GHK

GHK is the plain, uncomplexed tripeptide glycyl-L-histidyl-L-lysine — three amino acids (glycine, histidine, lysine) linked in sequence. It is not the same substance as GHK-Cu, the blue copper complex most peptide products actually contain and that most published research and skincare marketing describes. GHK’s natural biological role is largely as a copper-binding molecule: in the body it readily chelates copper ions to form GHK-Cu, and it is GHK-Cu, not free GHK, that carries most of the documented wound-healing and skin-related research. This entry covers the free tripeptide itself and where its evidence base does, and does not, overlap with GHK-Cu.

Research snapshot

Peptide category	Naturally occurring human tripeptide (copper-free form; distinct from the GHK-Cu copper complex)
Primary research interest	Native copper-binding/transport chemistry; most “GHK” skin and wound-healing research actually applies to GHK-Cu, not the free peptide
Highest available evidence	Discovery-era human plasma/tissue observational work and laboratory biochemical characterization; little to no evidence specific to the uncomplexed form
Human research available	Limited — no dosing data specific to the copper-free peptide identified; nearly all human research on “GHK” is actually research on GHK-Cu
Development status	Not in active pharmaceutical development as a distinct entity from GHK-Cu; sold as a research chemical/cosmetic ingredient
Regulatory status	Not approved as a drug by the FDA, EMA, or any other regulator
Last reviewed	September 27, 2026

Technical identity

Primary name	GHK
Alternative names	Gly-His-Lys; Glycyl-L-histidyl-L-lysine; GHK Basic (brand); Tripeptide-1 (code name for the acetate-salt form)
Peptide sequence	H-Gly-His-Lys-OH
Amino-acid length	3 residues
Molecular formula	C14H24N6O4 (free base, per ChemSpider); the commercial acetate-salt form (CAS 72957-37-0) is separately listed as C16H28N6O6
Molecular weight	~340.4 g/mol (free base); ~400.44 g/mol as listed for the acetate-salt form under CAS 72957-37-0
CAS Registry Number	72957-37-0 (acetate-salt form, marketed as “Tripeptide-1″/”GHK Basic”; not to be confused with CAS 49557-75-7, which is GHK-Cu, a separate substance)
PubChem CID	Not reliably established — direct PubChem verification was not possible during this research pass
UNII	Not established
DrugBank ID	Not established
Chemical modifications	None in the free base; typically sold commercially as an acetate salt
Peptide class	Naturally occurring copper-binding human tripeptide
Primary biological target	Copper(II) ions — GHK chelates Cu2+ via its histidine imidazole nitrogen, N-terminal amino group, and backbone amide nitrogen, spontaneously forming GHK-Cu
Developer or originator	First identified by Loren Pickart and colleagues in the early 1970s from human plasma and liver tissue
Development status	Discovery-era peptide; not pursued as a distinct pharmaceutical entity separate from GHK-Cu

What it is

GHK (glycyl-L-histidyl-L-lysine) is a naturally occurring human tripeptide first identified in the early 1970s by researcher Loren Pickart and colleagues, who isolated a small peptide fraction from human plasma and liver tissue that stimulated growth and improved survival of liver cells in culture. That fraction was subsequently characterized as the tripeptide GHK. It was later found that GHK has a strong natural affinity for copper(II) ions and, under physiological conditions, spontaneously forms a 1:1 complex with copper known as GHK-Cu (also called Copper Peptide GHK-Cu or, commercially, “Copper Peptide”). Because this copper-bound form is both the biologically dominant form in tissue and the form almost universally used in commercial skincare and injectable/topical peptide products, the large majority of published GHK-related research — including most of the studies people encounter when searching “GHK peptide” — is actually research on GHK-Cu, not on the free, uncomplexed tripeptide.

Reported human plasma concentrations of GHK are described in the peptide’s discovery-era and later literature as declining with age — young adult plasma has been reported to contain higher levels of the peptide than plasma from older adults — which is part of why GHK/GHK-Cu attracted interest as a potential marker or driver of tissue aging and regenerative capacity. This entry focuses specifically on the free tripeptide: its own chemical identity, its native copper-binding role, and what is and is not separately established for the uncomplexed form as opposed to GHK-Cu. Free GHK is sold commercially as a research chemical and cosmetic ingredient (sometimes marketed as “GHK Basic” or “Tripeptide-1” to distinguish it from copper-bound products), typically as a white powder intended for reconstitution or direct formulation, without added copper.

Because GHK and GHK-Cu are frequently used interchangeably (and sometimes conflated) in vendor and consumer-facing marketing, this entry classifies claims that are specific to the copper complex as belonging to GHK-Cu’s own separate entry, and only describes what applies to, or is specifically documented for, the free peptide itself.

