# GHK-Cu Dosage in Research: Concentrations, Routes, Half-Life > GHK-Cu dosage as studied in research: the picomolar collagen range, topical 0.05-2% formulations, rodent routes, and why no validated human half-life exists. What concentrations and routes appear in the studies — read as a record of what was administered to which model, never as a human dosing recommendation. ## GHK-Cu dosage in the research record GHK-Cu dosage in the literature spans an enormous range because the studies span cell culture to whole animals. This section describes what was administered in which model — it is not a human dosing recommendation, and no validated human protocol exists [3]. The most precise numbers come from cell culture. In human fibroblasts, collagen synthesis began between 10^-12 and 10^-11 M and peaked near 10^-9 M — picomolar-to-nanomolar, far below anything a topical product delivers [1]. That picomolar potency is one of the more striking facts in the record: the active concentration in a dish is vanishingly small, even though getting that much to the right place in living tissue is the hard part [1][5]. Topical cosmetic and clinical formulations sit around 0.05% to 2% (w/w) in creams, serums, and gels [3]. The human hair-loss trial used a 5-ALA-plus-GHK topical at 50-100 mg/mL [4], and the 2024 mouse hair study used a 2% GHK-Cu microemulsion [14]. These are concentrations in a formulation, not the concentration that reaches the target cells, which is far lower after the molecule crosses skin [5]. Rodent systemic studies used much higher loads by injection: mouse pulmonary models dosed 0.2-20 ug/g intraperitoneally on alternate days, pulmonary-fibrosis models used 2.6-260 ug/mL/day, silicosis models used 2-20 mg/kg, a colitis model used 20 mg/kg oral gavage daily, and intranasal cognitive studies used 15 mg/kg daily or three times weekly [3]. Rat behavioral studies used roughly 0.5 ug/kg to 0.5 mg/kg intraperitoneally [3]. These are research doses in animals, not a guide for people. ## Half-life and pharmacokinetics No rigorous human pharmacokinetic half-life has been published for GHK-Cu [3]. The free tripeptide (340.38 Da) is rapidly cleared by plasma peptidases: a rat HPLC study documented GHK being metabolized to the dipeptide histidyl-lysine after intravenous dosing, which is the closest peer-reviewed pharmacokinetic data available [12]. Secondary literature cites a short systemic elimination half-life on the order of 1-2 hours, with the copper-chelated complex more stable than free GHK [3]. Topical application behaves differently: it forms a dermal copper depot, with about 97 ug/cm^2 retained over 48 hours, giving prolonged local availability even though systemic kinetics are fast [5]. The split between rapid plasma clearance and a persistent skin depot is the central pharmacokinetic fact, and the absence of validated human numbers is the central gap. ## Routes studied The route list reflects the delivery problem at the heart of GHK-Cu research. Topical is dominant — creams, serums, liposomes, nano-lipid carriers, ionic-liquid microemulsions, wound dressings, and nanofibers — because the molecule's job in skin and hair is local [13][14]. The 2024 mouse hair study used an ionic-liquid microemulsion specifically to overcome poor penetration [14]. Systemic routes appear in animal work: intraperitoneal for rodent pulmonary and behavioral studies, intranasal for rodent cognition, oral gavage for colitis, and intravenous or subcutaneous for pharmacokinetic studies [3][12]. Hair studies have also used intradermal and microneedle delivery to get the peptide past the stratum corneum [13]. Across every systemic route, the human pharmacokinetic data simply has not been collected — these remain research routes [3]. ## What has actually been dosed in people For a site reading this carefully, the human side of the dosage question deserves its own honest summary. Human evidence is predominantly topical and dermatologic: small placebo-controlled facial cream and serum trials (roughly n=20-71) reporting improved skin density, firmness, fine lines, and wrinkle depth, plus the 6-month, 45-man hair-loss trial of a 5-ALA-plus-GHK combination [3][4]. There are no completed Phase 2 or Phase 3 trials for systemic or injectable GHK-Cu, and a topical wound-healing trial has been registered [3]. Injectable and systemic dosing protocols circulating in community contexts have no peer-reviewed human pharmacokinetic basis [3]. So the honest dosage picture is this: well-characterized at the cosmetic-topical level, and effectively uncharacterized in humans by any systemic route. Anyone reading a systemic protocol should know it rests on animal data and inference, not human trials [3][12]. ## Stability and the form that was used Stability is part of any honest dosage discussion for GHK-Cu, because the complex can break. It is most stable near pH 5-6.5 at a 1:1 copper-to-peptide ratio, and its high stability constant (log K around 16.4) keeps free copper low [3]. Strong reducing agents — ascorbic acid below about pH 3.5 — reduce the copper(II) and break the complex, and AHAs and BHAs can destabilize it or compete for copper [13]. The form a study used matters as much as the dose. GHK is the free tripeptide; GHK-Cu is the copper chelate, and copper coordination is required for most documented bioactivities [2]. Many studies report on the free peptide and observe systemic or gene-level effects, so reading the dose without reading the form can mislead — a recurring theme across the [GHK-Cu research findings](/research). --- A still, careful reading of the GHK-Cu copper-peptide record — each finding set down beside its gap, cited to source, with no clinic in the room and nothing here to sell.