What safety data exist for GHK-Cu, separated by route: topical trials, skin-cell irritation tests, and the FDA concern about injectable GHK-Cu.
By the GHK-Cu Peptide editorial team · Last reviewed · Editorial review: pending
Short answer
The side-effect profile of GHK-Cu in people is not established for any route. The human data are three small randomised topical trials and uncontrolled multi-ingredient studies; keratinocyte tests found no irritation signal at the concentrations tested [Li 2016]. For injectable use, FDA cites immunogenicity risk from aggregation and impurities, and limited human safety data [FDA 2026].
By route of exposure
Applied to skin
Three randomised topical trials are indexed (86, a number not given in the abstract, and 13 participants) [Bishop 1992][Mulder 1994][Miller 2006]. Their abstracts focus on efficacy outcomes; the 1994 trial also reported fewer ulcer infections with the gel [Mulder 1994].
In a keratinocyte model, GHK-Cu was not cytotoxic and did not significantly change the irritation markers measured, while copper chloride and copper acetate behaved differently at the same concentrations [Li 2016].
A placebo-controlled hair study of a copper-free GHK complex reported no adverse events in any group of 45 men [Lee 2016].
Microneedle pre-treatment increases how much peptide and copper cross the skin; its safety was assessed in cell and pig models, not in people [Li 2015].
Injected into the skin
One uncontrolled study gave intradermal scalp injections of a formulation with six or more actives, including copper tripeptide-1, to 1,000 people [Kapoor 2018]. Any adverse event cannot be attributed to a single ingredient. Its companion cell and animal study assessed the full formulation [Kapoor 2020].
Other injectable and systemic routes
No human study of GHK-Cu given by injection into the body or through the nose is indexed.
FDA lists “GHK-Cu (for injectable routes of administration)” in Category 2 of bulk substances that may present significant safety risks in compounding [FDA 2026].
In rats, intravenously given copper-free GHK was rapidly broken down to His-Lys and eliminated [Endo 1997]. A 2026 mouse preprint found that intraperitoneal and intranasal dosing produced different gene-expression programmes in the brain [Mazzola 2026], a reminder that route changes what is measured.
A 2026 review of peptides sold directly to the public, including GHK-Cu, reports that rigorous human safety data for these unapproved peptides are scarce [Mendias 2026].
Product quality as a safety question
GHK-Cu degrades by hydrolysis under basic and oxidative stress, and its degradation products include free histidine [Badenhorst 2016]. Different materials sold as “GHK-Cu” can differ in copper ratio and counter-ion, and a 2026 review stresses that formulation-dependent speciation and labile copper are rarely reported [Mateescu 2026]. Purity, identity and copper content are separate measurements; see laboratory testing. A 2026 critical review also notes that the published evidence does not establish safety of degraded formulations [Yi 2026].
What would answer the question
A randomised, vehicle-controlled, quadruple-masked phase 2 trial of a topical GHK-Cu gel was registered in 2026 and was recruiting at our last check [NCT07437586]. It concerns topical use only. GHK-Cu is not an approved drug [openFDA], and nothing on this site is guidance on using it. Regulatory detail: regulatory status.
Frequently asked questions
Is GHK-Cu safe?
Safety has not been established for any route in a dedicated human safety study. Small topical trials and keratinocyte tests have not reported specific problems, which is not the same as being shown safe. FDA has flagged injectable GHK-Cu as a compounding safety risk.
What side effects has GHK-Cu caused?
No pattern of side effects is described in the indexed abstracts, but most did not report adverse-event data in detail, and the human studies are small or uncontrolled. Absence of reports in small studies cannot rule out uncommon effects.
Why is FDA concerned about injectable GHK-Cu?
FDA cites the potential for aggregation and peptide-related impurities that may cause immune reactions (immunogenicity), and says there are limited human data to inform safety.
