GHK-Cu: the copper peptide.

Unlike most research peptides, GHK-Cu is something your body already makes — a small tripeptide naturally found in human plasma. Its production declines sharply with age, which is why supplementing it has become one of the most-researched ideas in skin and tissue health.

What it actually is

GHK-Cu is a very small peptide — just three amino acids (glycine-histidine-lysine), bound to a single copper ion. It was first isolated from human plasma in the 1970s, and researchers noticed it could promote healing in liver tissue.

The most distinctive thing about GHK is that it binds copper extremely tightly. Copper is an essential trace mineral involved in dozens of biological processes — collagen formation, antioxidant defense, tissue repair — and GHK appears to act partly as a copper-delivery system, getting the mineral into cells that need it.

In the body, plasma levels of GHK drop substantially as we age — by some estimates dropping by half between age 20 and age 60. That decline parallels much of the visible aging in skin, hair, and tissue repair capacity, which is part of what has driven so much research interest.

What research has explored

GHK-Cu has one of the deeper research foundations among peptides commonly discussed in the community. Studies have looked at:

• Wound healing — promoting tissue regeneration in cuts, burns, and surgical wounds.
• Skin health — stimulating collagen and elastin production; reducing visible signs of aging.
• Hair growth — increasing follicle size and reducing hair loss in some studies.
• Anti-inflammatory effects — modulating inflammation in tissue injury models.
• Gene expression — a 2010 study found GHK could influence the expression of thousands of genes, many associated with tissue repair and stress response.

The injection site reality

If you spend any time in peptide communities, you will eventually hear about GHK-Cu's reputation: it can sting and cause welts, particularly when injected subcutaneously into the abdomen. This is one of the most consistently reported reactions to any research peptide.

It is the copper component that is generally suspected. Many users report better tolerance when injecting into the thigh or back of the arm instead, when letting the solution reach room temperature first, and when pushing slowly. None of this is medical guidance — just observations from the community.

Where it stands

Among research peptides, GHK-Cu has a relatively strong research foundation — it has been studied for decades, and it is one of the few where the natural human version's biological role is reasonably well-understood. That does not make injectable use approved or risk-free, but it does mean the underlying science is less speculative than for newer compounds.

For the dosing math, the calculator handles GHK-Cu specifically (a 50mg vial in 5mL bacteriostatic water is a common reference). The injection site map shows the alternative sites the community commonly uses for it.