Retatrutide vs tirzepatide

Two generations of the same idea

Both peptides come from Eli Lilly and Company, and both start from the same idea: one molecule that acts on more than one gut-hormone receptor. Tirzepatide is a dual agonist at the GIP and GLP-1 receptors. Retatrutide adds a third target, the glucagon receptor, which makes it a triple agonist.

Structurally they are close relatives. Each is a synthetic peptide of around 39 amino acids built on a GIP-based backbone, with a fatty diacid side chain that binds albumin and extends half-life in pharmacology studies. The differences lie in a handful of amino-acid substitutions, which change how strongly each molecule activates each receptor.

The three receptors

• GLP-1 receptor: the target of the first incretin-based medicines. It is studied for its roles in glucose-dependent insulin secretion, glucagon suppression, gastric emptying and appetite signalling in the brain.
• GIP receptor: the other incretin receptor. Its role was debated for years; tirzepatide's results renewed interest in combining it with GLP-1 activity. It is studied in pancreatic, adipose-tissue and central nervous system models.
• Glucagon receptor: found mainly in the liver. Glucagon raises glucose output, but in preclinical models its receptor has also been studied for effects on energy expenditure and hepatic lipid metabolism. This is the receptor that retatrutide adds.

Side by side

What the trials compared

There is no published head-to-head trial of retatrutide against tirzepatide, so any comparison of trial outcomes is indirect. Different trials enrolled different populations, ran for different lengths of time and used different study designs, which limits what can be read across from one programme to another.

Tirzepatide's evidence base is much larger. The SURPASS trials in type 2 diabetes and the SURMOUNT trials in obesity and overweight enrolled thousands of participants, and their results underpin the approved medicines. Retatrutide's published human data so far come mainly from two phase 2 trials in 2023, one in obesity (New England Journal of Medicine) and one in type 2 diabetes (The Lancet). The TRIUMPH phase 3 trials are designed to test those early findings in larger and more varied populations, and results are being reported by the sponsor in stages.

In the published trials of both compounds, gastrointestinal events were the most commonly reported adverse events. Retatrutide's papers also discuss heart-rate increases, a known topic for the glucagon receptor class. Researchers should read each paper's safety data in full.

Why researchers study one or the other

For a lab, the choice usually follows the question being asked. Tirzepatide is the reference dual incretin agonist, with a large body of published pharmacology to compare against. Retatrutide is used where the glucagon receptor is part of the question, for example in models of energy expenditure or hepatic metabolism, or where a study compares dual and triple agonism directly.

Both are supplied the same way for research: lyophilised powder in a sealed vial, labelled by peptide content. Identity and purity testing are equally important for both; retatrutide's newer synthesis makes a batch certificate of analysis especially worth checking. Every vial Friday stocks is lab-tested by batch, and we can share a batch's report on request.

Buying either from Friday

Tirzepatide is listed from ฿1,890 and retatrutide from ฿3,190, both on the shop. Orders are packed in Bangkok and leave with tracking the next working day, to any address in Thailand. Delivery is a flat ฿60, prices are in Thai baht, and payment is by bank transfer with a slip that our team confirms before dispatch.

Read the single-compound guides for more detail: tirzepatide in Thailand and retatrutide in Thailand.