Homemade topical GHK-Cu — someone check my concentration math

P
Joined 2026
50 posts
3/7/2026 · 1824 views

Making my own 2% serum and I keep getting tangled up on ppm vs mg/mL vs percent. Want to double check before I waste a vial.

Starting material: 50mg lyophilized GHK-Cu vial. I want to make 30mL of 2% serum.

2% by mass in a water-based vehicle ≈ 20mg/mL ≈ 20,000 ppm. So 30mL * 20mg/mL = 600mg needed. That's way more than one 50mg vial. Which means one vial at 30mL is closer to 1.67mg/mL = 0.167%.

Questions:

  1. Is 'percent' in cosmetic chem w/v (mass per volume) or w/w (mass per mass)? I've been assuming w/v.
  2. For a legitimate 2% serum I'd need 600mg per 30mL bottle, which is a lot of peptide. The commercial stuff can't actually be 2% GHK-Cu at their price points — am I misreading labels?
  3. What's a realistic DIY concentration that's worth the trouble? I'm seeing 0.05–0.2% in published topical studies, so maybe I'm overshooting.

Vehicle plan: preserved hydrosol base with a little glycerin, pH buffered to ~5.5. Skipping anything that'll reduce the copper.

12 Replies

T
Joined 2025
58 posts
theoreticRegular
3/7/2026

The published topical literature is mostly in the 0.05–0.2% range. You don't need 2% and there's decent evidence returns are flat or declining above ~0.5%. One 50mg vial in 30mL gives you 0.17%, which is right in the sweet spot.

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H
Joined 2025
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hexaclinicContributor
3/8/2026

Your math is right. Cosmetic percent is almost always w/w, but for dilute aqueous serums w/v and w/w are within rounding error. The real issue is what you identified — commercial '2% GHK-Cu' serums almost certainly aren't. Read the INCI list: if GHK-Cu isn't in the top 5 ingredients, it's not 2% of anything.

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P
Joined 2026
46 posts
3/8/2026

For DIY I run 0.1% and it's been fine on my skin for 6 months. One 100mg vial makes 100mL at that strength which lasts forever. 2% is marketing math, not working math.

C
Joined 2025
46 posts
3/8/2026

Good post — this is the kind of 'check my work' we want more of. Tagging for any cosmetic chem folks lurking.

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D
Joined 2025
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dr_doubtRegular
3/9/2026

@petal_push short answer: no. Cosmetic actives are notoriously under-verified. Assume the label is aspirational.

P
Joined 2026
32 posts
3/10/2026

If 0.1–0.2% is the real working range, the commercial serums charging $90 for 30mL of '2%' are either lying or using way less peptide than labeled. Is there any independent testing?

P
Joined 2026
50 posts
3/10/2026

@bac_water_noob good catch — I was going to use citric. What's a better option?

B
Joined 2026
22 posts
3/10/2026

pH 5.5 buffered how? Citric? That'll chelate the copper off the peptide.

H
Joined 2025
205 posts
hexaclinicContributor
3/10/2026

Lactic acid works, or a phosphate buffer. Avoid anything with strong chelation properties (citric, EDTA, ascorbic). The copper is the whole point.

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S
Joined 2025
94 posts
3/12/2026

Saving this thread. Been meaning to DIY and the chelation issue is exactly the kind of thing I would have missed.

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N
Joined 2026
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notes_takerNew Member
3/15/2026

Bookmarked. Thanks for showing the work.

K
Joined 2025
12 posts
3/17/2026

Worth stating out loud: 'percent' in bodybuilding peptide talk and 'percent' in cosmetic chem mean different things. Posting this math helps new people not assume the higher number is the effective one.

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