Skin, Hair & Immune

GHK-Cu / KLOW

Also known as GHK-Cu, GHK, Copper tripeptide-1, Copper peptide, Glycyl-L-histidyl-L-lysine, Glycyl-L-histidyl-L-lysine-Cu(II), Tripeptide-copper complex

A naturally occurring three-amino-acid peptide that carries copper into tissue, studied for decades in cell culture but tested in only a handful of small human trials.

How it works

Copper-binding peptides that signal the body to remove damaged collagen and replace it with healthy fibers.

Performance edge

Known for the "Glow" effect; essential for skin remodeling, hair regrowth, and reversing systemic inflammatory damage.

Plain-English guide

GHK-Cu / KLOW, without the jargon

What it is

GHK is a chain of just three amino acids - glycine, histidine and lysine - that occurs naturally in your own blood plasma, saliva and urine. It grips a copper ion tightly, and that pairing is what people mean when they write GHK-Cu, where Cu is the chemical symbol for copper. Blood levels of GHK are reported to average about 200 nanograms per millilitre at age twenty and around 80 nanograms per millilitre by age sixty, which is the observation that started the anti-ageing interest in it. It has been sold since the 1990s as a cosmetic ingredient called copper tripeptide-1, and almost everything published in humans tested it as a cream, a serum or an intradermal scalp injection rather than as the subcutaneous injection sold in research vials. KLOW is a separate multi-peptide blend that contains GHK-Cu alongside other peptides and has its own page; nothing below was tested as that blend.

What people use it for

Skin appearance - fine lines, firmness and texture, which is the use with the longest commercial history as a topical cosmetic ingredient
Recovery of skin after resurfacing procedures, which is what the one facial randomised trial actually measured
Chronic wounds and ulcers, the setting of the oldest controlled human trial
Hair density and shedding, where the human data come from a multi-ingredient scalp injection rather than GHK-Cu on its own
General anti-inflammatory and antioxidant claims, which so far rest on cell culture and gene-expression work rather than on people

How it works, simply

Think of the deeper layer of your skin as an old brick wall that has been patched badly for years. Copper is the mortar the repair crew needs, but loose copper is corrosive and cannot just be dumped on the wall. GHK works like a delivery pouch that holds a single copper ion and hands it over at the right place, while also telling the crew to knock out crumbling bricks before laying new ones. That is why the literature describes it as remodelling rather than simply building: it turns up both the making and the breaking down of collagen at the same time.

What to expect, and when

Before day 1There is no published human dosing timeline for injected GHK-Cu at all. Every timeline below comes from topical or intradermal studies, so treat any schedule you read for a research vial as convention rather than evidence.
Week 1-4In the 2006 carbon dioxide laser trial this was the erythema-resolution window, and blinded evaluators plus computer analysis found no difference between the GHK-Cu regimen and the control regimen.
Week 8-12Twelve weeks was the endpoint in that same trial. Everyone improved in wrinkles and skin quality after the laser, with no difference between groups on objective measures; only the patients' own questionnaire scores favoured GHK-Cu.
Month 6The 2018 open-label scalp study gave eight intradermal sessions three weeks apart, with reduced hair fall on the hair pull test in 83 percent of patients. That formulation contained five growth factors and thymosin beta-4 as well as copper tripeptide-1, so the peptide cannot be credited on its own.
Month 12+The only twelve-month human follow-up located is from that same uncontrolled scalp study, which reported a continued statistically significant increase in total hair count. Nothing longer or better controlled has been published.

