Ipamorelin vs Retatrutide: Side-by-Side Comparison
A comprehensive comparison of Ipamorelin and Retatrutide: mechanism, dosage, approval status, clinical results, side effects, and which is right for your goals.
Ipamorelin
AKA: NNC 26-0161
A selective growth hormone secretagogue that boosts GH release with minimal side effects — popular for anti-aging and body composition.
Investigational / ResearchRetatrutide
AKA: LY3437943, triple agonist peptide
The most powerful weight loss peptide in clinical development, targeting three metabolic receptors simultaneously.
Investigational / ResearchHead-to-Head Comparison
| Category | Ipamorelin | Retatrutide |
|---|---|---|
| Class | Growth Hormone Secretagogue (GHRP) | GIP/GLP-1/Glucagon Triple Receptor Agonist |
| Typical Dose | 200-300 mcg 1–3 times daily (often before bed and/or around workouts) | 8-12 mg Once weekly |
| Half-Life | ~2 hours | ~7 days (weekly dosing enabled) |
| Administration | Subcutaneous injection | Subcutaneous injection (abdomen, thigh, upper arm) |
| FDA Approval | No FDA approval. Research use only. | Phase 3 clinical trials; anticipated FDA filing 2026–2027 |
| Primary Uses | Growth hormone stimulation, Body composition improvement, Anti-aging, Sleep quality enhancement, Recovery optimization | Weight loss, Obesity management, Metabolic syndrome, Type 2 diabetes (investigational) |
| Legal Status | Research chemical in the US. Not FDA approved. Available through peptide research suppliers. | Investigational (not yet FDA approved). Not legally available for human use outside of clinical trials in the US. |
Clinical Trial Outcomes: What the Data Shows
The following data comes from Phase 2/3 trials. These trials used different populations, durations, and endpoints — direct comparison is directional, not definitive.
| Metric | Ipamorelin | Retatrutide |
|---|---|---|
| Drug class | Growth Hormone Secretagogue (GHRP) | GIP/GLP-1/Glucagon Triple Receptor Agonist |
| Peak weight loss (mean, max dose) | See trial data | 24.2% (48 weeks) |
| Trial population | See published trials | N=338, TRIUMPH-1 |
| FDA approval (obesity) | Not approved — investigational | Not approved — investigational |
| Thermogenesis mechanism | Minimal | Yes — glucagon receptor |
Side Effects Comparison
Ipamorelin
Retatrutide
Who Should Choose Which?
Choose Ipamorelin if:
- • You want growth hormone stimulation
- • You are comfortable with investigational compounds and clinical trial enrollment
- • Subcutaneous injection is your preferred route
- • You are willing to wait for FDA approval (projected 2027–2028) or can enroll in an active trial
Choose Retatrutide if:
- • You want weight loss
- • You are comfortable with investigational compounds
- • You want the thermogenesis advantage from glucagon receptor activation
- • Subcutaneous injection (abdomen, thigh, upper arm) is your preferred route
Switching From One to the Other
If you are currently on Retatrutide and considering switching to Ipamorelin (or vice versa), here is what to plan for:
Switching from Retatrutide to Ipamorelin
- • Eligibility: Ipamorelin is only available in clinical trials. Standard prescription switching is not yet possible.
- • Washout: Weekly GLP-1 drugs typically require 4–8 weeks washout due to extended half-lives (~7 days). Overlapping two GLP-class drugs increases GI side effect risk.
- • Re-titration: Start at the lowest dose of the new drug and re-titrate — even if you tolerated high doses of the previous drug.
- • Expect adjustment: 4–12 weeks for full receptor adaptation to the new molecule.
Switching from Ipamorelin to Retatrutide
- • Access: Retatrutide is investigational.
- • Washout: Same 4–8 week washout principle applies — allow the first drug to clear before starting the second.
- • Weight: Expect some weight regain during the washout period as appetite normalizes without active drug coverage.
- • Indication: Ensure Retatrutide is appropriate for your indication — approval status and coverage differ.
Frequently Asked Questions
What is the main difference between Ipamorelin and Retatrutide?
Ipamorelin (Growth Hormone Secretagogue (GHRP)) and Retatrutide (GIP/GLP-1/Glucagon Triple Receptor Agonist) differ in their receptor targets, mechanism of action, and clinical applications. Ipamorelin: A selective growth hormone secretagogue that boosts GH release with minimal side effects — popular for anti-aging and body composition. Retatrutide: The most powerful weight loss peptide in clinical development, targeting three metabolic receptors simultaneously.
Which is better for weight loss — Ipamorelin or Retatrutide?
Both Ipamorelin and Retatrutide may support weight loss, but their approved indications and clinical evidence differ. Ipamorelin approval: No FDA approval. Research use only.. Retatrutide approval: Phase 3 clinical trials; anticipated FDA filing 2026–2027. Consult a healthcare provider to determine which is appropriate for your situation.
Can you take Ipamorelin and Retatrutide together?
Combining Ipamorelin and Retatrutide has not been studied in clinical trials and is not recommended without direct medical supervision. The pharmacological overlap between them may increase the risk of side effects.
Is Ipamorelin stronger than Retatrutide?
Ipamorelin and Retatrutide have different mechanisms and have not been directly compared in head-to-head trials. The available trial data for each drug was generated in different populations and timeframes, making direct comparison difficult.
Which should I choose — Ipamorelin or Retatrutide?
The choice depends on your specific goals, medical history, cost considerations, and physician guidance. Review the mechanism, dosing, and side effect profiles of each with a healthcare provider before deciding.
Can I switch from Retatrutide to Ipamorelin?
Switching between GLP-class drugs is possible but requires a washout period and physician oversight. For weekly injectable GLP-1 drugs, a typical washout is 4–8 weeks due to the extended half-life. Switching while Ipamorelin remains investigational is not a standard clinical option — you would need to enroll in a clinical trial or wait for FDA approval. Discuss transition planning with your prescribing physician.