buying guide
What Does 2% GHK-Cu Mean? A Guide to Copper Peptide Concentration
"2% GHK-Cu" means that 2% of the product, by weight, is the copper peptide. In practice that's 2 grams in every 100 grams of serum, or about 20 mg in every millilitre. It tells you how much of the peptide went into the formula. It doesn't tell you how much reaches your skin intact, and it isn't proof that 2% works better than 1%.
Below: how to read the number and convert it, why it's so much higher than the amount in your blood, where the research on concentration stops, and what else to check before you let a percentage decide for you.
What 2% GHK-Cu actually means
A percentage on a skincare label is almost always by weight. So "2% GHK-Cu" means GHK-Cu, listed on the ingredient list as copper tripeptide-1, makes up 2% of everything in the bottle. The other 98% is water, hydrators, thickeners, preservatives and any other actives. Chemists call that the vehicle.
The same number can be written a few ways, which is where confusion creeps in:
| Percentage | Parts per million (ppm) | Per millilitre (roughly) | In a 30 ml bottle | In a 45 ml bottle |
|---|---|---|---|---|
| 0.5% | 5,000 ppm | 5 mg | 150 mg | 225 mg |
| 1% | 10,000 ppm | 10 mg | 300 mg | 450 mg |
| 2% | 20,000 ppm | 20 mg | 600 mg | 900 mg |
The per-millilitre figures assume the serum weighs about the same as water, which is close enough for comparing bottles. If a brand quotes ppm, divide by 10,000 to get the percentage. If it quotes milligrams without saying per how many millilitres, it hasn't given you a concentration at all.
Why the number on the bottle is so much higher than in your body
Your body makes GHK on its own. According to a 2018 review in the International Journal of Molecular Sciences, blood levels sit around 200 ng/mL at age 20 and fall to about 80 ng/mL by 60. That's a tiny amount: 200 ng/mL works out to about 0.00002%.
So why put 2% in a serum, which is roughly 100,000 times more? Because a serum has to get through the top layer of skin first, and that layer is built to keep things out. Copper peptides are small, and a 2018 review in the journal Cosmetics notes that some are able to get through it. Only part of what you apply makes it in. The number on the bottle is what goes on, not what arrives.
Where the research on concentration stops
Here's the honest part. Most of the lab work on GHK-Cu was done on cells in a dish, where the peptide bathes the cells directly and tiny amounts are enough. Those amounts are measured in completely different units from a percentage on a serum, and they can't be converted into "the right percentage for your face".
The human studies are fewer. The most cited one followed 71 women using a GHK-Cu facial cream for 12 weeks, and the same 2018 review reports their skin measured denser and thicker, with shallower fine lines. That study tested one formula at its own concentration. It didn't compare concentrations.
We haven't found a published study that tests, say, 1% against 2% against 5% on skin and names a best number. So any brand claiming its percentage is the proven optimum is claiming more than the research shows. That includes us, which is why we don't.
Why more isn't automatically better
It's tempting to treat a percentage like a volume knob. Copper peptides don't work that way, for three reasons:
- It's a signal, not a filler. GHK-Cu nudges the cells that make collagen to do their job. It doesn't physically fill anything in. Signals tend to level off: past a point, more doesn't mean louder.
- Stability gets harder. The copper has to stay attached to the peptide for it to work. The formula around it has to keep it that way for the life of the bottle, whatever the percentage.
- Tolerance matters. A serum you can use every day without stinging will do more than a stronger one you give up on after a week.
So a higher number on the label isn't a bad sign. It just isn't, on its own, a better one.
What a 2% GHK-Cu label doesn't guarantee
A stated percentage tells you what went into the batch. It can't tell you:
- Whether the copper is still attached. Heat, light, strong acids and ingredients that grab metals, such as EDTA, can pull it off. The colour is your quick check: blue is intact, green or colourless is a warning. See how to spot oxidised or low-quality GHK-Cu.
- How it's been stored. A bottle that spent a summer in a hot warehouse isn't the bottle that left the lab. Our guide to GHK-Cu shelf life covers storage.
- Whether it suits your skin. Two serums at 2% can feel completely different because the rest of the formula is different.
Two products that both say 2% can perform differently. The percentage lets you compare them fairly. The rest of the label, and your skin, decides between them. Our guide to choosing a copper peptide serum covers the other checks.
How to use a percentage when you're shopping
- Check that the percentage is for GHK-Cu itself, not for a blend of several peptides.
- Convert it using the table above, so you can compare bottles of different sizes.
- Work out the cost per milligram if price matters. Our piece on what you give up with a cheap copper peptide serum shows how.
- Then check the rest: blue colour, no EDTA, protective packaging, a texture you'll use.
Where koppā lands, and why we print it
The serum is 2% GHK-Cu: 20,000 ppm, or 900 mg in the 45 ml bottle. The capsule cream and the balm stick are 0.5% each. They do different jobs. The serum is the step that carries the most peptide, the cream adds moisture on top, and the balm is for spots that need extra. We print every number because most brands don't, and a number is the only way you can compare. We don't claim 2% is the proven best, because nobody has shown that.
Frequently asked questions
Is 2% GHK-Cu a high concentration?
It's far above the amount in your blood, which is normal for anything applied to skin, because only part of it gets through the top layer. Compared with other products, it's hard to say, because most brands don't disclose a percentage at all. Either way, a higher percentage isn't proven to work better on skin.
Is 1% or 2% GHK-Cu better?
Nobody has published a study comparing them head to head on skin, so there's no proven answer. A well-made 1% serum that keeps the copper attached may do more than a poorly made 2% one. Use the percentage to compare fairly, then judge the formula, the packaging and how your skin takes it.
What does ppm mean on a copper peptide label?
Parts per million. It's another way of writing a concentration: divide by 10,000 to get the percentage. So 20,000 ppm is 2%, and 10,000 ppm is 1%. It's the same fact in bigger digits. If you're comparing bottles, convert everything to percentages first.
The short version
2% GHK-Cu means 2% of the product by weight is copper peptide, about 20 mg in every millilitre. It's a useful number because it lets you compare products, and a missing number is worth asking about. It isn't proof of results: nobody has shown 2% beats 1% on skin, and the formula, the colour and the storage matter as much as the digit. For the basics of the peptide itself, start with what GHK-Cu is.
