GLP-1 · Comparison
Tirzepatide vs retatrutide: what the trials actually show
Retatrutide (Eli Lilly's triple agonist: GLP-1 + GIP + glucagon) produced 24.2% weight loss in Phase 2 — the largest of any weight-loss drug tested. Tirzepatide (dual GLP-1/GIP) is already FDA-approved and delivers ~22%. Here's how they actually compare and which one you can get.
Head-to-head weight loss
| Drug | Trial | Avg loss |
|---|---|---|
| Semaglutide 2.4 mg | STEP-1 | 14.9% |
| Tirzepatide 15 mg | SURMOUNT-1 | 22.5% |
| Retatrutide 12 mg | Phase 2 (2023) | 24.2% |
Mechanism
- Tirzepatide — dual GLP-1 + GIP agonist
- Retatrutide — triple GLP-1 + GIP + glucagon agonist (adds fat oxidation via glucagon)
Availability
Tirzepatide: FDA-approved (Zepbound for weight loss, Mounjaro for diabetes). Available now.
Retatrutide: Investigational. Phase 3 TRIUMPH trials ongoing.
Practical recommendation
Start with tirzepatide now if you're a candidate. If retatrutide receives FDA approval and clinical trials continue to support superiority, transitioning is straightforward. See our GLP-1 for menopause guide.
Frequently asked questions
Is retatrutide better than tirzepatide?
In Phase 2 data, yes on weight loss: 24.2% vs ~22%. Retatrutide is not FDA-approved yet, so tirzepatide is the strongest option legally available in 2026.
Can I get retatrutide legally in 2026?
Only through clinical trials. It is not FDA-approved and not on the FDA compounding list, so no US pharmacy can legally dispense it. See <a href="/how-to-get-retatrutide">how to get retatrutide</a>.
What is the difference between GLP-1, GIP, and glucagon receptors?
GLP-1: appetite and insulin. GIP: insulin secretion, some appetite. Glucagon: energy expenditure and fat oxidation. Tirzepatide hits the first two; retatrutide hits all three.
Does retatrutide have more side effects?
Phase 2 GI side effects were similar to semaglutide and tirzepatide — nausea, constipation, diarrhea, mostly mild-to-moderate and titration-related.
Should I wait for retatrutide or start tirzepatide?
Do not wait. Approval is expected 2026-2027 but not guaranteed. Every year of untreated obesity increases cardiometabolic risk. Start with FDA-approved options now; switch if retatrutide launches and clinically appropriate.
Considering a physician-supervised longevity protocol? Kindr Health evaluates peptide therapy as part of personalized perimenopause and menopause care.
Request your Longevity Consult →Related: FDA peptide review July 2026 briefing · Peptide therapy hub · Longevity service
Medically reviewed by Kindr Health Clinical Team · Last reviewed 2026-06-19. Compounded medications are prepared by FDA-registered 503A pharmacies and are not FDA-approved drug products.