The short answer
In research peptide vendor listings, GLP-2 most commonly refers to tirzepatide and GLP-3 most commonly refers to retatrutide. But this is not a standardized naming convention; different vendors handle it differently. One vendor might list "GLP-2 T" without ever mentioning tirzepatide; the next vendor might list the same compound as "Tirzepatide" without any GLP numbering at all. Both are common.
The only reliable way to verify what you're actually looking at is to check the Certificate of Analysis (COA).
Why vendors use different names
There's no industry body that standardizes how research peptide vendors label their products. The GLP-1/2/3 shorthand developed organically as these compounds entered the market:
- GLP-1 = semaglutide, the first of the class to become widely known
- GLP-2 = tirzepatide (arrived second, with dual receptor action)
- GLP-3 = retatrutide (arrived third, with triple receptor action)
Some vendors adopted this shorthand; others stuck with compound names. You'll see both, often across different vendors selling the same product. Some vendors use a combination like "GLP-2 T," for example, where the T is shorthand for tirzepatide but the compound name itself never appears in the listing.
How to verify what you're actually buying
The Certificate of Analysis is your best tool. A COA from a third-party lab will identify the compound by name and confirm purity. If a vendor lists a product as "GLP-2" and the COA shows tirzepatide at the correct molecular weight and purity, that's a solid match. If the COA is missing, from an in-house lab only, or doesn't match what the listing implies; those are flags worth taking seriously regardless of what the product is called.
When you're comparing across vendors, don't assume the same label means the same compound. Check what each vendor's COA actually shows.
What GLP-1, GLP-2, and GLP-3 mean medically
A quick note for context, because this comes up: in pharmacology and medical literature, GLP-1, GLP-2, and GLP-3 refer to naturally occurring gut hormones (Glucagon-Like Peptides) that your body produces after eating. They're numbered as distinct biological molecules. GLP-2, for example, is actually a gut hormone involved in intestinal repair, and there's a drug called teduglutide (Gattex) that targets it for short bowel syndrome, completely unrelated to tirzepatide or weight loss.
The vendor shorthand borrows this numbering for a different purpose entirely. If you encounter "GLP-2" in a medical paper or clinical context, it likely means the gut hormone. If you encounter it on a vendor site, it almost certainly means tirzepatide. Context matters.
Quick reference
| Vendor Label | Usually Means | Verify Via |
|---|---|---|
| GLP-1 | Semaglutide | COA |
| GLP-2 | Tirzepatide | COA |
| GLP-3 | Retatrutide | COA |
Note that some vendors skip the GLP shorthand altogether and list compounds by their actual names (Tirzepatide, Retatrutide, Semaglutide). Either approach is valid: the COA is what matters.