People searching for retatrutide often end up reading about tirzepatide, and the reverse. They are two different molecules from the same company, and they sit one receptor apart. This page lays out the difference, then shows what we found when we checked who sells each one.
The short version
Tirzepatide activates two receptors, GLP-1 and GIP. Retatrutide activates those two plus the glucagon receptor. Tirzepatide is an approved drug in the United States, sold by prescription as Mounjaro and Zepbound. Retatrutide is still in Eli Lilly's TRIUMPH trial program, and the vendor listing we read describes it as investigational and not FDA approved. Approval status can change, so check the sponsor's own pages before relying on this.
| Row | GLP-1 | GIP | Glucagon |
|---|---|---|---|
| Tirzepatide | Activates | Activates | Does not activate |
| Retatrutide | Activates | Activates | Activates |
- Activates
- Does not activate
As stated in the paragraph above. Retatrutide adds the glucagon receptor.
Side by side
Swipe the table sideways to see every column.
| Tirzepatide | Retatrutide | |
|---|---|---|
| Receptors activated | GLP-1 and GIP | GLP-1, GIP and glucagon |
| Status | FDA-approved drug (prescription) | Investigational, per the vendor listing |
| Molecular weight | 4,813.5 Da | About 4,731 Da |
| CAS number | 2023788-19-2 | 2381089-83-2 |
| Form and storage, per listing | Lyophilized powder, -20°C, away from light | Lyophilized powder, -20°C, away from light |
| Listing we checked | Core Power Peptides, 50 mg, $320 (marked down from $416) | Peptryn, 10, 30 and 60 mg, $130 to $320 |
| Lot report on the listing | None on the page we read | Two published, 99.62% (10 mg) and 99.32% (30 mg) |
What the extra receptor means
Glucagon is the third target, and it is the whole structural difference. A study built around a dual agonist tells you about two pathways. A triple agonist adds a third, so a result for one compound does not carry over to the other. If a protocol names retatrutide, tirzepatide is not a substitute, and the reverse is also true. Our guide on dual and triple agonist peptides covers the receptor biology in more detail.
Who sells which
Of the four vendors we review, three matter here. Core Power Peptides lists tirzepatide and does not list retatrutide. Peptryn lists retatrutide. American Peptides lists both (). This site briefly said no vendor we review carried retatrutide, and that was wrong; the correction is noted on the comparison page. Vendors list cagrilintide beside both compounds, and our cagrilintide peptide read covers it.
What the paperwork shows
Peptryn publishes two lot reports for retatrutide. The 10 mg lot dated 12 June 2026 reads 99.62% purity by HPLC-UV-MS with a negative endotoxin result. The 30 mg lot dated 31 August 2026 reads 99.32% purity with identity confirmed by mass spectrometry. Both were tested by MZ Biolabs, and the 60 mg size has a report available by email. We read the product page summary and have not read the full lab reports or contacted the lab.
The Core Power Peptides tirzepatide listing states 99% or higher purity and says independent labs test each batch. Its COA tab, when we checked, held a review widget and no certificate, and the listing says a certificate is available on request. Our Core Power Peptides review lists everything we could and could not confirm.
On paperwork alone Peptryn scores higher on our checklist, 6 of 6 against 4 of 6. The checks are explained in how to read a certificate of analysis.
Which one to look at
If your work calls for retatrutide, start with Peptryn's listing and its published lot reports. If it calls for tirzepatide, the listing we feature is at Core Power Peptides. We earn a commission on that one, which is why we also tell you where its paperwork falls short.
Frequently asked questions
Is retatrutide approved by the FDA?
Not according to the vendor listing we read, which calls it investigational. Eli Lilly is running it in the TRIUMPH program. Check the sponsor's own pages for the current status.
Can tirzepatide stand in for retatrutide in a protocol?
No. They activate a different number of receptors, so results for one do not transfer to the other.
Does Core Power Peptides sell retatrutide?
Not as of 29 September 2026. Peptryn does.
Are these sold for human use?
Vendors label them for research use only. Our guide to research-use-only labeling explains what that label does and does not cover. Nothing on this site is medical advice.