Side effects and interactions

No treatment-related adverse events were attributed to the copper tripeptide arms in either controlled human trial located, which is not the same as none existing - both were small and neither was designed primarily as a safety study
In the 1992 venous ulcer trial the copper tripeptide cream performed no better than the inert vehicle placebo, so there was nothing to trade off against harm
The United States Food and Drug Administration has stated that compounded injectable drugs containing GHK-Cu may pose a risk for immunogenicity because of the potential for aggregation and peptide-related impurities, and that there are limited data in humans to inform safety considerations
Copper is a metal with a narrow useful range in the body, and no published human study has tracked serum copper, ceruloplasmin or zinc status during repeated injected use
Product quality is a real and separate hazard, because research-grade vials are not made under the controls that apply to a cosmetic or a medicine

Who should avoid it

You are pregnant, trying to conceive, or breastfeeding, as no reproductive safety data exist for GHK-Cu by any route
You have Wilson disease, a copper metabolism disorder, or any condition where copper handling is abnormal, since the whole point of the molecule is to deliver copper
You have a current or past cancer diagnosis, because the peptide is described throughout the literature as pro-angiogenic and as a driver of cell proliferation
You are taking copper chelating medicines such as penicillamine or trientine, where adding a copper carrier works against the treatment
You are not working with a physician who knows what you are taking and can check your bloodwork, including copper and zinc

Common mistakes

Assuming the topical research transfers to an injection. The human trials used creams, serums and intradermal scalp injections, and the FDA's stated concern about GHK-Cu is specifically about injectable routes
Reading the gene-expression headlines as clinical results. The claim that GHK can modulate around four thousand human genes comes from cell and database work, not from an outcome measured in a person
Treating the blue colour as a purity check. GHK-Cu solutions are blue because of the copper, and colour tells you nothing about peptide content, copper-to-peptide ratio or impurities
Storing it carelessly. Reconstituted peptide belongs refrigerated and shielded from light, and this one is also reported in the formulation literature to be unstable and awkward to keep in solution
Stacking it with other copper sources or high-dose zinc without measuring anything, since copper and zinc compete for absorption and neither is harmless at the extremes

Deep research

What the literature actually shows

Mechanism

GHK is a naturally occurring tripeptide - glycine, L-histidine, L-lysine - found in human plasma, saliva and urine. The 2020 review in Aging Pathobiology and Therapeutics reports plasma levels averaging about 200 ng/ml at age twenty and about 80 ng/ml by age sixty, and it is the copper(II) complex, GHK-Cu, that carries the biological activity attributed to it. The molecule is therefore usually described less as a drug than as a copper transport and delivery system that becomes scarcer with age.

Its best-characterised action is on the extracellular matrix. The 2015 review in BioMed Research International describes GHK stimulating both the synthesis and the breakdown of collagen and glycosaminoglycans, modulating the activity of matrix metalloproteinases and their tissue inhibitors, and specifically raising dermatan sulfate, chondroitin sulfate and the small proteoglycan decorin. It also restores replicative vitality to fibroblasts after radiation therapy and attracts immune and endothelial cells to an injury site. The 2026 systematic review in Aesthetic Surgery Journal reaches the same preclinical summary: across eighteen preclinical studies, GHK-Cu consistently enhanced type I collagen and glycosaminoglycan synthesis, modulated metalloproteinase activity, and promoted angiogenesis and cellular proliferation.

A second strand of the literature is transcriptional. The 2018 International Journal of Molecular Sciences review reports that GHK stimulates blood vessel and nerve outgrowth, increases collagen, elastin and glycosaminoglycan synthesis, and has antioxidant, anti-inflammatory, DNA-repair and proteasome-activating actions, with the widely quoted figure that it can up- or downregulate at least four thousand human genes. That claim is worth reading carefully: it comes from gene-expression and database analysis rather than from clinical endpoints, and much of the review literature on GHK comes from a small number of closely related author groups.

The unresolved practical question is delivery. The 2025 BioImpacts review notes that GHK is highly hydrophilic and unstable in formulation, which limits how much of it crosses intact skin, and that metal complexation and attaching a hydrophobic group such as a palmitoyl chain both increase permeability. The same review states plainly that there is a surprising absence of clinical studies using GHK-Cu and its palmitoylated derivative, which is the central gap between the volume of mechanistic work and the thinness of the human record.