References
Li H, Toh PZ, Tan JY et al. (2016). Selected Biomarkers Revealed Potential Skin Toxicity Caused by Certain Copper Compounds. Sci Rep. PubMed 27892491 · doi:10.1038/srep37664[In vitro, grade D]
Li H, Low YS, Chong HP et al. (2015). Microneedle-Mediated Delivery of Copper Peptide Through Skin. Pharm Res. PubMed 25690343 · doi:10.1007/s11095-015-1652-z[Ex vivo, grade D]
Lee WJ, Sim HB, Jang YH et al. (2016). Efficacy of a Complex of 5-Aminolevulinic Acid and Glycyl-Histidyl-Lysine Peptide on Hair Growth. Ann Dermatol. PubMed 27489425 · doi:10.5021/ad.2016.28.4.438[Human, grade B]
Kapoor R, Shome D (2018). Intradermal injections of a hair growth factor formulation for enhancement of human hair regrowth - safety and efficacy evaluation in a first-in-man pilot clinical study. J Cosmet Laser Ther. PubMed 29482481 · doi:10.1080/14764172.2018.1439965[Human, grade B]
Mulder GD, Patt LM, Sanders L et al. (1994). Enhanced healing of ulcers in patients with diabetes by topical treatment with glycyl-l-histidyl-l-lysine copper. Wound Repair Regen. PubMed 17147644 · doi:10.1046/j.1524-475X.1994.20406.x[Human, grade A]
Bishop JB, Phillips LG, Mustoe TA et al. (1992). A prospective randomized evaluator-blinded trial of two potential wound healing agents for the treatment of venous stasis ulcers. J Vasc Surg. PubMed 1495150 · doi:10.1067/mva.1992.37086[Human, grade A]
Miller TR, Wagner JD, Baack BR et al. (2006). Effects of topical copper tripeptide complex on CO2 laser-resurfaced skin. Arch Facial Plast Surg. PubMed 16847171 · doi:10.1001/archfaci.8.4.252[Human, grade A]
Endo T, Miyagi M, Ujiie A (1997). Simultaneous determination of glycyl-L-histidyl-L-lysine and its metabolite, L-histidyl-L-lysine, in rat plasma by high-performance liquid chromatography with post-column derivatization. J Chromatogr B Biomed Sci Appl. PubMed 9187381 · doi:10.1016/s0378-4347(96)00460-4[Chemistry, grade D]
Mazzola J, Rosenfeld M, Tucker M et al. (2026). Middle-aged mice treated with GHK-Cu peptide administered intraperitoneally or intranasally show behavioral rescue but divergent hippocampal aging programs. Res Sq. PubMed 42245779 · doi:10.21203/rs.3.rs-9520102/v1[Animal, grade C]
Mendias CL, Awan TM (2026). Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Med. PubMed 41966639 · doi:10.1007/s40279-026-02437-0[Review, grade R]
Mateescu DM, Gavrilescu DM, Mincioaga RI et al. (2026). GHK-Cu as a Bioactive Metallopeptide and Drug-Delivery Cargo: Coordination Chemistry, Formulation Science, Therapeutic Evidence, and a Translational Roadmap. Pharmaceutics. PubMed 42797253 · doi:10.3390/pharmaceutics18091077[Review, grade R]
Yi KH, Kim HS, Lee HE et al. (2026). Peptides in Aesthetic Dermatology: Classification, Fibroblast-Centered Mechanisms, Delivery Technologies, and Clinical Evidence. Life (Basel). PubMed 42942246 · doi:10.3390/life16101660[Review, grade R]
Badenhorst T, Svirskis D, Wu Z (2016). Physicochemical characterization of native glycyl-l-histidyl-l-lysine tripeptide for wound healing and anti-aging: a preformulation study for dermal delivery. Pharm Dev Technol. PubMed 25384620 · doi:10.3109/10837450.2014.979944[Chemistry, grade D]
U.S. Food and Drug Administration (2026-04-22). Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Source[retrieved 2026-11-11]
U.S. Food and Drug Administration, openFDA. openFDA Drugs@FDA and NDC directory queries for prezatide, copper tripeptide and GHK. Source[retrieved 2026-11-11]
ClinicalTrials.gov (2026-02-02). Topical GHK-Cu Gel for Acute Skin Wound Healing (NCT07437586). Source[retrieved 2026-11-11]