Semaglutide vs Tirzepatide
vs Retatrutide
Three GLP peptides. Three different mechanisms. Wildly different results. Here's exactly how they compare — and which one is right for your goals.
Head-to-Head Breakdown
Mechanism, results, side effects, and best-fit use case for each peptide.
Semaglutide
Ozempic / Wegovy
Pros
- Most studied — 5+ years clinical data
- Lowest side-effect burden
- Easiest titration
- Potent appetite suppression
Cons
- Single receptor (GLP-1 only)
- Less fat loss than newer options
- Some muscle loss without resistance training
Best for
First-time GLP users, moderate fat loss goals
Tirzepatide
Mounjaro / Zepbound
Pros
- Dual mechanism — more pathways hit
- Better body composition vs semaglutide
- GIP action improves insulin sensitivity
- More fat loss at equivalent doses
Cons
- Less long-term data than semaglutide
- Slightly higher GI side-effect rate
- More expensive per mg
Best for
Serious fat loss + muscle preservation goals
Retatrutide
Research peptide (Phase 3)
Pros
- Highest fat loss of any peptide class
- Glucagon component boosts thermogenesis
- Better visceral fat clearance
- Preserves lean mass better than GLP-1 alone
Cons
- Newest — less clinical data
- More complex side-effect profile
- Heart rate elevation (monitor)
- Not yet FDA-approved (research use)
Best for
Maximum fat loss, refractory obesity, experienced users
Quick Comparison Table
| Factor | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Receptors targeted | GLP-1 | GLP-1 + GIP | GLP-1 + GIP + Glucagon |
| Fat loss (max dose) | 15–17% | 20–22% | 24–26% |
| Muscle preservation | Moderate | Good | Best |
| GI side effects | Moderate | Moderate–High | High |
| Clinical data | Extensive | Strong | Phase 3 trials |
| Best starting dose | 0.25mg/wk | 2.5mg/wk | 1mg/wk |
| Ideal for | Beginners | Intermediate | Advanced/aggressive |
The Advanced Play: Stack GLP + GH Peptides
GLP peptides excel at fat loss but carry lean mass loss risk. Stacking with CJC-1295/Ipamorelin (a GH secretagogue) counters this — GH actively builds and preserves muscle while the GLP burns fat. The result is true body recomposition rather than pure weight loss.
GLP Peptide FAQ
Which is stronger: semaglutide, tirzepatide, or retatrutide?+
For raw fat loss: retatrutide > tirzepatide > semaglutide. Retatrutide's triple agonist mechanism (GIP + GLP-1 + glucagon) produces the highest weight loss in trials — approximately 24–26% vs 20–22% for tirzepatide vs 15–17% for semaglutide at maximum doses. However, retatrutide also has the most complex side-effect profile and the least long-term data.
What is the difference between semaglutide and tirzepatide?+
Semaglutide targets only GLP-1 receptors. Tirzepatide targets both GLP-1 and GIP receptors simultaneously. The dual GIP/GLP-1 mechanism gives tirzepatide superior fat loss (20–22% vs 15–17% body weight) and better body composition outcomes, with similar or slightly higher GI side effects. Most users who have plateaued on semaglutide see renewed progress switching to tirzepatide.
Should I start with semaglutide or tirzepatide?+
For most first-time GLP users: start with semaglutide. It has the most clinical data, the most predictable titration protocol, and the lowest barrier to entry. If your results plateau at 12–16 weeks or your fat loss goals require more than 15% body weight reduction, transitioning to tirzepatide is a logical step up.
Is retatrutide available to buy?+
Retatrutide is currently in Phase 3 clinical trials. It is available as a research peptide through peptide suppliers. It is not FDA-approved as of 2026. Research use means it is not for human consumption per FDA guidelines, though it is widely used in the research community.
Do GLP peptides cause muscle loss?+
All GLP-class peptides carry some risk of lean mass loss alongside fat loss — this is the primary concern with this drug class. The key mitigation: (1) resistance training 3–4×/week, (2) high protein intake (1g+/lb bodyweight), (3) consider stacking with a GH secretagogue like CJC-1295/Ipamorelin to preserve or build muscle simultaneously. Retatrutide's glucagon component appears to reduce lean mass loss vs older GLP agents.
Can you stack semaglutide with CJC-1295/Ipamorelin?+
Yes — this is a popular combination. GLP peptides target fat loss through appetite suppression and metabolic rate, while CJC-1295/Ipamorelin boosts growth hormone to preserve and build lean muscle. The combination addresses the #1 risk of GLP-only protocols (muscle loss) and can produce significant body recomposition simultaneously.
Shop GLP Peptides
COA-verified semaglutide, tirzepatide, and retatrutide. US domestic shipping.