What did @sarah.brock46 actually say?
The claim is specific: GHK-Cu "will destroy the rest of the peptides" if taken at the same time, and you need a 30-minute separation window to get "maximum benefit." She frames this as practical advice, not speculation, and offers a shower-based timing hack to make it workable. It sounds authoritative. The problem is that the core biochemical explanation she gives does not hold up well under scrutiny.
She attributes the interference to molecular size, saying the GHK-Cu molecule is "really big" and that bigness is somehow destructive to other peptides. This is where things start to go sideways. GHK-Cu is actually a tripeptide, meaning it contains exactly three amino acids. In peptide terms, that is quite small, not large.
Does the science back this up?
No peer-reviewed evidence supports the idea that GHK-Cu degrades or denatures co-administered peptides in vivo because of its molecular size. GHK-Cu is a tripeptide with a molecular weight of roughly 340 daltons in its free acid form. Compare that to something like BPC-157, which has 15 amino acids, or CJC-1295, which has 30. If molecular bulk were the issue, GHK-Cu would be among the least likely offenders.
What GHK-Cu does have is a strong affinity for copper ions, which gives it real biochemical activity. Research by Pickart and Margolina (2018, Symmetry) documents its role in wound healing, anti-inflammatory signaling, and tissue remodeling. But that copper-binding activity is not the same as peptide degradation. There is no published pharmacokinetic data showing that subcutaneous or intranasal co-administration of GHK-Cu meaningfully degrades other peptides in the injection site or bloodstream.
What did they get wrong (or right)?
The "destroy" framing is wrong, and the molecular size explanation is backwards. GHK-Cu is one of the smaller peptides in common use. Saying it is "really big" and therefore destructive misrepresents basic peptide chemistry and will confuse people who are trying to understand what they are putting in their bodies.
That said, the general instinct to space out peptide administrations is not crazy. Copper ions can influence the stability of certain peptides in solution, and there are legitimate reasons to avoid mixing peptides in the same syringe without knowing their compatibility. Some practitioners do recommend separating GHK-Cu from other peptides, though the reasoning is usually about copper ion reactivity in solution, not in vivo destruction after injection.
The shower timing hack is harmless and actually a reasonable way to build a consistent routine. Getting credit where it is due: adherence matters, and a simple behavioral anchor is a practical suggestion. But practical delivery does not redeem a flawed mechanism claim.
What should you actually know?
If you are using peptides under medical supervision, the question of timing and compatibility is worth asking your prescribing clinician, not sourcing from a TikTok video with no citations. Here is what the actual literature suggests.
GHK-Cu's activity is largely tied to its copper-chelating properties, which affect pathways including superoxide dismutase activity and TGF-beta signaling (Pickart et al., 2012, Journal of Aging Research). Copper ions in high concentrations can theoretically oxidize certain amino acid residues in other peptides, but this is a concern in compounding and storage, not typically a concern after administration when peptides are diluted in systemic circulation.
- Mixing peptides in the same vial before injection raises real stability questions that a compounding pharmacist should evaluate.
- Injecting them separately at different sites or times avoids any theoretical in-solution interaction.
- A 30-minute window is not an evidence-based interval. It is a round number with no published pharmacokinetic justification.
- If you are using any peptide therapy, it should be prescribed and monitored by a licensed clinician familiar with your health history.