Peptides
Retatrutide
Also called Reta · Triple-G
Retatrutide is an experimental weekly injection attracting interest for substantial weight loss and appetite-related effects. It adds a third hormone pathway to the approach used by tirzepatide. Large trials have reported results, but retatrutide remains unapproved and has no approved prescribing dose.
Dosage & duration
Investigational trial example · adults with obesity without diabetes · not an approved dosing schedule.
TRIUMPH-1 · phase 3 obesity trial
Published example · product-specific- Dose
- Trial start: 2 mg. Fixed 4-week steps led to an assigned target of 4, 9 or 12 mg.
- How often
- Once weekly, injected under the skin
- How long
- 80-week main trial; not a recommended treatment cycle
The higher-target arms used intermediate doses; reductions were allowed under trial supervision. These amounts describe the studied product and protocol, not an approved starting or maintenance prescription.
A trial target is not a dose conversion from semaglutide or tirzepatide. Trial results do not verify a product sold online under the same name.
More quick facts
The practical difference
Retatrutide and tirzepatide: practical differences
The additional hormone target is only one part of the comparison. Current availability and prescribing evidence also matter.
| What changes | Retatrutide | Tirzepatide |
|---|---|---|
| Current US status | Investigational; no FDA approval | Approved products include Zepbound and Mounjaro |
| Hormone targets | GLP-1 + GIP + glucagon | GLP-1 + GIP |
| Dose information | Named research protocols | Product-specific prescribing labels |
Why are people interested in retatrutide?
The appeal is the possibility of substantial weight loss, particularly for people comparing it with semaglutide or tirzepatide. Retatrutide acts on GLP-1, GIP and glucagon pathways. Adding glucagon activity is a different biological approach; it does not by itself prove stronger appetite control, better energy or fewer side effects.
In the latest published TRIUMPH-1 trial, adults with obesity without diabetes had average weight reductions of 17.6%, 23.7% and 25.0% in the 4, 9 and 12 mg target groups at 80 weeks, compared with 3.9% on placebo. Those figures include the trial’s handling of people who stopped or changed treatment. They are results after supervised escalation and many months of follow-up.
Why it comes up in cutting and bulking discussions
Some bodybuilders hope for easier cutting, more energy and staying lean while eating more. Some also ask about insulin sensitivity during a growth phase. These are motivations, not established benefits for a lean lifter.
Experiences conflict. Some users report easier appetite control; others describe fatigue or digestion that makes large training meals difficult. Impressive reported transformations may also involve testosterone, other compounds and major diet changes. They cannot show what retatrutide caused, whether muscle was preserved or what another person should expect. The obesity-trial results do not establish a bodybuilding or bulking regimen.
Is it better than tirzepatide or semaglutide?
A higher percentage from a separate study is not a direct comparison. Study length, participants, dose changes and how stopped treatment is counted all affect the result. The direct retatrutide-versus-tirzepatide study, TRIUMPH-5, has not posted results as of this source check.
The practical difference today is that semaglutide and tirzepatide have approved products with prescribing information. Retatrutide remains investigational. A vial sold online does not acquire the identity, quality or clinical evidence of the trial product just because its label says retatrutide.
What did the trial schedule involve?
The opening guide describes TRIUMPH-1’s supervised escalation and study duration. Target amounts were reached gradually, with reductions available for tolerability, inadequate food intake or excessive weight loss. Research follow-up is not an approved cycle or a safe self-directed escalation plan.
Which side effects are people concerned about?
Nausea, diarrhea, vomiting and constipation are the main familiar concerns from obesity trials. The earlier phase 2 trial also found dose-related heart-rate increases. More recent phase 3 work reported altered skin sensation, sometimes described as tingling, burning or unusual sensitivity, and low blood pressure. These are reasons to assess tolerability alongside weight change, not to assume that a more intense reaction means better fat loss.
