Where the '95% pure' number for GHK-Cu comes from
The quick version
You will often see it said that commercial GHK-Cu is about 95% pure.
That number comes from a 2014 safety review — which attributes it to GHK, a different molecule, in its main text, and to GHK-Cu in its summary.
The document contradicts itself, and the summary is the part people read.
Search for GHK-Cu and a number follows you around. Roughly 95% pure. It gets repeated in product descriptions, forum posts and buying guides, usually with no source attached, in the tone of a known specification.
We went looking for where it came from. The answer turned out to be more interesting than the number.
The trail leads to one document
It traces to a 2014 safety review by the Cosmetic Ingredient Review. That is an industry-funded panel. It reviews cosmetic ingredients and publishes what it finds.
The review does not cover one ingredient. It covers three:
| Ingredient | What it is |
|---|---|
| Tripeptide-1 | GHK — the plain peptide, no copper |
| Copper tripeptide-1 | GHK-Cu — the peptide bound to copper |
| Palmitoyl tripeptide-1 | GHK with a fatty acid attached |
They are related. They are not the same. What sits under one heading is a finding about that one ingredient.
What the document actually says
The review has a section on composition and impurities.
Under the heading for tripeptide-1 — the plain peptide, no copper — it says the commercial material is about 95% pure. It adds that the material often carries small amounts of mildly neurotoxic stuff. It then gives a clean-up: dissolve it in distilled water, spin it, and freeze-dry the liquid on top.
That is the 95% figure. It is about GHK.
Now the part that matters. In that same section, there is no entry at all for copper tripeptide-1. The review does not report a purity figure for GHK-Cu.
The source behind it is a 1987 chapter by Pickart and Lovejoy, in Methods in Enzymology. That work is about the peptide itself.
Then the summary says something different
A review like this ends with a summary. It is short, it is readable, and it is the part most people reach.
In that summary, the same document gives the figure to GHK-Cu²⁺ — copper tripeptide-1. In the next breath it still describes dissolving GHK.
So one document says two things. The body gives the number to the plain peptide. The summary gives it to the copper version. Both cannot be right.
We follow the body, and we say so on the site. That is where the heading and the original reference point.
But it is easy to see how the other version spread. A summary is quotable. A composition table under a subheading is not.
It is not the only mix-up in there
Once you notice the pattern, the same review has more of it.
The wrinkle trials are on something else. The human trials the review reports for appearance used palmitoyl tripeptide-1 — the fatty-acid version. They are not measurements of GHK-Cu. Nothing in them carries over to it.
Some figures cover the whole group. The "skin conditioning agent" label and the "less than 10 ppm" usage figure are given for all the ingredients together. They were not worked out for GHK-Cu on its own. The usage range comes from an industry survey across the same group.
None of this makes the review bad work. It is a careful document about a family of ingredients. The trouble starts on the way out — when a number crosses a heading and lands somewhere as a fact about one molecule.
What the human evidence on GHK-Cu actually looks like
While we were in there, it is worth noting what the review's own trial record holds for GHK-Cu itself.
There is one randomised human comparison, on skin resurfaced with a CO₂ laser. Image analysis and blinded raters found no significant difference between the GHK-Cu routine and the control routine. Not in redness. Not in wrinkles. Not in overall skin quality.
The patients' own satisfaction ratings did differ. The measured outcomes did not.
So how pure is the GHK-Cu you buy?
The honest answer is that the published literature does not say, for any particular vial.
The 95% figure describes a different molecule. The document everyone quotes carries no purity figure for commercial GHK-Cu at all. The chemistry papers do tell you other useful things. GHK-Cu is very water-loving and needs a carrier to cross skin, and it breaks down under basic and oxidising conditions. But the purity of one batch is not something a paper can tell you.
Only one document can: a certificate of analysis for that lot.
That is a dull ending for a detective story. It is also the only one the evidence supports. A purity number with no lot number attached describes an idea of a product, not a product.
How to check a number like this yourself
It generalises, and it takes about ten minutes.
- Find the document, not the quote. If nobody can point you at a source, that is the finding.
- Check which heading the sentence sits under. In a review of several related ingredients, the heading does as much work as the sentence.
- Read the summary against the body. Summaries squeeze things down, and that is where the subject of a sentence slips.
- Ask what the number could be measuring. Purity belongs to a batch. A figure with no batch attached is a claim about a category.
Sources
- Cosmetic Ingredient Review, Safety assessment of tripeptide-1, copper tripeptide-1 and palmitoyl tripeptide-1 (2014)
- Effects of topical copper tripeptide complex on CO2 laser-resurfaced skin
- Physicochemical characterization of native glycyl-L-histidyl-L-lysine tripeptide — a preformulation study for dermal delivery