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Jump to: On the skin · By injection · Copper and your liver · Hair shedding · Evidence table · Who should be careful · Common questions
"Stings for a whole 24 hours... almost like a wasp or bee sting." That is how one Reddit user described injecting GHK-Cu, and the replies made it sound normal: "Oh you mean the single most common side effect of this peptide?"
That exchange captures the problem with GHK-Cu side effects. The most common experiences come from forums, not studies, because the injection that produces them has never been tested in a published human trial. Here is what is known, by route, and where the evidence stops.
On the skin: creams and serums
What the trials recorded. The human studies of GHK-Cu creams and gels were small and short, and none reported serious harms. They include:
- a placebo-controlled diabetic-ulcer trial (Mulder 1994, PMID 17147644)
- an 86-person leg-ulcer trial (Bishop 1992, PMID 1495150)
- a 13-person laser-resurfacing trial (Miller 2006, PMID 16847171)
Small trials can miss uncommon reactions.
What a lab test found. In a 2016 study of skin cells grown in a dish, GHK-Cu was not toxic to the cells and did not raise irritation markers. Simple copper salts at the same concentrations did (Li et al., 2016, PMID 27892491). That is a cell model, not skin on a person.
What users report.
- Irritation. "When I tried The Ordinary with copper peptide I got serious irritation."
- The "copper uglies." A Reddit term for skin looking worse (dull, rough, breakouts) after starting copper peptides. A 30PlusSkinCare thread is titled "Albeit rare Copper peptide 'uglies' are real and scary." We found no study that measured it.
- Mixing with other actives. Readers ask whether copper peptides clash with retinol, vitamin C and acids. We found no controlled study of these combinations on skin. Product labels often list what not to combine, so follow the label.
By injection
Most of the research so far comes from laboratory and animal studies. That does not tell us whether it works in people. For injected GHK-Cu, we also found no published human safety data.
What FDA says. FDA's safety summary says compounded injectable GHK-Cu "may pose risk for immunogenicity due to the potential for aggregation and peptide-related impurities," and notes "limited data in humans to inform safety-related considerations" (FDA). Immunogenicity means an immune reaction to the product. Aggregation means molecules clumping together, which can make that more likely.
What users report.
- Burning and stinging at the injection site lasting hours to a day.
- Welts "that linger for days."
- Mood dips after injecting: "My mood would just decline for an hour or two after."
These are anonymous user reports, often about products of unknown content. One user asked whether the burning meant "the one I'm taking is from a bad batch." Nobody can tell from a forum post.
What a clinician told NPR. A Seattle-area clinician said he has seen patients who injected grey-market GHK-Cu with elevated liver enzymes and elevated copper, and that it is unclear whether the peptide or an impurity caused it (NPR, Sep 7, 2026). That is one clinician's account, not a study.
What is in the vial. A dermatologist quoted by NPR put it plainly: "Whether or not it's even a copper peptide is always a concern." Straight Up Peptides has not tested any GHK-Cu product.
Copper and your liver
"Ghk-cu side effects liver" is one of the most common searches about this peptide, and the worry has a real basis.
Copper is an essential mineral, but too much of it over time can damage the liver and cause nausea, cramps, diarrhea and vomiting, according to the NIH Office of Dietary Supplements. ODS also says copper toxicity "is rare in healthy individuals who do not have a hereditary copper homeostasis defect." The adult upper limit for copper from food and supplements is 10 mg a day (NIH ODS copper fact sheet). That limit was set for copper you swallow. We found no published data on how much copper reaches the blood after injecting GHK-Cu.
Read this next GHK-Cu research profile
People with Wilson disease, a rare inherited condition, cannot clear copper normally and are at high risk of copper toxicity (MedlinePlus).
Kidneys and cancer. We found no human study of GHK-Cu and kidney function, and no human study of GHK-Cu and cancer risk in either direction. Claims that GHK "resets" cancer genes come from lab-grown cancer cells, as explained on our GHK-Cu profile.
Hair shedding
Hair-loss forums report shedding after starting copper peptides: "noticed instant shedding within a few days. I don't know if that's normal." Some minoxidil users see temporary shedding when starting that drug, and many GHK-Cu users stack the two, so it is hard to tell which one caused it. We found no controlled study of GHK-Cu for hair loss and no study measuring shedding.
