GLP-1
Reta vs Tirz vs Sema: which GLP-1 actually fits you
Three very different molecules that all get called “the weight-loss peptide.” Here is how I’d pick between them.
The quick version
- Weight loss in trials: semaglutide ~15%, tirzepatide ~20%, retatrutide ~24%.
- More receptors, from sema to tirz to reta, means more effect but less long-term data.
- New and cautious: sema. Want more: tirz. Experienced, chasing the most: reta.
Three molecules, one nickname. Semaglutide, tirzepatide, and retatrutide all get called “the weight-loss peptide,” but they’re different tools. The real answer to “which one?” is “it depends on you.” Here’s how I think it through. Not a doctor, not medical advice.
The one-line version of each
Semaglutide: a single GLP-1 agonist. One receptor, the most track record, quiets appetite.
Tirzepatide: a dual agonist (GLP-1 + GIP). Adding GIP tends to improve results and smooth the nausea. The step up.
Retatrutide: the triple (GLP-1 + GIP + glucagon). The third receptor nudges metabolic rate, which is why the numbers are eye-catching. Also the newest, with the least long-term data. (Full write-up here.)
Side by side
Ballpark from the published trials, not a promise. Real results swing with diet, training, dose, and genetics.
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptors | GLP-1 | GLP-1 + GIP | GLP-1 + GIP + glucagon |
| Track record | Most established | Strong, newer | Newest, Phase 2/3 stage |
| Typical loss (trials) | ~15% | ~20% | ~24% (Phase 2) |
| Dosing | Weekly | Weekly | Weekly |
| Nausea reputation | Most noticeable | Often gentler than sema | Manageable if you ramp slow |
How I’d actually choose
- Brand new and cautious? Semaglutide. Most studied, most predictable, easiest to find good information on.
- Want more, or hated the nausea? Tirzepatide. The GIP component is why people who struggled on sema often do better here.
- Experienced, chasing the strongest effect? Retatrutide. Go in clear-eyed that it’s the newest, and respect the slow titration.
The part most comparisons skip
Every one of these only works if what’s in the vial is real and correctly dosed. A “stronger” compound from a sketchy source loses to a “weaker” one from a clean source every time. So before you agonize over reta-versus-tirz, settle the question that moves the needle: who are you buying from, and can they prove it?
Bottom line
Semaglutide for the surest footing, tirzepatide for the upgrade or the nausea-sensitive, retatrutide for the experienced who accept the newness. Then do the unglamorous fundamentals, and sort out your source first.
Reminder: I’m not a doctor and this isn’t medical advice, it’s my own notes and reading of the research. Peptides sit in a legal grey area; research-grade is a real category, and it’s on you to verify your own compliance. Talk to a qualified professional before you start anything, especially if you’re on other medication.