GHK (Glycyl-Histidyl-Lysine) is a peptide the human body produces naturally, found in plasma, saliva, and urine, and its concentration declines significantly with age. AHK (Alanyl-Histidyl-Lysine) is a synthetic compound that does not occur naturally in the body, developed as a synthetic analogue of GHK. The substitution of glycine (G) for alanine (A) in the first position changes the compound's interaction characteristics, which may underlie its more hair-focused research profile relative to GHK-Cu.

GHK-Cu is one of the most extensively characterised cosmetic peptide systems. Collagen synthesis, elastin production, wound healing, anti-inflammatory signalling, antioxidant support, gene expression modulation: all have been studied in its context across decades of published work. It is a generalist compound with a broad, well-documented research base.

AHK-Cu's research base is smaller but more focused. The studies that exist concentrate specifically on follicular tissue: keratinocyte proliferation, follicle survival, and hair-cycle activity. It is a compound that has been investigated for a narrower set of questions; harder to draw broad conclusions from, but more directly relevant if hair is the primary concern.

GHK-Cu's scalp relevance comes primarily through its broader mechanisms. VEGF upregulation supports perifollicular vascularity; anti-inflammatory activity addresses the chronic low-grade scalp inflammation associated with androgenetic alopecia; tissue remodelling properties extend to the scalp as much as to facial skin. GHK-Cu is a compound with genuine scalp relevance by virtue of its broader biology, and should not be dismissed as a hair loss ingredient simply because it was not investigated in that context specifically.

AHK-Cu's scalp relevance is more direct in terms of research focus. Studies have investigated its effects specifically on follicular tissue and hair-cycle promotion. Whether this makes it categorically more effective for hair loss applications is not established by human trial evidence; it does make it the compound that has been explored with that question more explicitly in mind.

If you're using a copper peptide primarily for facial skin: texture, firmness, fine lines, post-procedure recovery, or general skin remodelling, GHK-Cu is the better-evidenced choice. The research supporting collagen synthesis, anti-inflammatory activity, and wound-healing mechanisms in skin is substantially more developed for GHK-Cu than for AHK-Cu. It can also be applied to the scalp, where its vascular and anti-inflammatory properties are genuinely relevant to hair health.

If androgenetic alopecia, diffuse thinning, or scalp health is your primary focus, AHK-Cu is the more hair-focused option. The research that exists for it has been conducted specifically in scalp and follicle contexts, which makes it the compound explored with that application more explicitly in mind. The same caveat applies as with any topical hair loss ingredient: the evidence remains largely in vitro and in organ culture models, and clinical human trials have not been published.

The two compounds are not redundant. Their mechanisms overlap in some areas and diverge in others, and they are intended for different application areas: GHK-Cu on the face and skin, AHK-Cu on the scalp. Using both simultaneously on their respective areas is straightforward; there is no known interaction between them at the topical level, and the shared carrier formulation means the application experience is consistent across both.

Many users in the research community who are managing both skin ageing and hair loss use GHK-Cu and AHK-Cu as complementary parts of a broader protocol, sometimes alongside 2dDR for its distinct vascular mechanism.

Can I use GHK-Cu and AHK-Cu at the same time?

Yes. They are intended for different application areas: GHK-Cu for the face and skin, AHK-Cu for the scalp. Using both simultaneously presents no practical issue, and no interaction between the two compounds has been reported in the published literature. Many users apply AHK-Cu to the scalp and GHK-Cu to the face as part of the same routine.

Why is AHK-Cu more expensive than GHK-Cu?

Raw material cost. AHK-Cu is a synthetic compound produced in smaller quantities by fewer suppliers than GHK-Cu, which has been manufactured at scale for decades. The price difference reflects the supply chain rather than the formulation quality; both serums are produced in the same carrier to the same purity standard.

Can I use GHK-Cu on my scalp instead of AHK-Cu?

GHK-Cu can be applied to the scalp and has relevant activity there via its vascular and anti-inflammatory mechanisms. However, AmpleLab's 1% GHK-Cu serum is formulated and dosed for facial application at 0.15ml daily. For scalp-focused use, AHK-Cu (1%) is the more hair-focused option, dosed at 0.25ml daily for scalp coverage.

Is one compound stronger than the other?

Not in a meaningful sense. They have different research profiles rather than different potency levels. GHK-Cu has more research behind it overall; AHK-Cu has been investigated more specifically in hair and scalp contexts. Neither has been compared to the other directly in a controlled human trial, so the question of which is stronger doesn't map cleanly onto the available evidence.

Where can I find the full explainer articles for each?

AmpleLab has a dedicated article for each compound covering the science, formulation rationale, and product details in full. See GHK-Cu: The Copper Peptide That Started It All and the dedicated AHK-Cu article in the Research and Notes section.

Should I add 2dDR to a copper peptide protocol?

2dDR acts through a distinct vascular mechanism, upregulating VEGF via a different pathway to the copper peptides. The mechanisms are distinct and may be complementary, particularly for scalp applications where perifollicular vascularity is a relevant target. AmpleLab's 2% 2dDR Hair Serum is covered separately in the Research and Notes section.