Strength of evidence

Limited human dataFifty years of cell-culture and animal work sit on top of a very thin human record. A 2026 systematic review found only two randomised controlled trials among twenty studies, and reported that their combined clinical yield amounted to better patient-reported satisfaction after laser resurfacing and reduced wrinkle volume and depth; the review does not name those two trials in its abstract, and its full text could not be obtained, so they cannot be matched to the studies listed here. Of the controlled trials listed here, the 2006 facial trial was null on its blinded and computer-scored endpoints and the 1992 venous-ulcer trial found copper tripeptide cream indistinguishable from vehicle; the remaining human data come from a single uncontrolled study of a six-ingredient scalp injection. No human trial of injected GHK-Cu, the route the cheatsheet describes, was located at all.

Key studies

Review2026Aesthetic Surgery Journal
The Regenerative Potential of GHK-Cu in Aesthetic Medicine
A systematic review searching databases through March 2026 identified twenty studies, of which eighteen were preclinical and two were randomised controlled trials. Preclinical data consistently showed enhanced extracellular matrix synthesis, metalloproteinase modulation and angiogenesis, while the clinical findings amounted to improved patient satisfaction after laser resurfacing and reduced wrinkle dimensions. The authors concluded the evidence was constrained by methodological variability and a limited number of well-designed clinical trials.
Randomised controlled trial2006Archives of Facial Plastic Surgeryn = 13
Effects of topical copper tripeptide complex on CO2 laser-resurfaced skin
Thirteen patients who had circumoral carbon dioxide laser resurfacing were randomised to a post-treatment skin regimen with or without GHK-Cu. Computer analysis and blinded evaluators found no statistically significant difference in resolution of redness, and no significant difference in wrinkles or overall skin quality at twelve weeks. Only the patients' own questionnaire scores for overall skin quality favoured GHK-Cu (P = .04).
Randomised controlled trial1992Journal of Vascular Surgeryn = 86
A prospective randomized evaluator-blinded trial of two potential wound healing agents for the treatment of venous stasis ulcers
Eighty-six evaluable patients with venous stasis ulcers were randomised between 1 percent silver sulfadiazine cream, a 0.4 percent tripeptide copper complex cream and an inert vehicle placebo. Silver sulfadiazine statistically reduced ulcer size compared with both of the others, and there was no difference between the copper tripeptide cream and placebo.
Human trial2018Journal of Cosmetic and Laser Therapyn = 1000
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
An open-label pilot study injected a bioengineered scalp formulation containing vascular endothelial growth factor, basic fibroblast growth factor, insulin-like growth factor, keratinocyte growth factor, thymosin beta-4 and copper tripeptide-1 every three weeks for eight sessions. A significant reduction in hair fall on the hair pull test was seen in 83 percent of patients, with increased terminal hairs and shaft diameter, and a statistically significant increase in total hair count still present at one year (P = 0.002). There was no control group and copper tripeptide-1 was one of six active ingredients.
Review2025BioImpacts
Topically applied GHK as an anti-wrinkle peptide: Advantages, problems and prospective
A review of GHK as a topical anti-wrinkle ingredient concluding that cellular evidence supports the claim but that clinical investigation of GHK-Cu and its palmitoylated derivative is notably absent. It attributes the gap to the peptide's hydrophilic nature and instability, and notes that metal complexation, hydrophobic modification, cell-penetrating peptides and microneedle pretreatment all increase skin permeation.
Review2018International Journal of Molecular Sciences
Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data
A survey of GHK's reported actions across skin, lung, bone, liver and stomach tissue, describing stimulation of blood vessel and nerve outgrowth and of collagen, elastin and glycosaminoglycan synthesis, together with anti-inflammatory, antioxidant, DNA-repair and proteasome-activating properties. The evidence assembled is preclinical and gene-expression based rather than clinical.
Review2015BioMed Research International
GHK Peptide as a Natural Modulator of Multiple Cellular Pathways in Skin Regeneration
A review describing GHK as a plasma tripeptide that declines with age and functions as a copper(II) complex, stimulating both synthesis and breakdown of collagen and glycosaminoglycans, modulating metalloproteinases and their inhibitors, restoring replicative vitality to irradiated fibroblasts, and accelerating wound healing across skin, hair follicles, gastrointestinal tract and bone in rats, mice, pigs and dogs. It also states the claim that GHK can up- or downregulate at least four thousand human genes.
Animal study2015Journal of Orthopaedic Researchn = 72
Tripeptide-copper complex GHK-Cu (II) transiently improved healing outcome in a rat model of ACL reconstruction
Seventy-two rats undergoing anterior cruciate ligament reconstruction were randomised to saline or GHK-Cu at 0.3 or 3 mg/ml, injected into the joint weekly for four weeks. At six weeks the GHK-Cu groups had less side-to-side knee laxity than saline (p = 0.009) and the 0.3 mg/ml group had higher graft stiffness (p = 0.026), but there was no significant difference at twelve weeks and none in ultimate load, gait or histology. The benefit did not persist after treatment stopped.