Online accounts of appetite, energy or side effects cannot establish that retatrutide will solve a problem someone experienced on another medicine. New palpitations, fainting, severe abdominal pain or persistent vomiting need medical assessment rather than a change based only on a plot.
Model details: Retatrutide · estimated
How to read this estimate
Estimated from study endpoints; the curve between measurements is reconstructed. Compare amounts and timing in mg.
A concentration estimate reconstructed from the stated source dose and timing.
Assumptions, calculation and sources
LY3437943 trial injection, prepared from 5 mg vials reconstituted with sterile water or saline.. subcutaneous. Healthy adults, Singapore single-ascending-dose study; 1 mg cohort n=6..
retatrutide: estimated concentration in plasma (ng/mL).
Coskun 2022 Table 1, 1 mg cohort: geometric mean terminal half-life134h; median Tmax48h.
- Calibration dose
- 1 mg
- Reported calibration peak
- 110 ng/mL
- Peak timing used
- 48 hours
- Terminal half-life used
- 134 hours
- Reconstructed absorption rate
- 0.05406351 /hour
- Observed extravascular concentrations already contain bioavailability; do not multiply by legacy F or add an independently assumed F.
- Dose scaling and repeated-dose superposition use fixed parameters; the example dose does not calibrate the curve.
- Linear dose scaling/repeated-dose superposition is an approximation, although the trial describes nearly proportional PK.
- Other dose cohorts differ; the estimate is not a pooled population fit and does not recreate every dose-cohort mean.
- No molecular-weight conversion is required; do not preserve old nmol/L label over ng/mL values.
- Coskun et al. 2022, Cell Metabolism, Table 1
1 mg single SC: Cmax110ng/mL; Tmax48h; half-life134h; AUCinf28300ng*h/mL. Publisher full text including table was inspected through search index; direct publisher fetch returned403.
- NCT03841630
Identifies healthy-adult first-in-human single-dose trial.
Estimate retatrutide-source-estimate-2026-10 · version 1
Common questions
Why do some headlines say 28.3% rather than 25.0% weight loss?
They describe different analyses of the same 12 mg TRIUMPH-1 group at 80 weeks. The 28.3% estimate assumes participants remained on study treatment without prohibited weight-management treatments; 25.0% describes the treatment-regimen analysis regardless of adherence. Neither is an individual prediction.
Can a trial target such as 9 or 12 mg be used as a starting dose?
Those were assigned later targets in TRIUMPH-1. Participants began at 2 mg and followed supervised escalation. The study does not provide an approved public-use prescription or validate an online product.
Is retatrutide a GLP-3 medicine?
“GLP-3” is an informal nickname, not the name of a third GLP hormone. Retatrutide activates three different receptor pathways: GLP-1, GIP and glucagon.
Does it reliably suppress appetite more than tirzepatide?
The cited evidence does not establish that comparison for an individual. Large weight-loss results do not mean everyone feels less hunger, and the direct tirzepatide comparison has not yet reported results in the checked registry.
Sources Labels, studies and notes behind this guide
Catalog evidence: Human clinical trials. This describes the type of evidence, not a clinical review of every claim.
Summary and fact source checks: 2026-10-07. This records source checking, not medical review of the whole page.
Notes on the quick facts
- 80-week obesity trial · no diabetes
- TRIUMPH-1 treatment-regimen analysis includes outcomes regardless of adherence. This is a group mean after trial escalation, not a starting-dose forecast.
- What is different?
- Retatrutide activates GLP-1, GIP and glucagon receptors. Tirzepatide activates GLP-1 and GIP; semaglutide activates GLP-1.
- Trade-offs reported in studies
- Findings come from different trials; they are not a single incidence estimate. Altered skin sensation is also called dysesthesia.
