📑 Contents
Overview: Three Generations of Weight Loss Peptides
The market for GLP-1-based peptides is rapidly evolving. Here are the three main options:
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Manufacturer | Novo Nordisk | Eli Lilly | Eli Lilly |
| Receptors | GLP-1 | GLP-1 + GIP | GLP-1 + GIP + Glucagon |
| Approved | ✓ Yes | ✓ Yes | Phase 3 ongoing |
| Brands | Ozempic, Wegovy | Mounjaro, Zepbound | — |
Effectiveness: Weight Loss
The key question — which delivers the best results?
💊 Semaglutide (STEP Studies)
- Weight Loss: 15-17% over 68 weeks
- Extensively documented with thousands of study participants
- Consistent results across multiple studies
💊 Tirzepatide (SURMOUNT Studies)
- Weight Loss: 20-22% over 72 weeks
- Highest dose (15 mg) achieved up to 25% in some
- Significantly better than Semaglutide in direct comparisons
💊 Retatrutide (Phase 2 Study)
- Weight Loss: 24.2% over 48 weeks
- Some participants lost up to 30%!
- Phase 3 data expected in 2025
🏆 Winner: Effectiveness
Retatrutide — based on available data, with the caveat that phase 3 results have not yet been published.
Mechanism of Action
Semaglutide: Single Agonist
Activates only the GLP-1 receptor:
- Reduces appetite via the brain
- Slows gastric emptying
- Improves insulin release
Tirzepatide: Dual Agonist
Activates GLP-1 + GIP:
- All effects of GLP-1
- PLUS improved insulin sensitivity via GIP
- Potentially better for diabetics
Retatrutide: Triple Agonist
Activates GLP-1 + GIP + Glucagon:
- All effects of GLP-1 and GIP
- PLUS increased fat burning via the glucagon receptor
- Higher resting energy expenditure
- Potentially better preservation of muscle mass
Side Effect Profile
⚠️ Common Side Effects (all three)
- Nausea
- Diarrhea
- Constipation
- Vomiting
- Abdominal pain
Differences in Frequency
| Side Effect | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Nausea | ~40% | ~35% | ~35% |
| Diarrhea | ~30% | ~25% | ~25% |
| Constipation | ~25% | ~20% | ~20% |
Overall, Tirzepatide and Retatrutide appear to have a slightly lower frequency of gastrointestinal side effects, possibly due to the GIP component.
📖 Learn more about side effects →
Dosage Comparison
| Peptide | Starting Dose | Maintenance Dose | Titration |
|---|---|---|---|
| Semaglutide | 0.25 mg/week | 1.0-2.4 mg/week | 16+ weeks |
| Tirzepatide | 2.5 mg/week | 5-15 mg/week | 20+ weeks |
| Retatrutide | 1 mg/week | 8-12 mg/week | 24+ weeks |
📖 See detailed dosage schedule →
Availability and Status
Who is Suitable for Which?
💡 Choose Semaglutide if you:
- Are new to GLP-1 peptides
- Want the most well-established treatment
- Prioritize safety data
- Have type 2 diabetes (Ozempic approved for this)
💡 Choose Tirzepatide if you:
- Did not achieve sufficient effect with Semaglutide
- Want better blood sugar control
- Are ready for a more potent option
🚀 Choose Retatrutide if you:
- Want maximum weight loss effect
- Are comfortable with research peptides
- Accept that long-term data is lacking
- Are interested in cutting-edge development
Price Comparison
Approximate costs for prescription medications in Sweden:
| Peptide | Monthly Cost (prescription) |
|---|---|
| Semaglutide (Wegovy) | ~2000-3000 SEK |
| Tirzepatide (Zepbound) | ~2500-3500 SEK |
| Retatrutide | Not available on prescription |
Research peptides generally have lower costs.
Summary
| Category | Best Choice |
|---|---|
| Most Effective | Retatrutide |
| Most Proven | Semaglutide |
| Best for Diabetes | Tirzepatide |
| Most Accessible | Semaglutide |
| Least Side Effects | Tirzepatide/Retatrutide |
✓ Conclusion
All three are effective options. The choice depends on your individual goals, tolerance, and comfort with new vs established treatments.