Retatrutide
Also called LY3437943; "triple agonist"
An investigational once-weekly medicine from Eli Lilly that activates three hormone receptors: GIP, GLP-1 and glucagon. Phase 3 trials report substantial weight loss, but it is not FDA approved.
Overview
What it is
A single peptide molecule with triple-receptor activity. It is not a mixture of semaglutide and tirzepatide, and it is not a stronger version of Ozempic.
How it works
GLP-1 and GIP shape the body's response to food and blood sugar; glucagon signaling adds effects on energy use and the liver. More targets do not automatically mean a better treatment for every person.
What the research shows
A 2023 phase 2 trial in obesity showed large dose-related weight loss over 48 weeks. TRIUMPH-1 (adults with obesity, no diabetes) and TRIUMPH-2 (adults with type 2 diabetes) were published in September 2026; in TRIUMPH-2 the highest-dose group lost 18.8% on average (20.8% under the sponsor's efficacy analysis). TRIUMPH-1 also reported improvements in knee osteoarthritis and sleep apnea subgroups.
Studied for
- Obesity without diabetesphase 3
- Obesity with type 2 diabetesphase 3
- Knee osteoarthritis and sleep apneasubgroups
Safety and regulatory status
Safety and side effects
In TRIUMPH-2's highest-dose group, diarrhea occurred in 34% (13% placebo) and nausea in 28% (8% placebo). Low blood pressure (6% vs under 1%) and unusual skin sensations (7% vs 1%) were also reported. Heart rate rose in a dose-related way in phase 2, peaking around week 24.
Regulatory status
Not FDA approved as of October 2026. FDA says it cannot legally be used in compounding. Lilly plans a US submission in early 2027.
Mixing and dosing reference
Reference information only. Read before using this section.
Retatrutide Dosage Protocol (20 mg Vial)
- Vial
- 20 mg Retatrutide
- Add diluent
- 2 mL
- Concentration
- 10 mg/mL
- 1 unit (U-100)
- 100 mcg in 0.01 mL
- Route
- Subcutaneous
- How often
- Once weekly by subcutaneous administration in the cited human trials.
- Typical range
- The cited programs evaluated target amounts through 12 mg weekly.
Phase 2 Trial Schedule
| Study Phase | Weekly Dose | U-100 Units | Volume |
|---|---|---|---|
| Weeks 1 to 4 | 2 mg | 20 units | 0.2 mL |
| Weeks 5 to 8 | 4 mg | 40 units | 0.4 mL |
| Weeks 9 to 12 | 8 mg | 80 units | 0.8 mL |
| Weeks 13+ | 12 mg | 120 units | 1.2 mL |
Phase 3 Trial Schedule
| Study Phase | Weekly Dose | U-100 Units | Volume |
|---|---|---|---|
| Weeks 1 to 4 | 2 mg | 20 units | 0.2 mL |
| Weeks 5 to 8 | 4 mg | 40 units | 0.4 mL |
| Weeks 9 to 12 | 6 mg | 60 units | 0.6 mL |
| Weeks 13 to 16 | 9 mg | 90 units | 0.9 mL |
| Weeks 17+ | 12 mg | 120 units | 1.2 mL |
How to mix
- Clean the vial stopper and gather the sterile supplies required by the research procedure.
- Add 2 mL bacteriostatic water slowly down the vial wall.
- Gently swirl or roll until dissolved. Do not shake.
- Label the vial 10 mg/mL with the preparation date and follow the documented refrigerated storage period.
Dosing details
- Phase 2 and phase 3 used related but distinct dose-escalation designs.
- Phase 2 lower-start 12 mg arm: 2 mg, 4 mg, 8 mg, and then 12 mg in four-week stages.
- Phase 3 12 mg target: 2 mg, 4 mg, 6 mg, 9 mg, and then 12 mg in four-week stages.
- Other target groups: The programs also studied lower assigned targets rather than escalating every participant to 12 mg.
- Measurement: The primary chart shows weekly peptide mass, U-100 units, and mL together.
- Strength consistency: The same research amount has the same peptide mass across every Retatrutide vial size; only the concentration and required volume change.
- The phrase Retatrutide dosing schedule can refer to several different clinical trial protocols. There is no single approved schedule because Retatrutide is still investigational and is not yet approved as a weight loss medication.
- In the phase 2 obesity trial, the lower-start 12 mg group used a 2 mg starting dose. The Retatrutide dose then increased to 4 mg, 8 mg, and the assigned 12 mg dose in four-week stages.
- The phase 3 clinical trials use related but distinct schedules. For a 12 mg target, the protocol progresses through 2 mg once weekly, 4 mg, 6 mg, 9 mg, and 12 mg once weekly, with four weeks at each escalation step.
- The term maintenance dose describes the assigned target phase inside that trial. It is not a recommendation to start Retatrutide, take Retatrutide, or adjust doses of Retatrutide outside a study.
- Anyone interpreting a published starting dose or maintenance dose should confirm the population, formulation, inclusion criteria, monitoring plan, and trial endpoint. A healthcare provider can explain how clinical trial evidence differs from individualized care; this research page does not provide personalized dosing.
Storage
- Storage and handling must follow the documentation for the exact formulation used.
- Before preparation: Keep a lyophilized vial dry, protected from light, and at the temperature stated in its product documentation.
- After preparation: Refrigerate only as permitted by the exact formulation and diluent instructions.
- Labeling: Record the 10 mg/mL concentration, preparation date, storage conditions, and documented discard date.
- Handling: Avoid vigorous shaking and unnecessary temperature cycling because peptide stability can be formulation-dependent.
Protocol source: PeptideDosages.com
Common questions
Is retatrutide the same as Ozempic?
No. Ozempic is semaglutide, a different molecule.
Is it better than tirzepatide?
No head-to-head trial exists; comparing numbers across separate trials is misleading.
Does the trial data mean online products are safe?
No. Trial results apply to the studied product, not products of unknown origin.
Related in Metabolic Health
Sources and further reading (5)
- TRIUMPH-1 phase 3 trial of retatrutide in obesity. NEJM, 2026.
- TRIUMPH-2 phase 3 trial in overweight or obesity with type 2 diabetes. Lancet, 2026.
- Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity: phase 2. NEJM, 2023.
- FDA. Concerns with unapproved GLP-1 drugs used for weight loss.
- Source summary: PeptideDosages.com research overview (rewritten for NVO).
Laboratory research material: GLP-3R (NVO research code) Research Use Only