Tirzepatide vs. Retatrutide: a sourcing comparison
Side-by-side on regulatory status, sourcing complexity, vial-size availability, and how to choose between the two for your compounding pipeline.
Published May 8, 2026 · 8 min read · By PeptideXpo Regulatory Team
Tirzepatide (GIP / GLP-1) and Retatrutide (GIP / GLP-1 / glucagon) are the two most-requested GLP-1-family peptides at our sales desk. For buyers building a metabolic-research portfolio, the differences matter at three levels: chemistry, regulatory, and supply economics.
Chemistry
- Tirzepatide is a 39-amino-acid GIP/GLP-1 co-agonist. CAS 2023788-19-2. Molecular weight ~4814 g/mol.
- Retatrutide is a 39-amino-acid tri-agonist targeting GIP, GLP-1, and glucagon receptors. CAS 2381089-83-2.
Both are typically supplied as lyophilized acetate salts and require -20 °C storage with light protection.
Regulatory
Tirzepatide is FDA-approved as a finished drug under the brand Mounjaro / Zepbound. Retatrutide is an investigational compound currently in clinical development.
For compounding pharmacy use, neither is currently on the 503A bulks list. Both ship from PeptideXpo as research-grade material for buyers in jurisdictions where commercial use is permitted.
Supply economics
- Tirzepatide vial flexibility is the broadest in our catalog: 2 mg to 120 mg single-vial fills.
- Retatrutide is supplied in 5 mg to 60 mg fills with a slightly longer lead time (10-18 days vs. 7-14 days).
- Bulk pricing for Retatrutide currently runs higher per-mg than Tirzepatide due to lower aggregate production volumes.
How to choose
If your protocol is anchored on GIP/GLP-1 co-agonism and you need vial-size optionality, Tirzepatide is the more practical choice today. If your research is targeting tri-agonism and downstream glucagon-axis biology, Retatrutide is the obvious answer despite the supply premium.
In either case, request a sample COA before committing to scale, both compounds vary substantially between suppliers, and the analytical packet is the first place differences surface.
Frequently asked questions
- What is the difference between Tirzepatide and Retatrutide?
- Tirzepatide (CAS 2023788-19-2, ~4814 g/mol) is a 39-amino-acid GIP / GLP-1 dual co-agonist; Retatrutide (CAS 2381089-83-2) is a 39-amino-acid tri-agonist that adds glucagon-receptor (GCGR) activity on top of GIP and GLP-1. The extra glucagon arm is the main pharmacological distinction. Tirzepatide is FDA-approved as a finished drug (Mounjaro / Zepbound); Retatrutide is still investigational.
- Which has broader vial-size and supply availability, Tirzepatide or Retatrutide?
- Tirzepatide has the broader supply: 2 mg to 120 mg single-vial fills and a 7-14 day lead time. Retatrutide ships in 5 mg to 60 mg fills with a 10-18 day lead time, and bulk per-mg pricing runs higher because aggregate production volumes are lower. For vial-size optionality today, Tirzepatide is the more practical choice.
- Are Tirzepatide and Retatrutide on the 503A bulks list for compounding?
- Neither is currently on the 503A bulks list. PeptideXpo supplies both as research-grade material for buyers in jurisdictions where commercial use is permitted; compounding eligibility depends on the destination market's current regulatory posture, which buyers are responsible for verifying. Request a sample COA before scaling, since both compounds vary substantially between suppliers.