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Attribute	BPC-157 The most widely used healing peptide in the world, supported by a large rodent literature and zero completed randomised human trials.	GHK-Cu Copper-binding tripeptide with forty years of topical research behind it - and essentially none behind the injectable form people are buying.	Retatrutide Triple GLP-1 / GIP / glucagon agonist producing the largest weight loss recorded in any obesity trial to date. Investigational - not approved anywhere.
Evidence	Preclinical	Preclinical	Trials
Class	Healing & repair	Skin & cosmetic	Incretin / GLP-1 class
Regulatory status	Not approved anywhere. In 2023 the FDA placed BPC-157 in Category 2 of its bulk drug substances review - substances with significant safety concerns - barring compounding pharmacies from producing it. WADA-prohibited in sport.	Widely sold as a topical cosmetic ingredient, which is a legal and well-established use. The injectable form is not approved and appears on the FDA's Category 2 bulk substances list.	Investigational. Eli Lilly's phase 3 TRIUMPH programme is ongoing and no regulator has approved retatrutide for any indication. Everything sold online is research-chemical grade.
Route	subcutaneous, oral, intramuscular	topical, subcutaneous	subcutaneous
Cadence	Daily	Daily	Once weekly
Half-life	~15 minutes (rat IV; no human PK published)	Minutes in circulation; the copper complex itself persists in tissue longer	~6 days
Reported dose	250-500 mcg	1-2 mg	1-12 mg
Goals	Injury healingGut	SkinHairInjury healingLongevity	Fat lossLongevity
Main side effects	Injection-site irritation Occasional reports of lightheadedness or fatigue after dosing No systematic human safety dataset exists - the absence of reported effects reflects absence of study, not evidence of safety	Injection-site redness, stinging and transient blue discolouration Topically: irritation, especially when layered with vitamin C or strong exfoliating acids Theoretical copper accumulation with high-dose sustained systemic use	Nausea - 14% at 1 mg rising to 60% at 12 mg in phase 2 Vomiting, diarrhoea and constipation, concentrated during dose escalation Resting heart rate up ~4-6 bpm at the top dose, peaking near week 24 then declining

The GLP class, at matched doses

The three incretins in this reference are the most frequently compared compounds on the site, and the comparison is routinely done badly - usually by putting peak numbers from trials of different lengths next to each other.

Compound	Receptors	Trial	Duration	Mean weight change	Status
Semaglutide 2.4 mg	GLP-1	STEP-1	68 wk	~-14.9%	Approved
Tirzepatide 15 mg	GLP-1 + GIP	SURMOUNT-1	72 wk	~-20.9%	Approved
Retatrutide 12 mg	GLP-1 + GIP + glucagon	Phase 2	48 wk	~-24.2%	Investigational

Read the duration column before the weight column. Retatrutide reached the largest number in the shortest time, and its phase 2 curve had not flattened at 48 weeks - which is the genuinely notable finding, more than the headline percentage.

But efficacy is not the only axis. Semaglutide is the only one of the three with a cardiovascular outcomes trial showing reduced heart attacks and strokes. Tirzepatide is approved, prescribable and comes from a verified supply chain. Retatrutide exists only as grey-market material with no long-term human safety record. The trade is mostly about certainty, not potency.