GLP-1 receptor
GLP-1 receptor activation helps reduce hunger, slows gastric emptying, and supports glucose-dependent insulin release. Together, those effects can make smaller meals more satisfying while improving post-meal glucose control.
Back to Peptide Library
Triple Receptor Agonist
Retatrutide
LY3437943 • GIP / GLP-1 / Glucagon
Retatrutide is an investigational peptide that activates GIP, GLP-1, and glucagon receptors. Its Phase 3 trials have reported substantial weight loss, while gastrointestinal effects, altered skin sensation, and long-term safety remain important considerations.
At a glance
Retatrutide Quick Reference
- Community start
- Members onlySign in to view dosing details.
- Trial targets
- Members onlySign in to view dosing details.
- Titration
- 4+ weeksTrial escalation interval
- Route
- SubQ InjectionOnce weekly in trials
Overview
What Is Retatrutide?
Retatrutide (LY3437943), sometimes called “Triple G,” is a single peptide designed to activate GIP, GLP-1, and glucagon receptors. Eli Lilly is developing it as a once-weekly subcutaneous treatment for obesity, type 2 diabetes, and related metabolic conditions.
Semaglutide targets GLP-1; tirzepatide targets GIP and GLP-1. Retatrutide adds glucagon-receptor activity. Together, these pathways affect appetite, glucose regulation, and energy expenditure.
TRIUMPH-1 reported average weight loss of 28.3% at 80 weeks in the 12mg group and 19.0% in the 4mg group. Those results are trial outcomes under a structured escalation schedule, not predictions for lower-dose community use.
For other compounds studied for weight management, see Eloralintide, Survodutide, and Tesofensine.
Mechanism
Retatrutide Mechanism of Action
GIP receptor
GIP adds a second glucose-dependent incretin signal at the pancreatic beta cell. Its contribution may also change how the combined drug affects appetite and energy balance, though the contribution of each receptor cannot be isolated from the clinical results.
Glucagon receptor
Glucagon-receptor activation distinguishes Retatrutide from GLP-1/GIP dual agonists. Glucagon signaling is associated with energy expenditure and fuel use; how much it contributes to weight loss in people remains a mechanistic question.
Combined response
One molecule engages all three pathways rather than requiring a multi-drug stack. The combined signal produced substantial weight loss in controlled trials, but it also brought dose-related gastrointestinal effects and dysesthesia; trial outcomes do not reveal the exact contribution of each receptor.
Research findings
Retatrutide Benefits
Trial findings are distinct from lower-dose community reports and do not establish an outcome for every user.
Weight Reduction
TRIUMPH-1 reported 19.0% average weight loss at 4mg and 28.3% at 12mg after 80 weeks. That dose response was observed under a structured trial schedule in adults with obesity or overweight, not in lower-dose community use.
Waist Reduction
In TRIUMPH-1, waist circumference fell by as much as an average 24.1cm (9.5in) at 12mg over 80 weeks. Waist change helps show that the trial effect extended beyond the number on the scale, though it does not establish where every participant lost fat.
Appetite Control
GLP-1 and GIP signaling can alter satiety and meal size, while glucagon may add another influence on energy balance. Many community users describe less food noise, but appetite response and tolerability vary substantially.
Glucose Research
In TRANSCEND-T2D-1, adults with type 2 diabetes had average A1C reductions of up to 2.0 percentage points at 40 weeks. TRIUMPH-2 later reported reductions of up to 1.6 points at 80 weeks; these findings come from diabetes trial populations.
Energy Expenditure
Glucagon-receptor activity is the key mechanistic difference from dual GIP/GLP-1 agonists. It is associated with increased energy expenditure and altered fuel use, but the trials do not quantify how much of the observed weight loss came from that pathway alone.
Cardiometabolic Markers
TRIUMPH-1 reported improvements in triglycerides, non-HDL cholesterol, and systolic blood pressure alongside weight and waist measures. Those are cardiovascular risk factors, not proof that Retatrutide prevents heart attacks or strokes.
Protocol planning
Retatrutide Dosing Protocol
Members Access Only
Sign in or create a free account to view this content.
Preparation
Retatrutide Reconstitution
Reconstitution Example
10mg vial + 1mL bacteriostatic water
Result10mg/mL
Reconstitution steps
1
Prepare
Wash your hands, clean the work surface, and wipe both vial stoppers with alcohol. Allow them to dry.
