GHK-Cu Reconstitution — Volume and Concentration Reference

Published 2026-10-02 · Lyophile Editorial

Copper peptide work has one quirk that separates it from every other reconstitution: the copper itself. GHK-Cu is a tripeptide — glycyl-L-histidyl-L-lysine — with a Cu(II) ion chelated to the histidine imidazole nitrogen and the amine terminus. That complex is what gives the powder its deep blue color, and the color is your fastest visual check on degradation. What follows is volume math and handling notes only. Research use only, not clinical guidance.

GHK-Cu reconstitution calculator

Three variables drive everything: mass of peptide in the vial, volume of diluent you add, and the syringe you draw with.

| Input | Typical value | What it controls | |---|---|---| | Vial mass | 50 mg | Total peptide-complex in the vial | | Diluent volume | 5 mL | Concentration denominator | | Syringe | U-100 insulin | 1 unit = 0.01 mL | | Result | 10,000 mcg/mL | 100 mcg per unit |

One wrinkle specific to GHK-Cu: the mass on the label may be the copper-peptide complex, not the free peptide. A 50 mg vial of "GHK-Cu" holds 50 mg of the complex, and copper accounts for roughly 10–12% of that mass depending on hydration state. When a certificate of analysis reports "peptide content" separately from "complex mass," use whichever number matches what you actually weighed into the vial.

How much bacteriostatic water for a 50 mg GHK-Cu vial?

50 mg GHK-Cu in 5 mL bacteriostatic water gives 10,000 mcg/mL, or 100 mcg per unit on a U-100 insulin syringe.

The math: 50 mg × 1000 = 50,000 mcg. Divide by 5 mL for 10,000 mcg/mL. Divide by 100 units/mL for 100 mcg/unit. Bacteriostatic water per USP <797> contains 0.9% benzyl alcohol as a preservative.

Step by step:

1. Swab the vial stopper and the diluent septum with 70% isopropyl alcohol. Let both air-dry. Alcohol carried into the vial is a real contaminant.
2. Draw 5 mL of bacteriostatic water into a 5 mL or 10 mL syringe. Vent the peptide vial with a second needle if you're adding more than ~2 mL, or headspace pressure will fight you.
3. Aim the diluent stream at the glass wall, not the powder cake. GHK-Cu dissolves readily, but a direct jet can shear and foam the solution.
4. Swirl. Do not vortex or shake. The copper complex isn't fragile in the covalent sense, but mechanical stress and foaming drive surface denaturation and a visible color shift.
5. Let it sit 5–10 minutes. A properly reconstituted GHK-Cu solution is clear, deep blue, no particulate. Cloudiness or a green-brown cast is a red flag.

Reconstitution math for other vial sizes

Concentration in mcg/mL = (vial mg × 1000) ÷ diluent mL. Concentration per U-100 unit = that result ÷ 100.

| Vial | Diluent | mcg/mL | mcg per U-100 unit | |---|---|---|---| | 10 mg | 2 mL | 5,000 | 50 | | 20 mg | 2 mL | 10,000 | 100 | | 50 mg | 5 mL | 10,000 | 100 | | 50 mg | 10 mL | 5,000 | 50 | | 100 mg | 10 mL | 10,000 | 100 |

20 mg in 2 mL and 50 mg in 5 mL land on the same 100 mcg/unit. Pick the ratio, not the vial size. For 50 mcg/unit, double the diluent volume relative to the table.

Does GHK-Cu need a different diluent than other peptides?

Bacteriostatic water works. The copper complex, though, is sensitive to pH and chelating agents in ways most peptides are not. Copper binds strongly to EDTA, citrate, and phosphate buffers. Add any of those and you can strip the Cu(II) out of the peptide, turning the blue solution pale or colorless. Use plain bacteriostatic water or 0.9% saline. Avoid Tris and phosphate-buffered diluents unless the supplier's published specification explicitly says the complex tolerates them.

Two handling notes specific to copper peptides:

• Light. The Cu(II)-peptide complex absorbs strongly in the visible range and is photolabile over time. Store reconstituted solution in amber glass or wrapped in foil. A clear vial left on a bench under fluorescent light for a week is a different material than one kept dark.
• Oxidation state. Cu(II) is the stable form in the complex. Reducing agents — ascorbate, DTT, beta-mercaptoethanol — will reduce the copper and break the blue color. Keep them out of the same tube.

Common failure modes

Cold vial, immediate draw. Add diluent to a cold vial and draw right away, and you'll leave undissolved material at the bottom that reads as haze — cold solution, cold glass, hygroscopic powder cake. Bring the vial to room temperature first, then reconstitute.

Assuming the label mass is free peptide. A COA reporting 50 mg complex at 88% peptide content means actual GHK-Cu is ~44 mg. Use whichever number you're tracking, and know which one it is before you calculate.

Reusing a needle to vent and draw. The vent needle picks up aerosolized powder on the way out. Use a fresh draw needle.

Storage after reconstitution

Reconstituted GHK-Cu in bacteriostatic water is generally held at 2–8 °C, protected from light, per the supplier's published stability specification. Check that document — stability claims vary by manufacturer and by whether the solution is the complex or the free peptide. Benzyl alcohol at 0.9% suppresses bacterial growth but does not stop hydrolysis or photodegradation. Freeze-thaw cycles are hard on the complex. Aliquot if you're storing longer than the supplier's stated window.

Where to source bacteriostatic water

• BAC Water Depot — 0.9% benzyl alcohol, USP-grade, multiple vial sizes
• Med Lab Supply — sterile-filtered, individually sealed vials
• Eli Lilly (via distributors) — the reference bacteriostatic water product

Where to source research peptides

• Alpha Amino USA — per-lot HPLC/MS COA, US-shipped
• Peptide Sciences — published COAs with peptide content and copper-complex mass
• Bachem — research-grade catalog peptides with full analytical documentation

For research use only — not clinical guidance. Verify every number against your own supplier's certificate of analysis before you calculate.