Ipamorelin vs Retatrutide
A detailed comparison to help you understand the differences and choose the right peptide for your research goals.
Ipamorelin
Ipamorelin is a selective growth hormone secretagogue that stimulates the release of growth hormone from the pituitary gland without significantly affecting cortisol or prolactin.
Full details →Retatrutide
Retatrutide (LY3437943) is a first-in-class triple agonist peptide targeting GIP, GLP-1, and glucagon receptors simultaneously. Developed by Eli Lilly, it is currently in Phase 3 clinical trials and has demonstrated the highest weight loss of any obesity medication to date — up to 28.7% body weight reduction at 48 weeks. The triple-receptor mechanism represents the next evolution beyond dual agonists like tirzepatide.
Full details →Side-by-Side Comparison
| Aspect | Ipamorelin | Retatrutide |
|---|---|---|
| Dose Range | 100 mcg–300 mcg | 4 mg–12 mg |
| Frequency | 2x daily | Less than daily |
| Cycle Length | 8–12 weeks | — |
| Route | subcutaneous | subcutaneous |
| Mechanism | Acts as a ghrelin mimetic, binding to the ghrelin receptor (GHS-R) in the pituitary to stimulate GH release. Highly selective with minimal effect on other hormones. | Retatrutide is a synthetic peptide that activates three incretin/metabolic hormone receptors: (1) GLP-1 receptor — appetite suppression, insulin secretion, delayed gastric emptying, (2) GIP receptor — enhanced insulin sensitivity, improved fat metabolism, (3) Glucagon receptor — increased energy expenditure, hepatic fat mobilization, thermogenesis. The glucagon receptor component is the key differentiator, adding an energy-expenditure mechanism absent from GLP-1 and dual GIP/GLP-1 agonists. The molecule uses a C20 fatty diacid for albumin binding, enabling once-weekly dosing. |
| Typical Dosage | Typical dosing ranges from 200-300mcg administered 2-3 times daily, often combined with CJC-1295. | Phase 2 trial doses: 0.5 mg, 4 mg, 8 mg, and 12 mg weekly. The 12 mg dose produced maximum weight loss (28.7%). Phase 3 trials are evaluating doses up to 12 mg. Dose escalation schedule similar to other GLP-1s (start low, increase every 4 weeks). Final approved dosing not yet established — Phase 3 trials ongoing. |
| Administration | Subcutaneous injection. Best results when administered fasted or before sleep. Often stacked with GHRH peptides. | Subcutaneous injection, once weekly. Phase 3 trials use pre-filled single-dose pens. Not yet commercially available — estimated FDA approval ~2027-2028. |
| Side Effects | Generally well-tolerated. May cause mild headaches, lightheadedness, or increased hunger initially. | Phase 2 data: nausea (up to 25%), diarrhea (up to 22%), vomiting (up to 15%), constipation, decreased appetite. GI side effects were dose-dependent and generally mild-to-moderate. Lower rates of nausea compared to semaglutide, potentially due to GIP component. Increased heart rate observed at higher doses. |
| Best For |
Key Differences
Unique to Ipamorelin:
Unique to Retatrutide:
Key Studies
Ipamorelin
- The influence of ghrelin agonist ipamorelin acetate on the hypothalamic-pituitary-testicular axis in a cichlid fish, Oreochromis mossambicus.
Animal reproduction science, 2024
- The growth hormone secretagogue receptor 1a agonists, anamorelin and ipamorelin, inhibit cisplatin-induced weight loss in ferrets: Anamorelin also exhibits anti-emetic effects via a central mechanism.
Physiology & behavior, 2024
- Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients.
International journal of colorectal disease, 2014
Retatrutide
- Retatrutide in type 2 diabetes mellitus and obesity: an overview.
Expert review of clinical pharmacology, 2026
- Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials.
Diabetes, obesity & metabolism, 2026
- Rationale, design and baseline characteristics of the TRANSCEND-CKD trial of retatrutide in patients with chronic kidney disease.
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association, 2026
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