What it is
GHK-Cu is a small tripeptide, glycyl-L-histidyl-L-lysine, bound to a copper(II) ion. The peptide on its own is GHK; the copper complex is GHK-Cu. It was first identified by Loren Pickart in 1973 in human plasma, where its concentration falls with age. It is best understood as a copper-delivery and tissue-signalling molecule rather than a hormone.
Two very different routes get discussed, and they are not interchangeable:
- Topical (creams and serums) is the route with the longest track record and is what most cosmetic research covers.
- Injectable (subcutaneous) is used in the research and self-experiment community for systemic effects, and has far less human safety data behind it.
What people use it for
Topically, the interest is skin quality: firmness, fine lines, collagen density, wound and scar appearance, and as a hair and scalp support. Injectable use is explored for broader tissue repair, recovery and connective-tissue support. The skin claims are the better supported of the two.
Typical dose range
Topical: concentrations of roughly 0.1 to 1 percent in a serum or cream, or about 2 to 4 mg/mL, are the commonly described cosmetic range and tend to be well tolerated on skin.
Injectable: the community range described is roughly 1 to 2 mg subcutaneously, a few times per week, sometimes cited as low as 0.5 mg. Be clear-eyed that injectable dosing is not backed by formal human dose-finding studies; the numbers circulating are convention, not established safe doses. Copper is biologically active and not benign in excess, so more is not better here.
If you are reconstituting an injectable vial, get the concentration and dose right rather than guessing: Peptide Calculator - Reconstitution & Dosage | Buy Peptides UK
Half-life and frequency
Free GHK and GHK-Cu are cleared from circulation quickly (on the order of minutes once in the bloodstream), with downstream signalling effects outlasting the molecule itself. Topical formulations are typically applied once or twice daily as part of a routine. Injectable protocols, where used, lean on a few-times-weekly cadence rather than relying on a long circulating presence.
Reconstitution (typical)
For injectable powder: bring the lyophilised vial to room temperature, add bacteriostatic water slowly down the vial wall, and swirl gently rather than shaking. GHK-Cu carries a distinctive deep blue colour from the copper, which is expected and not a sign of a problem. Decide your target concentration before adding water so the dose maths works out: Peptide Calculator - Reconstitution & Dosage | Buy Peptides UK
Topical products are usually bought pre-formulated; home-mixing into a cream introduces stability and contamination variables that are hard to control.
Storage
Lyophilised powder: store cold and dark, frozen at around -20 C for the long term. Reconstituted injectable solution: refrigerate at 2 to 8 C, keep out of light, and use within about 28 days. Do not freeze a reconstituted vial. Topical serums: follow the product’s own guidance, keep them out of heat and light, and note that copper formulations can discolour over time.
Common side effects
Topical use has a long and reassuring track record. Documented issues are mostly minor:
- A temporary breakout or skin purge in a minority of people in the first 2 to 3 weeks
- Local irritation, redness or contact sensitivity in some users
Injectable use has thinner human safety data. Reported and commonly described effects include:
- Injection-site redness or reaction
- A warm flushing sensation in the face, neck or chest shortly after injecting, usually fading within half an hour
The broader caution with the injectable route is systemic copper load. People with Wilson’s disease (a copper-handling disorder) should avoid it outright. It is generally avoided in active cancer, pregnancy and breastfeeding, and is not for under-18s.
Stacking and co-solubility
A practical co-solubility note: copper can oxidise and interact with other compounds, so GHK-Cu is generally kept in its own vial and its own injection rather than mixed in the same syringe with other peptides. Topically, copper peptides and strong direct acids (such as high-strength vitamin C) are often applied at different times of day on the theory that they can interfere; this is a formulation convention more than a proven interaction. There is no solid human evidence establishing any particular GHK-Cu stack as superior.
Evidence grade (human RCT / small human / animal-only / anecdote)
Mixed, and route-dependent.
- Topical skin quality: small human studies. There are placebo-controlled cosmetic studies and a small modern topical trial (around 21 women) reporting increased skin collagen density. These are small and mostly industry-adjacent, but they are real human data on skin endpoints.
- Wound healing and systemic repair: largely animal-only. Faster wound contraction and improved healing were shown in rats, mice, rabbits and pigs, including effects at sites distant from injection. Strong mechanism story, thin human outcome data.
- Mechanism (gene modulation): Pickart’s group reported GHK shifting the expression of thousands of genes toward a more youthful pattern. This is interesting mechanism evidence, not proof of a clinical outcome.
- Injectable use in humans: mostly anecdote. Dosing and safety for the injected route rest on community reports rather than trials.
Honest unknowns
- The systemic safety of repeated injectable GHK-Cu in humans, including cumulative copper exposure, is not well characterised.
- How well the topical skin findings translate to the injected systemic claims is genuinely unknown; they are different exposures.
- Optimal dose, frequency and cycle length for injectable use are not established by any controlled human study.
- The interaction between active cancer and a molecule that promotes tissue growth and angiogenesis is a theoretical concern that has not been resolved, which is why caution there is standard.
Research use only. Not medical advice. 18+.