GHK-Cu
Copper peptide, Glycyl-L-histidyl-L-lysine copper(II)
Copper-binding tripeptide with forty years of topical research behind it - and essentially none behind the injectable form people are buying.
Preclinical only
Widely sold as a topical cosmetic ingredient, which is a legal and well-established use. The injectable form is not approved and appears on the FDA's Category 2 bulk substances list.
What it is
GHK is a naturally occurring tripeptide - glycine, histidine, lysine - that binds copper(II) with high affinity. Plasma levels decline substantially with age, which is the origin of most of the anti-ageing framing around it. The copper complex is the active form and gives solutions their characteristic deep blue colour.
The split that matters
This is the one compound on this site where the route determines the evidence tier, and the distinction is routinely collapsed in marketing:
| Topical | Injectable | |
|---|---|---|
| Human trial evidence | Multiple randomised trials on skin quality, wound healing and hair | No published human randomised trial for any cosmetic, hair, or wound endpoint |
| Regulatory status | Established cosmetic ingredient, sold openly | FDA Category 2 bulk substance |
| Where the peptide acts | Directly on the tissue you are targeting | Systemically, then wherever it distributes |
The topical literature is genuinely decent: fibroblast collagen synthesis, improvements in skin density and fine lines, hair follicle effects, and wound healing in controlled settings. Forty years of published work.
The injectable literature, for cosmetic purposes, is close to empty.
If the goal is skin, topical is the better-supported option and also the safer one. Subcutaneous injection of a copper chelator to improve your face is a substitution of an unstudied route for a studied one - and the studied one puts the peptide directly where you want it.
Mechanism
GHK-Cu modulates a strikingly large number of genes - reported in the thousands - shifting expression toward repair. Concretely: it stimulates collagen, elastin and glycosaminoglycan synthesis in fibroblasts, supports angiogenesis, acts as a copper delivery vehicle for copper-dependent enzymes such as lysyl oxidase, and has antioxidant and anti-inflammatory effects. Copper is a required cofactor for the cross-linking that gives collagen its tensile strength, which is why the copper is not incidental packaging.
Practical notes
- Topical formulation quality varies wildly. Concentration, pH and vehicle determine whether anything penetrates. The blue colour tells you copper is present, not that the product works.
- Do not layer with direct vitamin C or strong acids in the same application. Low pH and copper chelation interact unfavourably; alternate morning and evening instead.
- Copper is cumulative. It is an essential trace mineral with a genuine upper limit. Sustained daily systemic dosing at multi-milligram levels is not the same risk profile as a serum on your face.
- A copper peptide will not fix sun damage, sleep debt, or a bad diet, and skin that is already excellent has very little headroom for any topical to demonstrate an effect.
Side effects and warning signs
Commonly reported
- Injection-site redness, stinging and transient blue discolouration
- Topically: irritation, especially when layered with vitamin C or strong exfoliating acids
- Theoretical copper accumulation with high-dose sustained systemic use
Stop and get medical help
- Signs of copper excess with prolonged high-dose injection: nausea, abdominal pain, unexplained fatigue
- Anyone with Wilson's disease or a copper metabolism disorder should not use systemic copper peptides at all
- Spreading injection-site redness or warmth
Sources
From the community
Discussion for this compound concentrates in r/Peptidesource and r/Biohackers.
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