Tirzepatide vs. Retatrutide: a sourcing comparison

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.