DOSAGE RESEARCH / 03
GHK-Cu dosage in the research record: concentrations, routes and stability
What was administered, to which species, by which route — the studied concentrations and the delivery chemistry, with no recommendation for any person.
The studied concentration ranges
GHK-Cu dosage in research spans a wide ladder because the molecule has been tested in cell culture, topical formulations and rodent systemic models — none of which translate to a human dose. In human fibroblast cultures the active range for collagen synthesis was 10^-12 to 10^-9 M, with onset at 10^-12 to 10^-11 M and peak near 10^-9 M [1]. Topical cosmetic and clinical formulations have used roughly 0.05% to 2% (w/w) in creams, serums and gels.
Rodent systemic studies used far higher loads by injection: mouse pulmonary models dosed 0.2 to 20 micrograms per gram per day intraperitoneally, silicosis models used 2 and 20 mg/kg, a colitis model used 20 mg/kg by oral gavage, and aging-cognition models used 15 mg/kg intranasally. The single controlled human hair study applied a 5-ALA + GHK combination topically at 50 to 100 mg/mL [4]. These figures are descriptions of experiments, not instructions; the framing throughout is studied at X in a named species or model.
Half-life and the dermal depot
No rigorous human pharmacokinetic half-life has been published for GHK-Cu. The free tripeptide (340.38 Da) is rapidly cleared by plasma peptidases, and a rat HPLC study documented rapid metabolism of GHK to the dipeptide HK after intravenous dosing. Secondary literature cites a short systemic elimination half-life on the order of 1 to 2 hours, with the copper-chelated complex more stable than free GHK.
Topically the picture is different. In a human skin penetration study, copper applied as the GHK-Cu tripeptide crossed dermatomed skin with a permeability coefficient of 2.43 x 10^-4 cm/h; over 48 hours 136.2 micrograms per square centimeter of copper permeated and about 97 micrograms per square centimeter was retained as a dermal depot [5]. That depot behavior is why topical formulations are designed around prolonged local availability rather than a single systemic peak. There are no validated human pharmacokinetic data for injectable or systemic GHK-Cu, which remains research-only.
Stability, delivery and what disrupts the complex
The GHK-Cu complex is most stable near pH 5 to 6.5 at a 1:1 copper-to-peptide ratio, and its high copper stability constant (log K around 16.4) keeps free-copper release low [3]. The blue-violet color of a reconstituted solution is the expected Cu(II) absorption and indicates an intact complex; a brown or green shift indicates oxidation or precipitation. Strong reducing agents — ascorbic acid below about pH 3.5 — reduce Cu(II) and break the complex, and low-pH acids (AHAs and BHAs) can destabilize it or compete for the copper.
Delivery is the central topical constraint. Free GHK is highly hydrophilic (clogP -2.24), which limits passive stratum-corneum penetration; a 2025 review identified that permeability as the core challenge and evaluated palmitoylation (Pal-GHK, clogP about 1.14) and microneedle pretreatment — through which roughly 134 nmol of GHK permeated, versus none through intact skin — as enhancement strategies [8]. The throughline is that the copper chemistry that makes GHK-Cu work is the same chemistry that makes it fragile, and the literature treats formulation as inseparable from efficacy.