Head to head
Retatrutide vs Ozempic: 24% vs 15% Fat Loss
Side-by-side comparison of Retatrutide (a triple-agonist research peptide) and Ozempic / Wegovy (FDA-approved single-agonist semaglutide brands). Phase 2 trial data for retatrutide compared with Phase 3 trial data for semaglutide. These are different trials, not a head-to-head study.
Verdict in 4 lines
- Trial peak weight loss: Retatrutide -24.2% at 12mg/wk (Phase 2, 48 weeks) vs Semaglutide (Wegovy) -14.9% at 2.4mg/wk (Phase 3, 68 weeks).
- FDA status: Wegovy and Ozempic are FDA-approved. Retatrutide is a research compound, Phase 3 ongoing.
- Cost via Peptara: Retatrutide about $75 to $451 per month depending on dose. Semaglutide brand retail US: about $968 to $1,349 per month.
- Different trials, different durations, different cohorts. Compare data, then decide with a licensed physician.
TL;DR comparison
One table, every row that matters. Retatrutide dose values use units from a U-100 insulin syringe with the Peptara standard reconstitution (20mg vial in 2mL bac water, 200 units per vial, 0.1mg per unit). Semaglutide dose values are the brand pre-filled pen ladder (no reconstitution required). See the reconstitution guide for the retatrutide math.
Mechanism: triple agonist vs single GLP-1
Both peptides activate gut and pancreatic hormone receptors that regulate appetite, insulin secretion, and energy expenditure. The difference is how many receptors each one activates.
Retatrutide (triple agonist)
Simultaneously activates the GLP-1 receptor (slows gastric emptying, reduces appetite), the GIP receptor (improves insulin sensitivity and fat metabolism), and the glucagon receptor (increases resting energy expenditure). The glucagon arm is the differentiator from tirzepatide and from semaglutide. More receptors activated, larger Phase 2 weight-loss signal.
View Retatrutide product
Semaglutide (single GLP-1 agonist)
A GLP-1 analog that activates only the GLP-1 receptor. Reduces appetite, slows gastric emptying, and lowers blood glucose. Sold under brand names Ozempic and Wegovy as pre-filled FlexTouch pens. Well-characterized over years of clinical use including the cardiovascular outcome trials SUSTAIN and SELECT.
Honest trade-off: more receptor activation drives a stronger fat-loss signal in trials, but also more potential for receptor-specific side effects at peak doses. For the GLP-1 + GIP (dual agonist) middle option, see Retatrutide vs Tirzepatide.
Clinical trial results
Headline figures, trial citations, and the disclaimer that has to come with them.
Retatrutide Phase 2
- Reference: Jastreboff et al, NEJM 2023
- Phase: 2
- n: 338
- Duration: 48 weeks
- 12mg/wk: -24.2% mean body weight
- 8mg/wk: -22.8% · 4mg/wk: -17.5% · 1mg/wk: -8.7% · Placebo: -2.1%
Semaglutide Phase 3 (STEP-1)
- Reference: Wilding et al, NEJM 2021
- Phase: 3
- n: 1,961
- Duration: 68 weeks
- 2.4mg/wk: -14.9% mean body weight
- Placebo: -2.4%. Trial supported the 2021 Wegovy FDA approval.
Read this before quoting either number
Phase 2 retatrutide data and Phase 3 semaglutide data come from separate studies with different durations (48 weeks vs 68 weeks), different participant pools, different sponsors, and different endpoints. These are different trials, not head-to-head numbers. The roughly 9 percentage-point gap is a Phase 2 vs Phase 3 comparison of trial peak doses, not a controlled experiment. The Phase 3 retatrutide TRIUMPH program is ongoing as of 2026 and may report different numbers than Phase 2.
FDA and regulatory status
The single most important asymmetry between these two compounds. Read this before comparing weight-loss numbers.
Semaglutide brands
Ozempic was FDA-approved in December 2017 for type 2 diabetes (maximum 2mg/wk). Wegovy was FDA-approved in June 2021 for chronic weight management in adults with BMI of 30 or higher, or 27 or higher with at least one weight-related comorbidity (maximum 2.4mg/wk). Both available via prescription from a licensed physician. Both regulated as pharmaceutical drugs in jurisdictions that follow FDA standards.
Retatrutide
Not FDA-approved as of 2026. In Phase 3 clinical trials under the Eli Lilly TRIUMPH program. Currently sold internationally only as a research compound. Peptara stocks Retatrutide and ships with a Certificate of Analysis, but it is not approved for human consumption in any jurisdiction. Researchers must follow local regulations.
Regulatory asymmetry
Semaglutide and retatrutide occupy fundamentally different regulatory positions. Semaglutide is FDA-approved with years of post-marketing safety data. Retatrutide is a research compound with Phase 3 trials still in progress. Any comparison of weight-loss outcomes must be read with that asymmetry in mind.
Side effects
Both share the GI-dominant GLP-1 class profile. Notes below are not exhaustive.
