Semaglutide vs Tirzepatide vs Retatrutide: The Plain-English Guide
Semaglutide, tirzepatide, retatrutide. They sound alike and they’re always mentioned together. Here’s the simplest possible way to tell them apart, plus what the GLP-2/Tirz and GLP-3/RT code names mean.
- Semaglutide targets one receptor (GLP-1), tirzepatide two (GLP-1 and GIP), and retatrutide three (GLP-1, GIP and glucagon).
- Semaglutide (Ozempic, Wegovy, Rybelsus) and tirzepatide (Mounjaro) are approved prescription medicines in Canada; retatrutide is still investigational as of 2026.
- Research suppliers sell these as laboratory compounds; Popular Peptides lists tirzepatide as GLP-2/Tirz ($44.99) and retatrutide as GLP-3/RT ($69.99), and does not stock semaglutide.
- Code names like GLP-2/Tirz and GLP-3/RT exist because of payment-processor rules, not because the molecule is different.
The quick version
Semaglutide, tirzepatide, retatrutide. You’ve heard all three names, probably from a news story, a friend, or your social feed. They sound alike and they’re always mentioned together, so it’s no wonder people mix them up.
Here’s the simplest way to remember them. Imagine a door with three locks:
- —Semaglutide opens one lock (GLP-1).
- —Tirzepatide opens two locks (GLP-1 and GIP).
- —Retatrutide opens all three (GLP-1, GIP and glucagon).
That’s the whole difference in one picture. The rest of this page fills in the details.
Side by side
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptors (the “locks”) | 1: GLP-1 | 2: GLP-1 + GIP | 3: GLP-1 + GIP + glucagon |
| Nickname | “Sema” | “Tirz” | “Reta” |
| Developed by | Novo Nordisk | Eli Lilly | Eli Lilly |
| Prescription brands | Ozempic, Wegovy, Rybelsus | Mounjaro, Zepbound | None yet (investigational) |
| Research compound at Popular Peptides | Not stocked | GLP-2/Tirz 10mg, $44.99 | GLP-3/RT 10mg, $69.99 |
The one thing everyone should know first
Two of these three are the active ingredients in real prescription medicines. If you’re hoping to use one for your own health, that’s a conversation for your doctor or pharmacist. It genuinely is the better path: they’ll look at your whole picture and you’ll get a regulated product.
What research suppliers like us sell is the compound itself, as a freeze-dried powder for laboratory work. Same molecule on paper, completely different world. Once you understand that, the internet gets a lot less confusing.
Semaglutide, the “one lock” compound
Semaglutide was the first of the three to become a household name. It mimics GLP-1, a natural hormone your gut releases after you eat. It’s been studied more than the other two combined, simply because it’s been around longest.
We don’t stock semaglutide right now. If you’re researching the GLP-1 family, most researchers are now looking at the newer multi-receptor compounds below.
Tirzepatide, the “two lock” compound
Tirzepatide added a second target, GIP, another gut hormone. That dual action is what made it such big news. On our site it’s GLP-2/Tirz, and we wrote a full tirzepatide buying guide for Canadians. The published trial results are summarized in our tirzepatide trial data article.
Retatrutide, the “three lock” compound
Retatrutide adds a third target, the glucagon receptor. It’s the newest of the three and still in clinical trials as of 2026, which is why there’s no prescription brand yet and why it’s one of the most searched research peptides in Canada. On our site it’s GLP-3/RT. See our retatrutide buying guide and the phase 3 trial data.
Why the code names?
You’ll notice many Canadian shops don’t print “tirzepatide” or “retatrutide” on their product pages. That’s because of payment-processor rules around certain compound names, not because the product is different. GLP-2/Tirz is tirzepatide. GLP-3/RT is retatrutide.
And what’s cagrilintide?
It keeps showing up next to these three, so here’s a quick note. Cagrilintide works on a different system altogether: amylin, a hormone released alongside insulin. Researchers often study it together with GLP-1 compounds. We stock it as a 10mg research vial.
Buying any of these in Canada: three rules
- —Buy from a shop that ships from inside Canada. These are exactly the parcels most likely to be held at the border. Our Canada vs imported guide explains why.
- —Insist on a lab report for your exact batch, with a matching lot number and an identity test. Our COA guide shows you how to read one.
- —Compare prices in CAD, for the same milligrams.
Frequently asked questions
What is the difference between semaglutide, tirzepatide and retatrutide?
They act on different numbers of receptors. Semaglutide targets GLP-1. Tirzepatide targets GLP-1 and GIP. Retatrutide targets GLP-1, GIP and glucagon, which is why it’s called a triple agonist.
Is retatrutide stronger than tirzepatide?
Retatrutide acts on one more receptor than tirzepatide. How that plays out is still being studied in clinical trials, and retatrutide is not yet an approved medicine. Our retatrutide phase 3 article summarizes the published data.
Which of these are approved in Canada?
Semaglutide (Ozempic, Wegovy, Rybelsus) and tirzepatide (Mounjaro) are approved prescription medicines in Canada. Retatrutide is still investigational as of 2026.
What is GLP-3/RT?
GLP-3/RT is the name Popular Peptides uses for retatrutide, sold as a 10mg research compound for $69.99 CAD.
What is GLP-2/Tirz?
GLP-2/Tirz is the name Popular Peptides uses for tirzepatide, sold as a 10mg research compound for $44.99 CAD.
Does Popular Peptides sell semaglutide?
Not currently. Popular Peptides stocks GLP-2/Tirz (tirzepatide), GLP-3/RT (retatrutide) and cagrilintide as research compounds.
Where to go next
- —GLP-3/RT (retatrutide) 10mg
- —GLP-2/Tirz (tirzepatide) 10mg
- —Cagrilintide 10mg
- —New to all of this? Our Start Here guide is a friendly place to begin.
Sold for laboratory research use only. Not for human consumption. Nothing here is medical advice.
Every batch we sell is independently third-party tested, with the full Certificate of Analysis published and checkable by lot number.