Safety data

The published human safety record is quiet, but it is also very small. The 2006 carbon dioxide laser trial randomised thirteen patients and reported no treatment-related problems attributable to the GHK-Cu regimen, though its objective endpoints showed no benefit either. The 1992 venous ulcer trial ran 0.4 percent copper tripeptide cream against placebo in eighty-six evaluable patients and found the two indistinguishable. The 2018 scalp study is titled a safety and efficacy evaluation and followed patients for a year, but it was open-label, had no control arm, and tested copper tripeptide-1 as one component of a six-ingredient formulation, so it cannot isolate this peptide's risks. The 2026 systematic review in Aesthetic Surgery Journal set out to assess efficacy and safety and concluded that the findings across studies were constrained by methodological variability and by the small number of well-designed clinical trials.

The specific regulatory concern is about injection, which is the route the research-vial market uses and the one with no published human trial at all. The United States Food and Drug Administration states that compounded injectable drugs containing GHK-Cu may pose a risk for immunogenicity because of the potential for aggregation and peptide-related impurities, and that there are limited data in humans to inform safety-related considerations. That is a manufacturing and immune-response concern rather than a demonstrated toxic effect, but nothing in the literature closes it out.

Two mechanistic issues deserve naming. First, the peptide's whole function is to deliver copper, a metal the body regulates tightly, and no located human study has monitored serum copper, ceruloplasmin or zinc status during repeated dosing. Second, the reviews consistently describe GHK-Cu as pro-angiogenic and as a stimulator of cell proliferation, which is the standard reason for caution in anyone with a cancer history. Long-term use, repeated cycling and interactions with other medicines are unstudied.

Regulatory status

FDA: The United States Food and Drug Administration (FDA) has not approved GHK-Cu as a drug for any indication; it is marketed as a cosmetic ingredient under the name copper tripeptide-1, and the FDA's compounding pages record that compounded injectable drugs containing GHK-Cu may pose a risk for immunogenicity due to potential aggregation and peptide-related impurities, with limited human data to inform safety considerations.
WADA: GHK, GHK-Cu, copper peptide and copper tripeptide are not named anywhere on the World Anti-Doping Agency (WADA) 2026 Prohibited List, but because injectable GHK-Cu has no approval from any governmental regulatory health authority for human therapeutic use, an athlete injecting it would fall under the catch-all wording of class S0, non-approved substances, which is prohibited at all times.
Source: https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks

Open questions

Does injected GHK-Cu do anything measurable in a person? No human trial of the subcutaneous route has been published, and the cheatsheet figures come from practice rather than from dose-ranging work.
How much intact GHK-Cu actually reaches the dermis from a topical product, given that the 2025 BioImpacts review identifies permeation as the unsolved formulation problem?
Does GHK-Cu contribute anything on its own to hair regrowth, or was the effect in the 2018 scalp study driven by the five growth factors it was mixed with?
What happens to copper and zinc status over months of repeated injected dosing, which no located study has measured?
Do the four-thousand-gene expression findings translate into any clinical outcome, and would they replicate outside the small group of authors who generated them?