Head to head
Retatrutide vs Ozempic: How the Fat-Loss Trials Compare
Published by Peptara Labs · Updated · How we research and check our pages
Retatrutide vs Ozempic: a 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.
- Price: Retatrutide is $174 per 20mg vial with email signup ($8.70 per mg). Brand semaglutide is a prescription pen whose price depends on insurance and pharmacy.
- Different trials, different durations, different cohorts. Compare data, then decide with a licensed physician.
TL;DR comparison
One table, every row that matters. The dose row shows only what each trial or label used, with its source. The recon row assumes the Peptara standard reconstitution (20mg vial in 2mL bac water, 200 units per vial, 0.1mg per unit), which is vial arithmetic, not a dose; semaglutide pens need no reconstitution. 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 (doi:10.1056/NEJMoa2301972)
- Phase: 2
- n: 338
- Duration: 48 weeks
- 12mg/wk: -24.2% mean body weight
- 8mg/wk: -22.8% · 4mg/wk: -17.1% · 1mg/wk: -8.7% · Placebo: -2.1% (all at 48 weeks)
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 often reported during titration in the trials
- Diarrhea
- Constipation
- Vomiting, more often at higher trial doses
- Decreased appetite (the mechanism itself)
Semaglutide-specific
- Years of clinical safety data (SUSTAIN, SELECT)
- FDA black-box warning: thyroid C-cell tumors (rodent data)
- Rare pancreatitis and gallbladder events
- In STEP-1, nausea and diarrhea were typically transient and mild to moderate (Wilding et al., 2021)
Retatrutide-specific
- Phase 2 GI events were dose-related and mostly mild to moderate (Jastreboff et al., 2023)
- Heart rate rose with dose in phase 2, peaking at 24 weeks and declining after
- Long-term safety still being established in Phase 3
- Research compound: no post-marketing surveillance data
Both trials raised the dose in steps under medical supervision, and the retatrutide trial reported fewer gastrointestinal events when an arm started at 2 mg rather than 4 mg (Jastreboff et al., 2023). That describes how the trials ran, not a plan for anyone to follow. Stop and consult a licensed physician for severe or persistent GI symptoms, signs of pancreatitis, or any unusual side effect.
Doses as studied in each trial
The retatrutide phase 2 trial assigned 338 adults to 1, 4, 8 or 12 mg once weekly, or to placebo, for 48 weeks (Jastreboff et al., 2023; doi:10.1056/NEJMoa2301972). STEP-1 assigned 1,961 adults to semaglutide 2.4 mg once weekly or placebo for 68 weeks (Wilding et al., 2021).
| Compound | Weekly dose arm (trial) | Route | Mean body-weight change | Source |
|---|---|---|---|---|
| Retatrutide | 1 mg | Subcutaneous, once weekly | -8.7% at 48 weeks | Jastreboff et al., 2023 (phase 2) |
| Retatrutide | 4 mg | Subcutaneous, once weekly | -17.1% at 48 weeks | Jastreboff et al., 2023 (phase 2) |
| Retatrutide | 8 mg | Subcutaneous, once weekly | -22.8% at 48 weeks | Jastreboff et al., 2023 (phase 2) |
| Retatrutide | 12 mg | Subcutaneous, once weekly | -24.2% at 48 weeks | Jastreboff et al., 2023 (phase 2) |
| Placebo (retatrutide trial) | None | Subcutaneous, once weekly | -2.1% at 48 weeks | Jastreboff et al., 2023 (phase 2) |
| Semaglutide | 2.4 mg | Subcutaneous, once weekly | -14.9% at 68 weeks (placebo -2.4%) | Wilding et al., 2021 (STEP-1, phase 3) |
These are the amounts the trials tested, reported for education. They are not a schedule, and no amount on this page is a dose for anyone to take. Both trials reached the higher amounts in steps under medical supervision. The brand labels set their own escalation for prescribed use, with label maximums of 2.4 mg once weekly for Wegovy and 2 mg once weekly for Ozempic. The retatrutide dosage page covers the phase 2 arms in more detail.
Vial math, not a dose: a 20mg retatrutide vial mixed with 2mL of bacteriostatic water gives 200 units on a U-100 syringe, so each unit holds 0.1mg. Reading a decimal place wrong on a small syringe barrel is the most common source of a tenfold misread, which is why the arithmetic is shown in units rather than mL. Semaglutide pens are pre-filled and need no reconstitution. See /reconstitution for the U-100 math (1 unit equals 0.01mL).
Price: retatrutide per vial and per mg
A 20mg retatrutide vial is $174 with email signup and $205 retail, which is $8.70 and $10.25 per mg. Semaglutide is not sold by Peptara, so its price is not quoted here.
Retatrutide via Peptara
$174 with email signup per 20mg vial ($205 retail)
Price of each phase 2 trial arm's weekly amount at the per-mg rate (Jastreboff et al., 2023). This is price arithmetic on the trial's arms, not a dose recommendation, and it does not divide a vial into weeks.
- 1 mg trial arm: $8.70 of material a week with email signup, $10.25 retail
- 4 mg trial arm: $34.80 of material a week with email signup, $41 retail
- 8 mg trial arm: $69.60 of material a week with email signup, $82 retail
- 12 mg trial arm: $104.40 of material a week with email signup, $123 retail
Semaglutide (NOT sold by Peptara)
Prescription brand pens
- Ozempic and Wegovy are prescription pens. What a patient pays depends on insurance, the pharmacy, and the manufacturer's current programs, so this page does not quote a figure.
- Peptara does not sell semaglutide in any form and does not source or recommend gray-market semaglutide.
