, with nothing added for the comparison.
| GHK-Cu | AHK-Cu | |
|---|---|---|
| Clinical evidence | 3 RCTs, 2 negative | cosmetic only |
| Community adoption | very high | niche |
| Category | skin | skin |
| Our summary | Copper tripeptide with a deep preclinical literature on skin remodeling and wound healing, and almost no human efficacy data. The only randomised trial on facial skin with blinded objective endpoints was null. We grade it route by route in a dedicated report. | A copper-binding tripeptide marketed mainly for hair growth. The published evidence amounts to a handful of cell and small cosmetic studies — far thinner than the literature behind its cousin GHK-Cu. |
| Full file | GHK-Cu → | AHK-Cu → |
What actually separates them
Three differences that hold up against the published record, rather than against marketing.
What neither can tell you
- What is in the vial. A comparison between molecules says nothing about the contents of a specific lot. Only a certificate of analysis does, and most cover fewer measures than buyers assume — start with how to read a COA.
- A dose. This site describes what published protocols used and never prescribes.
- Which is right for you. That is a clinical question about an individual, and nothing here is medical advice.
Questions we get
Is GHK-Cu or AHK-Cu better for skin?
GHK-Cu has the deeper published literature of the two, but deeper is not the same as good: it amounts to three randomised trials in forty years, two of which were negative. AHK-Cu is thinner again, with a handful of cell and small cosmetic studies, and it is marketed mainly for hair rather than skin. Neither has a measurement of elastin in a living human.
Do injectable copper peptides work better than topical?
No published randomised human trial with a skin endpoint supports any injectable research peptide for skin, copper peptides included. Our collagen and pore report ranks forty interventions against the actual human trial record, and the interventions that hold multi-year randomised evidence are not peptides.
Why is GHK-Cu so popular then?
Adoption and evidence are graded separately on this site. GHK-Cu carries very high community adoption alongside a clinical grade that reflects three RCTs, two of them negative. The divergence between those two facts is the point of grading them on separate axes.