What is the difference between semaglutide and tirzepatide?

Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a dual GLP-1 and GIP receptor agonist. Retatrutide adds a third mechanism (glucagon receptor). In clinical trials, tirzepatide showed greater weight loss than semaglutide at equivalent doses.

What is retatrutide and how does it compare to semaglutide?

Retatrutide (GLP-3) is a triple agonist activating GLP-1, GIP, and glucagon receptors simultaneously. Research suggests it produces greater metabolic effects than either semaglutide or tirzepatide, though it is newer and currently priced higher at $4.50/mg+.

PepsTracker › GLP-1 Comparison

⚗️ Research Comparison

Semaglutide vs Tirzepatide vs Retatrutide — June 2026

Q: What is cheaper — semaglutide or tirzepatide?

Tirzepatide is generally cheaper per mg than semaglutide. The cheapest tirzepatide in 2026 starts from $3.09/mg vs semaglutide from $2.75/mg. However, tirzepatide is a dual GIP/GLP-1 agonist considered more potent, so the cost per effective dose may differ.

Last updated: June 2026 · Prices from 15 vendors · Updated daily

📊 Quick Price Summary

$2.75/mg

Semaglutide
Compare →

$3.09/mg

Tirzepatide
Compare →

$4.50/mg

Retatrutide
Compare →

Mechanism of Action

Semaglutide (GLP-1)

Semaglutide is a GLP-1 receptor agonist — it mimics the glucagon-like peptide-1 hormone, which is naturally released after eating. It slows gastric emptying, reduces appetite signaling in the brain, and stimulates insulin secretion. Research grade only.

Tirzepatide (GLP-1 + GIP)

Tirzepatide is a "twincretin" — it activates both GLP-1 and GIP receptors. GIP (glucose-dependent insulinotropic polypeptide) adds complementary metabolic effects including fat cell remodeling. Phase 3 research showed greater metabolic effects than semaglutide alone.

Retatrutide (GLP-1 + GIP + Glucagon)

Retatrutide adds glucagon receptor agonism to the dual GIP/GLP-1 mechanism of tirzepatide. Glucagon receptor activation increases energy expenditure. Currently the most potent metabolic peptide in research, though data is still emerging.

Price Comparison — June 2026

Peptide	Best $/mg	Mechanism	Compare
Semaglutide	$2.75/mg	GLP-1	All vendors →
Tirzepatide	$3.09/mg	GLP-1 + GIP	All vendors →
Retatrutide	$4.50/mg	GLP-1 + GIP + GCG	All vendors →

❓ Frequently Asked Questions

What is cheaper — semaglutide or tirzepatide for research?

Semaglutide is currently cheaper at $2.75/mg vs tirzepatide at $3.09/mg. However tirzepatide activates two receptor pathways (GLP-1 and GIP) vs semaglutide's one. Compare all current vendor prices on our dedicated comparison pages.

Which is more studied — semaglutide, tirzepatide, or retatrutide?

Semaglutide has the longest research history. Tirzepatide has completed major Phase 3 trials. Retatrutide is newest — Phase 2 data was released in 2023, Phase 3 trials are ongoing. All are sold for research use only.

Where can I find current peptide prices?

PepsTracker tracks prices daily across 15 vendors. See our comparison pages: Cheapest Semaglutide, Cheapest Tirzepatide, Cheapest Retatrutide.