Comparison
GHK-Cu vs Vitamin D3 + K2
Side-by-side of GHK-Cu and Vitamin D3 + K2. 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.
Vitamin D3 + K2
Vitamin D3 K2 supplement profile: cholecalciferol at 1000-4000 IU/day corrects deficiency, MK-7 directs calcium to bone, away from arteries.
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
Vitamin D3 + K2
- •Reduces non-vertebral fractures 10-20% in older adults at 800 IU/day or above when combined with calcium
- •VITAL trial showed neutral results on primary CV and cancer endpoints at 2000 IU/day over 5 years
- •Vitamin D supplementation reduces respiratory infection incidence ~10-20% in deficient populations
- •K2 MK-7 has 72-hour plasma half-life vs 1-2 hours for MK-4; once-daily dosing is sufficient
- •Synergy hypothesis is largely preclinical; dedicated combination RCTs are limited
- •Daily dosing outperforms bolus dosing for immune and infection outcomes
Side-by-side
| Attribute | GHK-Cu | Vitamin D3 + K2 |
|---|---|---|
| Category | peptide | supplement |
| Also known as | Copper Peptide, Glycyl-L-histidyl-L-lysine copper, GHK | cholecalciferol + menaquinone, D3/K2, vitamin D3 with MK-7 |
| Half-life (hr) ↗ | 0.5 | 360 |
| Typical dose (mg) ↗ | 2 | 0.05 |
| Dosing frequency | daily | daily with a fat-containing meal |
| Routes | topical, subcutaneous | oral |
| Onset (hr) | 24 | 24 |
| Peak (hr) | 168 | 168 |
| Molecular weight | 340.85 | 384.64 |
| Molecular formula | C14H24N6O4 (GHK alone); C14H22CuN6O4 with Cu(II) | C27H44O (D3); C46H64O2 (MK-7) |
| 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. | D3 converts to calcidiol then calcitriol, activating the vitamin D receptor (VDR) to increase intestinal calcium absorption and modulate immune and bone gene transcription. K2 carboxylates osteocalcin and matrix Gla protein, directing calcium toward bone and inhibiting vascular calcification. |
| Legal status | Topical cosmetics legal in most jurisdictions; injectable form not FDA approved for any indication; research-use-only grey market | Dietary supplement (global) |
| WADA status | allowed | allowed |
| DEA / Rx | Topical OTC (cosmetic); injectable not FDA approved; research-chemical status | Not scheduled |
| Pregnancy | Insufficient data; topical use likely low-risk; injectable not recommended | Recommended at standard doses for fetal bone development; consult clinician at higher doses |
| CAS | 49557-75-7 | 67-97-0 |
| PubChem CID | 73587 | 5280795 |
| Wikidata | Q3104638 | Q139347 |
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)
Vitamin D3 + K2
Common side effects
- GI upset at high doses
- headache (rare)
- hypercalcemia (only at sustained very high D3 doses)
Contraindications
- hypercalcemia
- sarcoidosis
- active hyperparathyroidism
- warfarin therapy (K2 component requires stable intake)
Interactions
- warfarin: K2 component can affect anticoagulation; maintain stable intake and inform anticoagulation clinic(moderate)
- thiazide diuretics: additive calcium retention; hypercalcemia risk with high-dose D3(moderate)
- digoxin and calcium channel blockers: additive effects from D3-induced hypercalcemia(moderate)
- glucocorticoids: reduced vitamin D efficacy and bone effects(moderate)
- cholestyramine and orlistat: bind fat-soluble vitamins; separate dosing by 2 to 4 hours(moderate)
Which Should You Take?
Vitamin D3 + K2 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 bone density, pick Vitamin D3 + K2.
- → If your priority is cardiovascular health, pick Vitamin D3 + K2.
Edge case: If you want to avoid research-only / gray-market sourcing, Vitamin D3 + K2 is the more accessible choice.
Default choice: Vitamin D3 + K2. 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 Vitamin D3 + K2?
GHK-Cu and Vitamin D3 + K2 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 Vitamin D3 + K2?
GHK-Cu half-life is 0.5 hours; Vitamin D3 + K2 half-life is 360 hours.
Can you stack GHK-Cu with Vitamin D3 + K2?
Stack compatibility depends on mechanism overlap, legal status, and individual response. Check each compound page for specific interactions and contraindications before combining.
Go deeper