2
Add diluent slowly
Use a new sterile syringe and needle to direct the selected volume of compatible diluent down the inside wall of the vial.
3
Dissolve gently
Swirl or roll the vial until the contents dissolve; do not shake.
4
Storage
Store refrigerated at 2–8°C (36–46°F) and protected from light when the product instructions support this. Record the reconstitution date in your research journal.
N=1 reports
Retatrutide Community Experience
Self-reported anecdotal experiences aggregated from public & private peptide community discussions and anonymous peptideprotocols.app user reports. This information does not carry the same weight as published research.
Positive Reports
- Reduced cravings and food noise are recurring reports.
- Some users describe stronger appetite suppression than they experienced with tirzepatide.
- Some report steadier appetite control through the week.
Negative & Mixed Reports
- Nausea, diarrhea, constipation, reflux, and vomiting often worsen after dose increases.
- Aggressive appetite suppression can make adequate protein and fluid intake difficult.
- Tingling, burning, or unusual skin sensitivity resembles the dysesthesia signal in trials.
Stacking & synergy
Retatrutide Stacking & Synergy
Combination research is limited. Track nutrition, resistance training, side effects, and each added compound separately.
Retatrutide + 5-Amino-1MQ
Discussed for separate body-composition mechanisms; no controlled study establishes additive benefit.
Retatrutide + AOD-9604
Community fat-loss pairing with no established incremental effect over Retatrutide alone.
Retatrutide + MOTS-c
Metabolic and performance interest is mechanistically distinct, but combination outcomes remain untested.
Retatrutide + Cagrilintide
Adds an amylin pathway to appetite regulation; overlapping adverse effects deserve attention.
Retatrutide + Tesamorelin
Sometimes discussed for visceral-fat goals; distinguish each compound’s evidence and side effects.
Retatrutide + ATX-304 (ATX-304)
ATX-304 (O-304) targets AMPK and skeletal-muscle glucose use, a different metabolic pathway from Retatrutide’s receptor activity. The pairing is a research hypothesis; no study has shown that it adds fat loss or preserves muscle during Retatrutide use.
Safety notes
Retatrutide Side Effects & Safety
Gastrointestinal effects are the leading tolerability issue, especially during escalation. TRIUMPH-1 also identified dose-related dysesthesia. At 12mg, adverse-event discontinuation was 11.3%, compared with 4.1% at 4mg and 4.9% with placebo.
Commonly Reported Effects
- Nausea, vomiting, diarrhea, constipation, or reflux.
- Reduced appetite that can make hydration and nutrition difficult.
- Fatigue and injection-site reactions.
Other Concerns
- Dysesthesia: tingling, burning, tenderness, or unusual skin sensitivity; 12.5% at 12mg versus 0.9% with placebo in TRIUMPH-1.
- Dehydration and electrolyte disturbance from persistent GI symptoms.
- Small increases in resting heart rate were observed in earlier trials.
- Rapid weight loss can increase lean-tissue loss without adequate protein and training.
Retatrutide Precautions
Avoid or Discuss With a Clinician If
- Pregnancy or breastfeeding.
- Severe or persistent vomiting, abdominal pain, or dehydration.
- A history of pancreatitis, gallbladder disease, or major gastrointestinal disease.
- Personal or family history of medullary thyroid carcinoma or MEN2; these groups were excluded from TRIUMPH-1.
Use Caution With
- Insulin or sulfonylureas, which can increase hypoglycemia risk as food intake changes.
- Difficulty meeting protein, fluid, or calorie needs.
- Neurologic symptoms or dysesthesia during escalation.
- Oral medicines whose timing may be affected by delayed gastric emptying.
Retatrutide is not FDA approved. FDA says it cannot be used in compounding under federal law.
Final verdict
Peptide Protocols Verdict on Retatrutide
Not medical advice. This editorial is our own opinion piece based off the experience of our own lab rats.
Our opinionated opinion
Retatrutide was the compound that first got us into peptides, and we have longer-term N=1 experience with it. We still rank it at the top for body-recomposition interest. Appetite control and fat loss have been striking in our experience, but that does not mean everyone should chase a higher dose.
For us, side effects began to creep in after roughly 14 weeks as we reached 2mg. We have not found going above that tolerable. More recently, we have noticed GI upset and nausea after eating. When those effects appear, we favor stepping back toward the amount that still works while leaving room to eat enough, hydrate, and train. We would not claim proven muscle sparing from Retatrutide itself; resistance training and adequate protein remain the real safeguards.