- 1. Jastreboff et al. 2026 — TRIUMPH-1 obesity trial
Published September 29, 2026. Adults with obesity without diabetes; randomized weekly 4/9/12 mg targets or placebo for 80 weeks. Treatment-regimen/ITT weight changes −17.6/−23.7/−25.0% versus −3.9% placebo. Uses the original paper’s analysis, not the larger adherence-assuming headline estimate.
- 2. Lilly — retatrutide status, updated September 2026
Current sponsor FAQ checked October 7: investigational, not FDA approved or available as an approved public-use medicine. Describes three receptor targets; “GLP-3” is not a distinct hormone classification. No launch date or retail-product equivalence inferred.
- 3. Lilly — TRIUMPH-1 doses and analysis definitions
Sponsor’s original May 21, 2026 release: start 2 mg weekly; fixed four-week steps toward assigned 4, 9 or 12 mg target (9 mg via 2/4/6; 12 mg via 2/4/6/9). Main period 80 weeks; a selected subgroup entered a 24-week extension. Defines 28.3% efficacy-estimand versus 25.0% treatment-regimen result; these are different analyses, not different doses.
- 4. Giblin et al. — TRIUMPH program design
Original design paper: weekly SC trial targets, fixed escalation and 80-week TRIUMPH-1 period; protocol allowed reductions for tolerability, inadequate intake or excessive weight loss. Trial conduct does not establish a public prescribing regimen.
- 5. Zepbound US prescribing information — August 2026
Approved tirzepatide weight-management product, GIP/GLP-1 activity and product-specific dosage; comparator identity/status only. Not a dose-conversion or cross-trial efficacy source.
- 6. Wegovy US prescribing information — June 2026
Approved semaglutide weight-management product and GLP-1 activity; comparator identity/status only. A different drug, not an equivalent retatrutide dose.
- 7. TRIUMPH-2 phase 3 trial — adults with type 2 diabetes, 2026
Published September 29, 2026. Separate 80-week trial in adults with BMI ≥27 and type 2 diabetes; reported GI events, hypotension and dysesthesia. Used to establish these reported concerns, not to compare incidence across unrelated trials.
- 8. Jastreboff et al. 2023 — retatrutide phase 2
Original 48-week obesity trial. Dose-related GI symptoms; heart-rate increases peaked around week 24 then declined. This does not show that palpitations are harmless or validate the stored legacy exposure model.
- 9. TRIUMPH-5 — direct retatrutide versus tirzepatide trial
Live registry/API checked October 7: active, not recruiting; no results posted. No head-to-head superiority result is claimed. Completion dates are estimates, not a promised publication date.
- 10. Mounjaro US prescribing information — August 2026
Approved tirzepatide product for type 2 diabetes and specified adult cardiovascular-risk reduction; comparator status, not retatrutide dose equivalence.
- 11. Coskun et al. 2022, Cell Metabolism, Table 1
1 mg single SC: Cmax110ng/mL; Tmax48h; half-life134h; AUCinf28300ng*h/mL. Publisher full text including table was inspected through search index; direct publisher fetch returned403.
- 12. NCT03841630
Identifies healthy-adult first-in-human single-dose trial.
Keep reading
Related compounds and examples
Related compounds
Semaglutide Injection (Ozempic/Wegovy)
Semaglutide can reduce hunger and food intake, helping people lose weight. Wegovy injections are prescribed for weight management; Ozempic injections treat type 2 diabetes. Both are taken weekly, with gradual dose increases to help manage digestive side effects.
Semaglutide Oral (Rybelsus)
Oral semaglutide offers a daily tablet option for adults with type 2 diabetes who want to avoid injections. The morning routine matters: food, drink and other tablets affect absorption, and different semaglutide products cannot be compared milligram for milligram.
Tirzepatide (Mounjaro)
Tirzepatide can reduce appetite and food intake, helping people lose weight and improve blood-sugar control. In the US, Zepbound is the weight-management brand and Mounjaro treats type 2 diabetes. Both are weekly injections; digestive side effects and the right dose for the treatment goal are the main practical trade-offs.