How does it work?

Plain-English explanation

Think of GHK as a small molecular “hook” that the body uses to grab and carry copper, a trace mineral needed for wound healing, blood vessel formation, and the enzymes that build and repair connective tissue. On its own, GHK is a small building-block-sized peptide; once it binds copper, the resulting GHK-Cu complex is thought to be the more biologically active form that interacts with skin and tissue-repair processes. Because commercial peptide products are typically the copper-bound form, the specific biological actions attributed to “GHK” in most skincare marketing are actually actions documented for GHK-Cu, not the plain tripeptide by itself.

Technical explanation

GHK has the sequence Gly-His-Lys (H-Gly-His-Lys-OH), with a free-base molecular formula reported in chemical databases (e.g., ChemSpider) as C14H24N6O4. The commercially available form of the uncomplexed peptide is commonly sold and characterized as its acetate salt, for which a chemical-database entry (CAS 72957-37-0, listed under the trade name “Tripeptide-1”) gives a differing formula, C16H28N6O6, and molecular weight 400.44 g/mol — reflecting the added acetate counter-ion rather than a different peptide. The histidine imidazole nitrogen, the alpha-amino nitrogen of the N-terminal glycine, and the peptide backbone amide nitrogen together form a square-planar coordination site with high affinity for Cu2+, which is the structural basis for GHK’s native copper-chelating behavior and its spontaneous conversion to GHK-Cu in copper-containing biological fluids such as plasma. Most of the receptor-level, gene-expression, and collagen-stimulation mechanisms described in the GHK/GHK-Cu literature (e.g., effects on integrin signaling, tissue remodeling gene expression panels reported by Pickart and colleagues) were characterized using the copper complex, and it is not established that the uncomplexed peptide produces equivalent effects independent of copper binding.

Potential benefits and research applications

Natural copper transport and homeostasis (native biological role)

What is being investigated: GHK’s physiological role as an endogenous copper-binding peptide involved in copper transport and delivery to tissues. How the effect might occur: high-affinity chelation of Cu2+ via its histidine and terminal amino groups. Evidence: this role is described in the foundational discovery-era literature isolating GHK-like activity from human plasma and liver tissue, and in later reviews of copper-peptide biology. Strength: this is a laboratory/biochemical characterization finding (Tier 4) combined with older human plasma/tissue observational work (Tier 2-3 depending on the specific study); it describes GHK’s native chemistry rather than a therapeutic claim. Limitation: precise, modern, independently replicated pharmacokinetic data on free GHK’s copper-binding behavior in living human tissue (as opposed to in vitro chemistry) is limited.

Skin and wound-related effects claimed for “GHK” in commercial marketing

What is being investigated: collagen stimulation, wound healing, and skin-firmness effects commonly attributed to “GHK” peptide products. How the effect might occur: proposed via copper-dependent enzymatic activity (e.g., lysyl oxidase, involved in collagen cross-linking) and copper-dependent gene-expression modulation. Evidence: the substantial majority of the published human, animal, and cell studies supporting these effects were conducted with GHK-Cu, the copper complex, not the free tripeptide; see the separate GHK-Cu entry on this site for that evidence base. Strength: as applied specifically to the uncomplexed free peptide, evidence is sparse to essentially absent — this benefit set has not been established as separately reproducible using GHK without bound copper. Limitation: marketing and vendor material frequently describes “GHK” benefits without distinguishing the free peptide from GHK-Cu, which this entry treats as a meaningful evidence-transfer gap rather than a confirmed property of the uncomplexed peptide.

What dosage information circulates?

Figures in this section summarize amounts and schedules reported in published research or circulating online. Their inclusion documents what is reported and does not establish that a regimen is verified, safe, effective, or appropriate.

Reported use or research objective	Route reported	Amount reported	Frequency reported	Reported duration	Evidence or source category
Human research (free, copper-free GHK specifically)	Not applicable	No established or reliably sourced dosing information was identified	Not applicable	Not applicable	Human studies of “GHK” identified in the literature studied GHK-Cu, not the free peptide
Animal research (free GHK specifically)	Not applicable	Not established	Not established	Not established	Animal studies of “GHK” identified predominantly used the copper-bound form
Cosmetic formulation use (community/vendor, copper-free form)	Topical	Low single-digit percentage in formulation, consistent with general cosmetic-peptide practice	Not consistently reported	Not consistently reported	Vendor reported — not clinically validated dosing

Amounts studied in human research

No established or reliably sourced dosing information specific to the uncomplexed (copper-free) GHK tripeptide, administered as such in a human clinical study, was identified. Human studies identified in the literature reviewed for this entry studied GHK-Cu (the copper complex), not free GHK, so those figures belong to the GHK-Cu entry rather than this one.