Why there is no single cost ratio
Retatrutide is priced per milligram of research material; brand semaglutide is priced per prescription pen, with insurance and pharmacy terms on top. The regulatory status also differs: Wegovy is FDA-approved, and retatrutide is a research compound. A single cost ratio between the two would mislead, so this page gives the retatrutide figures and the arithmetic instead. For the full retatrutide breakdown, see the retatrutide price per vial.
How the options differ
Status, format, and evidence side by side. Any decision about using one belongs with a licensed physician.
Semaglutide (Ozempic / Wegovy)
- FDA-approved prescription drug
- Multi-year safety data, including cardiovascular outcome trials
- Pre-filled pen, no reconstitution
- Requires a prescribing physician
Retatrutide
- Research compound, not FDA-approved
- Phase 3 (TRIUMPH) data still being collected
- Phase 2 top arm: -24.2% at 48 weeks (Jastreboff et al., 2023)
- Lyophilized research vial that has to be reconstituted (see /reconstitution)
Tirzepatide (the dual agonist)
- FDA-approved as Mounjaro / Zepbound
- SURMOUNT-1 Phase 3 reported -22.5% at 15mg/wk over 72 weeks
- A separate trial from both of the above, not a head-to-head
- See Retatrutide vs Tirzepatide for the full breakdown
Frequently asked questions
Is retatrutide really better than Ozempic for weight loss?
Phase 2 trial peak was -24.2% mean body weight reduction at 12mg/wk over 48 weeks for retatrutide (Jastreboff et al, NEJM 2023). Phase 3 STEP-1 trial peak was -14.9% at 2.4mg/wk over 68 weeks for semaglutide / Wegovy (Wilding et al, NEJM 2021). The difference is roughly 9 percentage points, but these are different trials with different durations, different cohorts, and different sponsors. Phase 3 retatrutide data from the ongoing TRIUMPH program may report different numbers than Phase 2. Treat the gap as a data observation, not a controlled head-to-head finding.
Is retatrutide FDA-approved?
No. As of 2026, retatrutide is not FDA-approved for any indication. It is in Phase 3 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. Semaglutide brands Ozempic and Wegovy are FDA-approved (2017 and 2021 respectively).
Are Ozempic and Wegovy the same thing?
Both are brand-name semaglutide manufactured by Novo Nordisk. Ozempic was FDA-approved in December 2017 for type 2 diabetes, with a maximum dose of 2mg/wk. Wegovy was FDA-approved in June 2021 specifically for chronic weight management in adults with BMI of 30 or higher (or 27 with a weight-related comorbidity), with a higher maximum dose of 2.4mg/wk. Same molecule, different titration ceiling, different on-label indications.
Can I switch from semaglutide to retatrutide?
That is a medical decision for the prescribing physician. Retatrutide has not been studied in people switching from semaglutide, and this site gives no switching, washout or starting-dose instructions. Do not stop or change FDA-approved therapy without the prescribing doctor. Peptara does not provide medical advice.
What are the side effects of retatrutide vs semaglutide?
Both share the GLP-1 class side-effect profile: nausea, diarrhea, constipation, and vomiting. In the retatrutide phase 2 trial, gastrointestinal events were the most common adverse events; they were dose-related, mostly mild to moderate, and partly reduced when an arm started at 2 mg rather than 4 mg (Jastreboff et al., 2023). In STEP-1, nausea and diarrhea were the most common adverse events with semaglutide, and they were typically transient and mild to moderate (Wilding et al., 2021). Semaglutide has years of clinical safety data, including cardiovascular outcome trials (SUSTAIN, SELECT). Long-term retatrutide safety is still being established in phase 3 trials.
Does Peptara sell Ozempic or Wegovy?
No. Peptara stocks retatrutide and other research peptides, but does not sell semaglutide vials, semaglutide pens, Ozempic, or Wegovy in any form. Ozempic and Wegovy require a prescription from a licensed physician and are dispensed by pharmacies that carry the brand pen. Peptara does not source or recommend gray-market semaglutide imports.
Why aren’t Ozempic and Wegovy officially available in Vietnam?
As of 2026, Novo Nordisk has not registered Ozempic or Wegovy with the Vietnam Ministry of Health for local distribution. Gray-market imports exist (typically sourced from Thailand, Singapore, or elsewhere), but the supply chain is unverifiable and pricing varies widely (observed range $500 to $1,500 per month). Peptara does not source gray-market semaglutide because chain-of-custody cannot be guaranteed. Retatrutide is stocked locally and ships with a Certificate of Analysis.
How much weight do most users lose on each?
Only trial averages exist: retatrutide -24.2% at the 12 mg weekly arm (phase 2, 48 weeks; Jastreboff et al., 2023) and semaglutide / Wegovy -14.9% at 2.4 mg weekly (STEP-1, phase 3, 68 weeks; Wilding et al., 2021). These are population means from separate supervised trials, not predictions for any person, and research-grade material used outside a trial has no outcome data of its own.
Next steps
Buy Retatrutide
20mg vial, $174 with email signup ($205 retail). Triple-agonist research peptide; its phase 2 trial reported up to -24.2%. COA on request.
View product
Reconstitution math
4-step method, units-not-mL formula, calculator for the catalog vials. The arithmetic behind every unit figure, for any vial size and water volume.
Open guide
Retatrutide vs Tirzepatide
The GLP-1 + GIP dual agonist compared with retatrutide on trial data and price: Phase 3 SURMOUNT-1 vs the Phase 2 retatrutide trial.
Open comparison
Order Retatrutide with its batch certificate
Order Retatrutide from Peptara: third-party tested material with its batch certificate and bacteriostatic water for the vial.
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