GLP-1, GLP-2, and “GLP-3”: what the terms actually mean.

GLP-1 and GLP-2 are established scientific terms, but they describe different peptides and biological roles. They are not numbered generations of the same product category.

“GLP-3” is not a formal human peptide classification. It is sometimes used informally for triple-agonist research, including retatrutide, whose receptor targets are GIP, GLP-1, and glucagon.

GLP-1 means glucagon-like peptide-1. Research on this pathway includes GLP-1 receptor agonism and broader incretin biology.

That does not mean every GLP-related compound is the same. Semaglutide is generally discussed as a GLP-1 receptor agonist, tirzepatide as a dual GIP/GLP-1 receptor agonist, and retatrutide as a triple hormone receptor agonist involving GIP, GLP-1, and glucagon receptors.

• Compare compounds by their exact names and receptor targets.
• Use the product-specific research notes to review evidence stage and citations.
• Do not treat all GLP-related compounds as interchangeable.

Formally, GLP-2 means glucagon-like peptide-2, a 33-amino-acid proglucagon-derived peptide mainly associated with intestinal biology. That is separate from the internet habit of calling second-generation dual-incretin products GLP-2.

Some informal comparisons use GLP-2 to mean a two-pathway product, but that conflicts with the established peptide name. Tirzepatide is more precisely described by its dual GIP and GLP-1 receptor activity.

Lilly describes “GLP-3” as a scientifically inaccurate informal label for triple hormone receptor agonists. The term does not identify a recognized human peptide category.

Retatrutide is more precisely described as a triple agonist because one molecule activates GIP, GLP-1, and glucagon receptors.

GLP-1 is an established incretin term. GLP-2 is a different, formally recognized peptide. “GLP-3” is informal shorthand rather than an official human peptide label.

When comparing research products, use the exact compound name, receptor targets, available size, and product-specific research note. Research Chem Co products are offered only for laboratory research use.