Semaglutide vs Tirzepatide: Two GLP-1 Pathways Compared

Both compounds activate the GLP-1 receptor — that’s where the similarity ends. One is a single-receptor agonist; the other adds a second pathway. Here’s how that changes the research picture.

The mechanistic split

Property	Semaglutide	Tirzepatide
Receptor targets	GLP-1	GIP + GLP-1
Reported half-life	≈ 7 days	≈ 5 days
Vial size	5 mg lyophilized	10 mg lyophilized
Molecular weight	≈ 4,114 g/mol	≈ 4,813 g/mol

Semaglutide is a long-acting GLP-1 receptor agonist — a common reference standard in receptor binding assays. Tirzepatide is the dual GIP/GLP-1 agonist, and the GIP component is exactly what researchers cite when comparing the two: it adds a second incretin pathway to study, which is why tirzepatide protocols show up in glucose-homeostasis and incretin-signaling work that semaglutide alone doesn’t cover.

Vial math differs — don’t mix them up

• Semaglutide 5 mg = 5,000 µg. With 2 mL water: 2,500 µg/mL, so a 250 µg dose is 10 units.
• Tirzepatide 10 mg = 10,000 µg. With 2 mL water: 5,000 µg/mL, so a 2,500 µg dose is 50 units.

The semaglutide calculator and tirzepatide calculator handle each vial’s math with their reference titration tables — worth checking before a protocol, because the 5 vs 10 mg difference is an easy slip.

Practical notes

Both store lyophilized at −20 °C and reconstitute with USP bacteriostatic water. Full specs: Semaglutide and Tirzepatide. For the triple-agonist alternative, see Retatrutide vs Tirzepatide.

For laboratory research use only. Not medical advice.