The one-line difference
These three compounds get grouped together because they target the same family of metabolic pathways, but they are not the same molecule and they do not act the same way. The short version: semaglutide hits one receptor, tirzepatide hits two, and retatrutide hits three. Each added target is meant to push the metabolic effect further, and each one also adds complexity.
| Compound | Mechanism | Note |
|---|---|---|
| Semaglutide | Single agonist (GLP-1) | Most established human track record |
| Tirzepatide | Dual agonist (GLP-1 + GIP) | Adds a second incretin target |
| Retatrutide | Triple agonist (GLP-1 + GIP + glucagon) | Newest and most potent, least long-term data |
Research use only. The trial data described on this page refers to the pharmaceutical versions of these compounds studied in clinical settings. Nothing here is medical advice or a recommendation to use any of these compounds. We do not sell peptides; we track third-party vendor prices and per-batch lab data so you can compare honestly.
How they compare on weight
In clinical studies of the pharmaceutical versions, the pattern lines up with the mechanism. Retatrutide, the triple agonist, has produced the largest average weight reduction of the three. Tirzepatide has come in ahead of semaglutide. So on raw effect size, more receptor targets has tracked with more weight change.
Here is the honest caveat that gets skipped a lot: more potent also means less long-term human data. Semaglutide has been studied and used in people the longest, so its long-term safety picture is the most filled in. Retatrutide is the newest, and while early results look strong, there simply is not the same depth of long-term follow-up yet. A bigger short-term number is not the same as a more proven compound.
Side effects and titration
All three share the same general side effect profile, and it is mostly gastrointestinal. Nausea is the most commonly reported effect across the board, along with other GI effects that tend to show up when dosing moves too fast.
- Nausea is the most common complaint with all three compounds.
- Slow dose titration matters. All three are studied with a gradual ramp rather than starting high, which is generally how the GI effects are kept manageable.
- Retatrutide carries the most uncertainty. As the newest and most potent of the three, it has the least long-term human data, so its full tolerability and safety picture is the least complete.
The takeaway is not that one of these is clearly safer than another, it is that potency and proven track record pull in opposite directions here. If you read more on each compound, our semaglutide guide, tirzepatide guide, and retatrutide guide go deeper on each one individually.
Price per mg: where the value actually is
This is where the comparison gets interesting, because the strongest compound is not the cheapest. Below are the current median per-mg prices and the cheapest live listings we track across vendors. Prices move, so always check the live listing before you act.
| Compound | Median $/mg | Cheapest listings we track |
|---|---|---|
| Tirzepatide | $9/mg | Spartan Peptides $250 / 10 mg = $25/mg |
| Semaglutide | $10/mg | Onyx Biolabs $74.99 / 15 mg = $5/mg; Midwest Peptide $111.99 / 20 mg = $5.6/mg |
| Retatrutide | $9.3/mg | Onyx Biolabs $159.99 / 20 mg = $8/mg |
Per mg, tirzepatide is currently the best value of the three on the site. Its cheapest listing comes in much lower per mg than anything on the retatrutide or semaglutide side. Retatrutide costs the most per mg overall, which makes sense: it is the newest compound, so supply is tighter and listings carry a premium.
- See live listings on the tirzepatide page.
- See live listings on the semaglutide page.
- See live listings on the retatrutide page.
Which one for which goal
There is no single winner here, because the right pick depends on what you are weighing against what.
- If you value the longest track record: semaglutide has the most established human history of the three.
- If you want the best value per mg: tirzepatide is the standout, with the lowest cheapest-listing per-mg price we track.
- If you are following the largest average effect in trials: retatrutide led the three, but it is also the newest, the most expensive per mg, and the one with the least long-term data.
The honest framing: tirzepatide tends to sit in the middle as the balanced choice on data and price, semaglutide leans on its track record, and retatrutide is the high-ceiling, high-uncertainty option. Run all three through the compare tool with current prices before you decide.
Frequently asked.
Is retatrutide stronger than tirzepatide?
In clinical trials of the pharmaceutical versions, retatrutide produced the largest average weight reduction of the three, ahead of tirzepatide. It is a triple agonist (GLP-1 + GIP + glucagon) versus tirzepatide's dual action. The trade-off is that retatrutide is the newest compound and has the least long-term human data, so a larger short-term effect does not mean it is more proven.
Which is cheapest?
Per mg, tirzepatide is currently the best value of the three on the site. Its cheapest tracked listing works out to $3.17/mg, well below the cheapest retatrutide and semaglutide listings. Retatrutide costs the most per mg because it is the newest. Check the live listings, since prices change often.
Can you stack them?
We do not give dosing or stacking advice, and nothing here is medical advice. These compounds share overlapping mechanisms and the same GI side effect profile, so combining them is not something we recommend or describe protocols for. This page is for research-use comparison of how the compounds differ.
Is retatrutide approved?
No. As of 2026, retatrutide is still investigational and is not FDA-approved for general use. It is sold for research use only. The trial data discussed here refers to the pharmaceutical version studied in clinical settings.