GHK-Cu dosage research and half-life
The most consequential blank in the safety file is human exposure. Concentration, a blood half-life and copper retained in skin each describe a different quantity.
GHK-Cu half-life in humans
A validated human pharmacokinetic half-life for injectable or systemic GHK-Cu has yet to be published. The frequently repeated estimate of 1–2 hours appears in secondary literature, with an unclear basis for applying it to human GHK-Cu injections. Giving that estimate the status of a measured human result would misrepresent the source.
The 1997 rat plasma study tracked free GHK after intravenous administration. It documented rapid metabolism to histidyl-lysine, or HK, a shorter peptide. Copper-free GHK was the starting material. GHK-Cu is a different complex, and the species was rat.
Half-life means the time over which a measured amount falls by half. Without a validated human measurement, a proposed injection interval rests on assumptions about both the material and the body handling it. The source record supports no human schedule.
Experimental GHK-Cu amounts
The studies below describe their own experimental conditions. I resist arranging them into a single ladder of stronger and weaker treatments: their units and settings differ.
| Setting | Material and amount reported | Outcome or purpose |
|---|---|---|
| Human fibroblast culture | GHK-Cu, onset at 10^-12 to 10^-11 M; peak near 10^-9 M | Collagen synthesis |
| Topical formulation literature | GHK-Cu, roughly 0.05% to 2% by weight | Cosmetic preparations |
| Human scalp trial | 5-aminolevulinic acid plus free GHK, 50 mg/mL and 100 mg/mL | Hair counts |
| Mouse scalp experiment | GHK-Cu, 2% in a specialised microemulsion | Follicle growth and hair density |
The fibroblast concentrations, topical formulation range, human combination preparations and mouse microemulsion come from different experiments. These entries carry no instruction for use in people. In particular, the human scalp concentrations refer to the combination tested there.
The local copper depot
After 48 hours in the excised-skin penetration experiment, the retained copper depot was 97 ± 6.6 µg/cm². That observation describes local copper retention in a tissue sample. It supplies neither a blood half-life nor an application interval for living skin.
I trust that sentence only while its quantity stays named exactly. “The local copper depot” makes a much smaller claim than “GHK-Cu lasts this long,” and the experiment measured the former.
The missing exposure record
The skin literature contains small topical human studies. No completed Phase 2 or 3 trials establish systemic or injectable GHK-Cu treatment, and validated human measurements of bioavailability, peak concentration and tissue distribution remain absent.
That gap matters to safety as much as to benefit. Repeated systemic exposure raises a theoretical concern about copper accumulation and copper–zinc balance, while published human copper-toxicity cases attributed to GHK-Cu are absent from the reviewed record. I see an unanswered exposure question here; neither a dosing calculation nor an all-clear follows from it.