Retatrutide is the international nonproprietary name for LY3437943, an investigational peptide. This guide covers its structure, how its identity is confirmed in testing, and how to store it. It describes chemistry only, not effects in people or animals.
Structure
LY3437943 is a synthetic peptide of 39 amino acids, developed by Eli Lilly and Company. It has been studied as a single molecule that acts at three receptors: GIP, GLP-1 and glucagon.
Like other peptides in this family, it is not built only from the 20 standard amino acids. Its sequence includes non-standard residues such as α-aminoisobutyric acid (Aib), and a lysine side chain carries a fatty diacid attached through a linker. Its molecular formula is C221H342N46O68, with a molecular weight of about 4,731 g/mol.
How its identity is confirmed
Several peptides in this family look alike in a simple test. Janoshik’s “Common GLP-1 peptide blind test” compares the sample against reference standards for semaglutide, tirzepatide and retatrutide, so the report confirms which of the three is in the vial as well as how much of it there is, and its purity.
The current reports for our two sizes:
| Product | Retatrutide 15mg |
|---|---|
| Label | 15 mg |
| Measured: Retatrutide | 16.11 mg |
| Purity | 99.948% |
| Report | Janoshik #218225, analysed 11 Aug 2026 |
| Verification key | 6YMKXHA2U868 |
| Product | Retatrutide 30mg |
|---|---|
| Label | 30 mg |
| Measured: Retatrutide | 30.62 mg |
| Purity | 99.795% |
| Report | Janoshik #96881, analysed 07 Jan 2026 |
| Verification key | R3NDYIU7VZ6E |
Storage and handling
- Unopened, long term: −20 °C, protected from light.
- Unopened, short term: 2–8 °C for up to several weeks.
- Let the vial reach room temperature before opening, so moisture does not condense on the powder.
- After reconstitution: keep at 2–8 °C, avoid repeated freezing and thawing, and write the preparation date on the vial.
More detail in lyophilised peptides and storage, and a walk-through of every part of a report in how to read a peptide COA.
Available sizes
For laboratory research use only. LY3437943 is an investigational compound. It is not registered on the Australian Register of Therapeutic Goods, and nothing on this page describes use in humans or animals.