Shared (GLP-1 class)
- Nausea, most pronounced during titration
- Diarrhea
- Constipation
- Vomiting at higher doses
- Decreased appetite (intended effect)
Semaglutide-specific
- Years of clinical safety data (SUSTAIN, SELECT)
- FDA black-box warning: thyroid C-cell tumors (rodent data)
- Rare pancreatitis and gallbladder events
- Nausea typically reduces over weeks of titration
Retatrutide-specific
- Phase 2 GI rate scales with dose (roughly 30% at 12mg vs 15% placebo)
- Long-term safety still being established in Phase 3
- Triple-agonist activation can amplify early-week nausea
- Research compound: less post-marketing surveillance data
Mitigation for both: titrate slowly from the lowest starting dose, inject at the same time each week to stabilize blood levels, hydrate aggressively during the first 2 weeks of any new dose step. Stop and consult a licensed physician for severe or persistent GI symptoms, signs of pancreatitis, or any unusual side effect.
Dosing protocols
Retatrutide dosing is in U-100 syringe units. Semaglutide is sold as a pre-titrated pen, no unit math required. Both titrate slowly from the lowest dose.
Retatrutide (units)
20mg vial, 200u total, 0.1mg per unit
- Weeks 1 to 4: 2mg/wk = 20 units once weekly
- Weeks 5 to 8: 4mg/wk = 40 units once weekly
- Weeks 9 to 12: 8mg/wk = 80 units once weekly (may split 40u + 40u twice weekly for tolerability)
- Weeks 13 plus: 12mg/wk = 120 units (typically split 60u + 60u twice weekly)
See /reconstitution for the underlying U-100 math (1 unit equals 0.01mL).
Semaglutide (brand pen)
Wegovy FlexTouch pre-filled pen, pre-titrated
- Month 1: 0.25mg/wk
- Month 2: 0.5mg/wk
- Month 3: 1mg/wk
- Month 4: 1.7mg/wk
- Month 5 plus: 2.4mg/wk maintenance
Ozempic uses the same molecule with a 2mg/wk maximum (T2D indication). Both brands require a prescription. Peptara does not sell semaglutide.
The only mL number for retatrutide is the bac water input volume (2mL per 20mg vial). Every reta dose is in units. Reading a decimal place wrong on a small syringe barrel is the most common source of 10x overdoses, which is why protocol dashboards never display doses in mL.
Cost per month
Retatrutide cost is derived from Peptara vial price using the formula: cost per month equals vial price times 4.33 weeks per month, divided by weeks per vial. Semaglutide cost is quoted from US retail / compounding pharmacy reference points, not Peptara pricing.
Retatrutide via Peptara
$174 first-time per 20mg vial ($205 retail)
- 2mg/wk (start): about $75/mo first-time, about $89/mo retail
- 4mg/wk: about $151/mo first-time, about $178/mo retail
- 8mg/wk: about $301/mo first-time, about $355/mo retail
- 12mg/wk (maintenance): about $451/mo first-time, about $532/mo retail
Semaglutide reference (NOT Peptara)
External reference pricing only
- Wegovy 2.4mg/wk pen: about $1,349/mo US cash retail list (Novo Nordisk)
- Ozempic 2mg/wk pen: about $968/mo US cash retail list
- US compounded sema: about $200 to $400/mo (where legally compounded under FDA shortage policy)
Vietnam reality check
Wegovy and Ozempic are not officially imported into Vietnam. Gray-market import pricing is unverifiable and widely variable (observed range $500 to $1,500 per month). Peptara does NOT source or recommend gray-market semaglutide. Retatrutide is stocked locally and ships with a Certificate of Analysis.
Headline cost delta
Retatrutide via Peptara at peak 12mg/wk dose runs about $451/mo. Wegovy at peak 2.4mg/wk via US retail runs about $1,349/mo. The difference is roughly 67%, but the regulatory status is also fundamentally different (Wegovy FDA-approved, retatrutide research compound). This is a data observation, not medical advice. Make the decision with a licensed physician.
Who picks which
A short decision framework. No single right answer, just trade-offs that map cleanly to user profiles.
Pick Semaglutide (Ozempic / Wegovy) if
- You want an FDA-approved pharmaceutical drug
- You have insurance or local-market access
- You value multi-year safety data
- You prefer a pre-filled pen with no reconstitution
- You have access to a prescribing physician
Pick Retatrutide if
- You have a research / non-clinical context
- You understand it is not FDA-approved
- You accept Phase 3 trial data is still being collected
- You want the larger Phase 2 trial-peak effect
- You can self-administer with a U-100 insulin syringe after reading /reconstitution
Pick Tirzepatide (middle option) if
- You want an FDA-approved option (Mounjaro / Zepbound)
- You want stronger Phase 3 numbers than semaglutide
- SURMOUNT-1 Phase 3 hit -22.5% at 15mg/wk over 72 weeks
- See Retatrutide vs Tirzepatide for the full breakdown
Frequently asked questions
Next steps
Buy Retatrutide
20mg vial, $174 first-time ($205 retail). Triple-agonist research peptide with Phase 2 trial peak -24.2%. COA on request.
View product
Reconstitution math
4-step method, units-not-mL formula, calculator for all 15 SKUs. Required reading before your first retatrutide injection.
Open guide
Retatrutide vs Tirzepatide
The GLP-1 + GIP dual-agonist middle option, both FDA-approved and research-grade vials side by side. Phase 3 SURMOUNT-1 vs Phase 2 retatrutide.
Open comparison
Order Retatrutide, get a weekly titration protocol
Order Retatrutide from Peptara and we build your weekly titration protocol within 12 hours. Includes injection kit, bac water, and dosing chart in units.
Every order ships with bac water sized to the vial, a custom dashboard with your doses in units (never mL), and ongoing protocol support on WhatsApp.