The answer, first. Both are approved and both have completed phase 3 programmes, which puts this pair in a different category from almost everything else in our index. The honest comparison is therefore not about evidence quality — both clear the bar — but about mechanism and about what the trials actually measured.
Side by side
The same two axes this site applies to every compound, with nothing added for the comparison.
| Semaglutide | Tirzepatide | |
|---|---|---|
| Clinical evidence | approved | approved |
| Community adoption | very high | very high |
| Category | weight loss | weight loss |
| Our summary | A GLP-1 receptor agonist, FDA-approved as Ozempic for type 2 diabetes and Wegovy for weight management. One of the most thoroughly trialed compounds on this index. | A dual GLP-1 and GIP receptor agonist, FDA-approved as Mounjaro for type 2 diabetes and Zepbound for weight management. The benchmark the rest of the class is measured against. |
| Full file | Semaglutide → | Tirzepatide → |
What actually separates them
Three differences that hold up against the published record, rather than against marketing.
What neither can tell you
- What is in the vial. A comparison between molecules says nothing about the contents of a specific lot. Only a certificate of analysis does, and most cover fewer measures than buyers assume — start with how to read a COA.
- A dose. This site describes what published protocols used and never prescribes.
- Which is right for you. That is a clinical question about an individual, and nothing here is medical advice.
Questions we get
Which is better, semaglutide or tirzepatide?
Both are approved with completed phase 3 evidence, so neither is an evidence gap — which is unusual in this index. They differ in mechanism: semaglutide is a GLP-1 agonist and tirzepatide is a dual GIP/GLP-1 agonist. Comparing them is a clinical question about an individual, and this site does not give medical advice or make individual recommendations.
Do both carry the same lean-mass trade-off?
The lean-mass question applies to GLP-1 agonists as a class. Our report covers what the DXA substudy data actually describes and what it does not, along with the training and protein counterweights that the headline percentage cannot speak to.
Does an approval mean a research vial is safe?
No. An approval attaches to a manufactured product made under regulated conditions. A research-market vial of the same molecule is a different object, and only a certificate of analysis for that lot speaks to what is in it.