Comparison
GHK-Cu vs L-Theanine
Side-by-side of GHK-Cu and L-Theanine. Every row below is pulled from the compound schema and will update as our data grows. For deeper reads, follow through to each compound page.
GHK-Cu
GHK-Cu peptide (glycyl-L-histidyl-L-lysine copper) is a topical copper peptide. Trials show fine-line and wound-healing gains; injectable longevity claims rem.
L-Theanine
L-theanine is a non-protein amino acid found in tea leaves. The most-replicated nootropic; pairs with caffeine at 1:1 (100-200 mg each) for acute focus.
Effects at a glance
GHK-Cu
- •Endogenous tripeptide that binds copper(II); plasma levels decline ~60% from age 20 to 60
- •Topical RCTs show improvement in skin firmness, fine lines, and barrier function over 12 weeks
- •Wound-healing models report accelerated re-epithelialization in diabetic and aged skin
- •Pickart gene-expression analyses show reset of >4000 genes toward a younger expression profile in cell culture
- •Anecdotal subcutaneous longevity protocols use 1 to 3 mg daily; no human longevity RCTs exist
- •Hair-growth claims rest on small open-label trials and topical scalp formulations
L-Theanine
- •Non-protein amino acid in tea; the most-replicated nootropic in the human RCT literature
- •Caffeine + theanine at 1:1 (100-200 mg each) is the gold-standard acute focus stack
- •Solo doses of 200-400 mg reduce subjective stress and improve sleep quality
- •Increases alpha-wave EEG activity within 30-45 minutes of 200 mg oral dose
- •Crosses blood-brain barrier; bioavailability high, half-life 60-90 minutes
- •Clean safety record; minimal interactions at supplement doses
Side-by-side
| Attribute | GHK-Cu | L-Theanine |
|---|---|---|
| Category | peptide | supplement |
| Also known as | Copper Peptide, Glycyl-L-histidyl-L-lysine copper, GHK | theanine, gamma-glutamylethylamide |
| Half-life (hr) ↗ | 0.5 | 1.5 |
| Typical dose (mg) ↗ | 2 | 200 |
| Dosing frequency | daily | as needed (with caffeine) or daily |
| Routes | topical, subcutaneous | oral |
| Onset (hr) | 24 | 0.5 |
| Peak (hr) | 168 | 1 |
| Molecular weight | 340.85 | 174.2 |
| Molecular formula | C14H24N6O4 (GHK alone); C14H22CuN6O4 with Cu(II) | C7H14N2O3 |
| Mechanism | Tripeptide that chelates Cu(II) and delivers it to copper-dependent enzymes (lysyl oxidase, superoxide dismutase). Modulates expression of >4000 genes toward a younger profile in fibroblast culture, including upregulation of decorin and downregulation of pro-inflammatory cytokines. | Crosses BBB; modulates GABA/dopamine/serotonin (modest); increases alpha-wave EEG activity; dampens stress-induced sympathetic response without sedation. |
| Legal status | Topical cosmetics legal in most jurisdictions; injectable form not FDA approved for any indication; research-use-only grey market | OTC dietary supplement |
| WADA status | allowed | allowed |
| DEA / Rx | Topical OTC (cosmetic); injectable not FDA approved; research-chemical status | OTC supplement |
| Pregnancy | Insufficient data; topical use likely low-risk; injectable not recommended | Insufficient supplement-dose data; tea-source intake safe |
| CAS | 49557-75-7 | 3081-61-6 |
| PubChem CID | 73587 | 439378 |
| Wikidata | Q3104638 | Q909931 |
Safety profile
GHK-Cu
Common side effects
- mild erythema at topical site
- transient itch
- blue-green discoloration of injection site (copper)
- rare contact dermatitis
Contraindications
- copper allergy
- Wilson disease
- open wound near injection site (caution)
- pregnancy (no data)
Interactions
- topical retinoids: additive irritation; alternate days or apply at different times(minor)
- topical vitamin C (ascorbic acid): ascorbate reduces Cu(II) to Cu(I), which can destabilize the GHK-Cu complex; separate by 30 minutes(minor)
L-Theanine
Common side effects
- mild GI upset (rare)
- headache (rare)
Contraindications
- pregnancy / lactation (insufficient data at supplement doses)
- concurrent strong GABAergics without caution
Interactions
- caffeine: synergistic for acute focus; dampens jitter without blunting alertness(minor)
- benzodiazepines / alcohol: potential additive sedation(minor)
Which Should You Take?
L-Theanine comes out ahead for most readers on the criteria we weight: 3 catalogued goals, OTC dietary supplement, oral dosing, with a Tier-A outcome catalogued. GHK-Cu is the right call when one of the conditionals below applies.
- → If your priority is skin health, pick GHK-Cu.
- → If your priority is wound healing, pick GHK-Cu.
- → If your priority is focus or working memory, pick L-Theanine.
- → If your priority is stress and HPA-axis regulation, pick L-Theanine.
Edge case: If you want to avoid research-only / gray-market sourcing, L-Theanine is the more accessible choice.
Default choice: L-Theanine. Lower friction to source, a Tier-A evidence outcome catalogued, and broader goal coverage. Reach for GHK-Cu only if your priority sits squarely in the goals it owns above.
This verdict is generated from each compound's schema (goals, legal status, evidence outcomes, dosing route). It updates automatically as our compound data evolves; the deeper read sits on each individual compound page.
Common questions
What is the difference between GHK-Cu and L-Theanine?
GHK-Cu and L-Theanine differ in category (peptide vs supplement), mechanism, and typical dosing. See the side-by-side table for full details.
Which has a longer half-life, GHK-Cu or L-Theanine?
GHK-Cu half-life is 0.5 hours; L-Theanine half-life is 1.5 hours.
Can you stack GHK-Cu with L-Theanine?
Stack compatibility depends on mechanism overlap, legal status, and individual response. Check each compound page for specific interactions and contraindications before combining.
Go deeper