Amounts studied in animal research

No established or reliably sourced dosing information specific to the uncomplexed GHK tripeptide in animal models was identified during this research pass. As with human data, animal studies of “GHK” identified in available literature predominantly used the copper-bound form.

Practitioner and community-reported protocols

Vendor and cosmetic-formulation sources selling “GHK Basic” or “Tripeptide-1” (the copper-free form) as a research or cosmetic-formulation ingredient describe typical topical formulation usage rates in the low single-digit percentage range, consistent with general cosmetic-peptide formulation practice, but these are vendor-reported formulation guidelines, not clinically validated dosing, and no consistent, independently sourced figure specific to the free peptide could be verified. Not consistently reported.

Side effects, risks, and limitations

No dedicated, independent human safety or adverse-event study specific to the uncomplexed GHK tripeptide (as distinct from GHK-Cu) was identified. General limitations applicable to any unregulated topical or “research” peptide apply: purity, concentration accuracy, and contamination cannot be assumed for bulk peptide powders purchased outside a regulated pharmaceutical or cosmetic-ingredient supply chain. Because free GHK is chemically primed to bind copper on contact with copper-containing solutions or biological fluids, product labeled and sold as “free GHK” may convert, at least partially, to GHK-Cu once formulated or once it contacts tissue, which is a practical consideration for anyone trying to study or use the two forms as distinct substances. Long-term safety data specific to sustained exposure to the free, non-copper-bound peptide has not been established independently of the GHK-Cu literature.

Regulatory and developmental status

Free GHK has not been approved as a drug by the FDA, EMA, or any other pharmaceutical regulator, and is not being pursued through pharmaceutical development as a distinct entity separate from GHK-Cu, based on the sources reviewed for this entry. It is sold commercially as a research chemical and, in some cases, as a cosmetic-formulation ingredient in its copper-free acetate-salt form. Its regulatory status therefore mirrors that of many unapproved research peptides: legally available for research/cosmetic formulation use in many jurisdictions, but not an approved or regulated therapeutic agent. Status verified as of the date this entry was checked.

Frequently asked questions

What is GHK?

GHK is the plain tripeptide glycyl-L-histidyl-L-lysine, a naturally occurring human peptide first identified in plasma and liver tissue, best known for its strong natural ability to bind copper.

Is GHK the same as GHK-Cu?

No. GHK is the uncomplexed, copper-free tripeptide. GHK-Cu is the copper(II) complex formed when GHK binds a copper ion. GHK-Cu, not free GHK, is the form used in almost all commercial skincare/injectable peptide products and is the subject of the large majority of published research; this site’s separate GHK-Cu entry covers that evidence base.

Does GHK naturally bind copper in the body?

Yes. GHK has a high natural affinity for Cu2+ and is understood to spontaneously form GHK-Cu under normal physiological conditions, which is central to its biological role as originally described in the discovery literature.

Do the benefits reported for GHK-Cu also apply to free GHK?

This has not been established. Most of the collagen-stimulation, wound-healing, and gene-expression research widely cited for “GHK” was conducted using the copper-bound complex, not the uncomplexed peptide, and this entry does not assume those effects transfer to the free form without independent evidence.

What dosage of GHK has been studied?

No established or reliably sourced human or animal dosing data specific to the uncomplexed GHK tripeptide was identified. Available dosing literature on “GHK” almost universally refers to studies of GHK-Cu.

Is GHK approved by the FDA?

No. Free GHK has not been approved as a drug and is not in active pharmaceutical development as a distinct product separate from GHK-Cu.

Why do plasma GHK levels matter?

Early discovery-era research reported that GHK-related activity in human plasma appeared lower in older adults than in younger adults, which helped generate interest in GHK/GHK-Cu as a potential marker of, or contributor to, age-related changes in tissue-repair capacity; this remains an area associated mostly with older, discovery-phase literature rather than modern controlled trials of the free peptide.

Is free GHK safe to use?

No dedicated independent safety study specific to the copper-free form was identified. General cautions for unregulated research peptides (purity, accurate concentration, and potential unintended conversion to GHK-Cu on contact with copper) apply.

Bottom line

GHK is a real, naturally occurring human tripeptide whose defining, best-established biological property is its strong natural affinity for copper — a property that leads it to convert into GHK-Cu, the form that carries almost all of the published skin, wound-healing, and gene-expression research associated with the “GHK” name. Very little evidence exists that is specific to the uncomplexed, copper-free peptide itself, and no reliable human or animal dosing data for the free form was identified. Readers researching GHK for its reported anti-aging or skin benefits should understand that the great majority of that evidence base actually describes GHK-Cu, covered separately on this site, and should not assume the two forms are interchangeable in their documented effects.