Evidence table
| Side effect or concern | Route | Best evidence | What it shows |
|---|---|---|---|
| Serious harms | RouteTopical | Best evidence3 small human trials | What it showsNone reported; trials too small for rare events |
| Skin irritation | RouteTopical | Best evidenceCell study; user reports | What it showsLow irritation in cells; users report irritation |
| "Copper uglies" | RouteTopical | Best evidenceUser reports only | What it showsNot studied |
| Burning, welts | RouteInjection | Best evidenceUser reports only | What it showsNot studied |
| Immune reaction | RouteInjection | Best evidenceFDA safety assessment | What it showsPossible risk, not measured in people |
| Raised liver enzymes or copper | RouteInjection | Best evidenceOne clinician's account (NPR) | What it showsUnclear cause; not studied |
| Copper overload | RouteAny | Best evidenceNIH ODS (copper in general) | What it showsRare in healthy people; high risk in Wilson disease |
| Hair shedding | RouteTopical | Best evidenceUser reports | What it showsNot studied |
| Cancer, kidney effects | RouteAny | Best evidenceNone found | What it showsUnknown |
Who should be especially careful
- People with Wilson disease or other copper-handling disorders.
- People with liver disease.
- Pregnant or breastfeeding people: no safety data.
- People with a copper allergy or reactive skin.
We did not find reliable interaction data in the sources reviewed. That does not mean there are no interactions. Talk to a licensed clinician about any symptoms.
Status, in brief
GHK-Cu is not an FDA-approved drug. Creams sell legally as cosmetics. Injectable GHK-Cu is off FDA's compounding lists, and Health Canada has seized injectable GHK-Cu and recalled powder lots. The full breakdown is in is GHK-Cu FDA approved?.
If you use copper peptides on your skin. Patch-test a new serum on a small area for a few days. Start with a product that states its concentration ("The Ordinary is the only one that tells the percentage," one reader noted). Compare copper serums by stated GHK-Cu %.
- The Ordinary Multi-Peptide + Copper Peptides 1% Serum, about $32 for 30 mL (check current price)
- NIOD Copper Amino Isolate Serum 3:1, about $62 for 15 mL (check current price)
We may earn a commission from these links. These are cosmetics, not treatments.
Common questions
What are the side effects of GHK-Cu?
On the skin, users report irritation and a temporary worsening called the "copper uglies," and the small human trials reported no serious harms. Injected GHK-Cu has no published human safety data. Users report burning and welts, and FDA flags a possible immune-reaction risk.
Does GHK-Cu damage your liver?
No study has measured this. Too much copper can harm the liver over time, according to NIH. One clinician told NPR he has seen raised liver enzymes and copper in people who injected grey-market GHK-Cu, with the cause unclear.
What are the "copper uglies"?
It is a Reddit term for skin looking worse after starting copper peptides. Users describe dullness, roughness or breakouts. We found no study that measured it.
Why does GHK-Cu burn when injected?
No study has examined it. Users widely report burning and welts. FDA has raised concerns about impurities and clumping in injectable GHK-Cu, and the content of grey-market vials is unverified.
Can GHK-Cu cause hair shedding?
Some users report shedding after starting it, often while also using minoxidil, which can cause shedding itself. No study has measured shedding with GHK-Cu.
Is GHK-Cu bad for your kidneys?
We found no human study of GHK-Cu and kidney function, so the answer is unknown.
Can you use copper peptides with retinol or vitamin C?
We found no controlled study of these combinations on skin. Follow the product label, and patch-test any new combination. The label comparison is copper peptides vs retinol.
Sources, methodology, and changes
Methodology. Literature search on 2026-10-10: PubMed (GHK-Cu, copper peptide, copper tripeptide with irritation, dermatitis, allergy, adverse and zinc), FDA compounding safety-risk page, NIH ODS copper fact sheet, MedlinePlus, NPR's September 2026 report. Reader quotes come from Reddit threads collected for our reader research. They describe what people report and are not evidence of cause.
Primary sources.
- Mulder GD et al., 1994: PMID 17147644
- Bishop JB et al., 1992: PMID 1495150
- Miller TR et al., 2006: PMID 16847171
- Li H et al., 2016, Sci Rep (keratinocyte irritation model): PMID 27892491
- FDA, bulk drug substances that may present significant safety risks: https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- NIH Office of Dietary Supplements, Copper fact sheet (updated Oct 18, 2022): https://ods.od.nih.gov/factsheets/Copper-HealthProfessional/
- MedlinePlus Genetics, Wilson disease: https://medlineplus.gov/genetics/condition/wilson-disease/
- NPR, Sep 7, 2026: https://www.npr.org/2026/09/07/nx-s1-5955552/copper-peptides-skin-aging-health-safe
Changes. Oct 10, 2026: first published.
