You've seen it by now. A vendor listing that just says "GLP-2," no compound name anywhere on the page, like you're supposed to already be in on it. You're not being dense. Nobody agreed on this, and it's one of the most common points of confusion for women comparing tirzepatide and retatrutide across vendors while trying to figure out what they're actually paying for.
Here's the short version, and then the part that actually matters. GLP-2 almost always means tirzepatide. GLP-3 almost always means retatrutide. But "almost always" is doing real work in that sentence, and the only way to close the gap between "almost" and "actually" is the Certificate of Analysis.
Why this shorthand even exists
Nobody standardized it. No lab, no board, no industry group sat down and decided GLP-2 would mean tirzepatide. The numbering just grew out of the order these compounds showed up. Semaglutide came first, so it inherited the GLP-1 label everyone already knew from the approved drug. Tirzepatide came next with a second receptor added, so vendors started calling it GLP-2. Retatrutide showed up with a third receptor, and GLP-3 followed the same logic.
It's a nickname that stuck, not a spec. Some vendors run with it and never mention the actual compound name anywhere on the listing. Others skip the shorthand entirely and just write "Tirzepatide" like a normal label. You'll see a vendor use "GLP-2 T," where the T quietly does the work of telling you it's tirzepatide, sitting right next to a competitor selling the identical compound under its real name. Same molecule, two completely different labels, zero explanation either way.
How to actually check what you're buying
Skip the guessing and go straight to the Certificate of Analysis (COA). A COA from a real third-party lab identifies the compound by name and confirms its purity, and that's the one document a vendor can't fudge with clever labeling. If the listing says "GLP-2" and the COA shows tirzepatide at the right molecular weight and purity, you're looking at the real thing. If the COA is missing, comes only from an in-house lab, or doesn't line up with what the listing implies, that's worth taking seriously no matter what the product is called.
This matters more than the naming convention itself. Don't assume two vendors using the same label are selling the same thing. Pull up each one's COA and compare.
One more wrinkle: this isn't the medical meaning
Quick honest aside, because it trips people up. In actual pharmacology, GLP-1, GLP-2, and GLP-3 are three separate gut hormones your body makes on its own, numbered because they're distinct molecules, not because one is a stronger version of another. GLP-2 in a medical journal refers to a hormone involved in intestinal repair, and there's an FDA-approved drug called teduglutide (Gattex) that targets it for short bowel syndrome. It has nothing to do with tirzepatide or weight loss.
The vendor shorthand borrowed the numbers for a completely unrelated purpose. If you're reading a clinical paper, GLP-2 means the gut hormone. If you're reading a vendor listing, it almost certainly means tirzepatide. Same three characters, two different worlds. Context is everything here.
Quick reference
| Vendor Label | Usually Means | Verify Via |
|---|---|---|
| GLP-1 | Semaglutide | COA |
| GLP-2 | Tirzepatide | COA |
| GLP-3 | Retatrutide | COA |
Plenty of vendors skip the shorthand entirely and just list the real compound name. That's fine too. Either way, the COA is what actually tells you what's in the vial, not the label on the front of it.