Home / Evidence ledger / GHK-Cu
3 amino acids · copper-bound tripeptide
Mixed statusTwo genuinely different products share this name. The topical cosmetic version is legal, widely available, and has the strongest evidence of any cosmetic peptide. The injectable version is a separate regulatory question and is not settled.
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Schematic structure, not to scale. Beads represent amino acid residues along the backbone.
In theory, GHK-Cu is designed to restore a signal your body loses with age. Plasma levels fall by roughly two-thirds between twenty and sixty, by carrying copper into cells where it acts as an enzyme cofactor. Applied topically it is meant to protect the collagen you have and organise the collagen you make. Unusually for this list, the theory has largely held: gene expression work and controlled split-face trials both support it.
The detail, if you want it
GHK is a naturally occurring human tripeptide, glycine, histidine, lysine, found in plasma, saliva and urine. Levels decline substantially with age. GHK-Cu is that tripeptide bound to copper(II). Unlike most compounds on this site, it is not a laboratory invention. It is something your body already makes less of over time.
Legal as a cosmetic ingredient, sold over the counter, no prescription required. This is the best-evidenced peptide in cosmetic dermatology. Gene expression work has documented effects across a very large number of human genes, including upregulation of tissue inhibitors of metalloproteinases, which protect existing collagen, and decorin, which organises collagen fibrils. Clinical studies show improvements in skin density, thickness and elasticity in photoaged skin.
Most over-the-counter serums contain GHK-Cu at roughly 0.001–0.01%. The studies showing measurable collagen changes used concentrations one to three orders of magnitude higher. Buying a copper peptide serum is not equivalent to the research protocol, and the ingredient list rarely discloses the concentration. Position on the label is the only crude signal available.
A different regulatory track entirely, and not resolved. GHK-Cu for injection was placed in Category 2 in 2023. Following the April 2026 reclassification it is the one substance in that cohort that moved toward Category 1 rather than sitting in limbo, and non-injectable routes are under separate evaluation scheduled before the end of February 2027. Human outcome data for injected GHK-Cu is far weaker than for the topical form.
Do not layer topical GHK-Cu with direct ascorbic acid in the same application. Ascorbic acid reduces copper(II) to copper(I), which can generate free radicals and inactivate the peptide. Use them at different times of day.
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