Guide
Semaglutide vs tirzepatide vs retatrutide
Three incretin peptides, one, two and three receptors. How they differ by sequence, size and receptor target, and what tells them apart on a lab report.
Published September 4, 2026
Semaglutide binds one receptor, tirzepatide two, retatrutide three. That is the difference between them, and it is the one that matters when you are choosing. All three ship from pepuro with a Janoshik report on the vial.
| Peptide | Vial sizes | From |
|---|---|---|
| Semaglutide | 5mg, 10mg, 20mg, 30mg | $42.99 CAD |
| Tirzepatide | 5mg, 10mg, 15mg, 30mg, 40mg, 60mg | $42.99 CAD |
| Retatrutide | 5mg, 10mg, 20mg, 30mg, 40mg, 50mg | $53.99 CAD |
Free shipping across Canada. Every vial ships with a QR code linking to its own batch lab report. See all peptides
One, two, three receptors
Semaglutide is an acylated analog of human GLP-1(7-37). A C18 fatty-diacid chain hangs off the backbone and binds albumin, which is what extends its half-life in research models from minutes to days. It acts at one receptor: GLP-1.
Tirzepatide is a synthetic 39-residue peptide that binds two, the GIP receptor and the GLP-1 receptor. It is not a semaglutide derivative. It is a different sequence built to hit both.
Retatrutide adds a third. It is a triple agonist at GLP-1, GIP and the glucagon receptor, studied in metabolic and energy-balance models.
A vendor that calls one of these a version of another is wrong.
The masses, which is how you check
| Molecular weight | Receptors | Vial sizes we sell | |
|---|---|---|---|
| Semaglutide | 4113.58 g/mol | GLP-1 | 5, 10, 20, 30 mg |
| Retatrutide | 4731.32 g/mol | GLP-1, GIP, glucagon | 5, 10, 20, 30, 40, 50 mg |
| Tirzepatide | 4813.45 g/mol | GIP, GLP-1 | 5, 10, 15, 30, 40, 60 mg |
Seven hundred grams per mole separate the lightest from the heaviest. A mass-spec result on a real lab report reads to a fraction of that, so the observed mass tells you which of the three is in the vial without any trust required. If the observed mass on a report is not close to the expected figure, the identity check has failed, whatever the purity line says. How to read a peptide lab report works through a full certificate.
Same mass, different molecule count
All three are large peptides, so a 10 mg vial holds roughly two micromoles of any of them. But the numbers are not identical, and if your work is in molar units the difference matters:
| Vial | 1 mL | 2 mL | 3 mL | 5 mL |
|---|---|---|---|---|
| 5 mg | 5 mg/mL1.22 mM | 2.5 mg/mL0.608 mM | 1.67 mg/mL0.405 mM | 1 mg/mL0.243 mM |
| 10 mg | 10 mg/mL2.43 mM | 5 mg/mL1.22 mM | 3.33 mg/mL0.81 mM | 2 mg/mL0.486 mM |
| 20 mg | 20 mg/mL4.86 mM | 10 mg/mL2.43 mM | 6.67 mg/mL1.62 mM | 4 mg/mL0.972 mM |
| 30 mg | 30 mg/mL7.29 mM | 15 mg/mL3.65 mM | 10 mg/mL2.43 mM | 6 mg/mL1.46 mM |
Semaglutide vial sizes we sell, at four diluent volumes. Molarity uses 4113.58 g/mol. Other volumes
| Vial | 1 mL | 2 mL | 3 mL | 5 mL |
|---|---|---|---|---|
| 5 mg | 5 mg/mL1.04 mM | 2.5 mg/mL0.519 mM | 1.67 mg/mL0.346 mM | 1 mg/mL0.208 mM |
| 10 mg | 10 mg/mL2.08 mM | 5 mg/mL1.04 mM | 3.33 mg/mL0.693 mM | 2 mg/mL0.416 mM |
| 15 mg | 15 mg/mL3.12 mM | 7.5 mg/mL1.56 mM | 5 mg/mL1.04 mM | 3 mg/mL0.623 mM |
| 30 mg | 30 mg/mL6.23 mM | 15 mg/mL3.12 mM | 10 mg/mL2.08 mM | 6 mg/mL1.25 mM |
| 40 mg | 40 mg/mL8.31 mM | 20 mg/mL4.16 mM | 13.3 mg/mL2.77 mM | 8 mg/mL1.66 mM |
| 60 mg | 60 mg/mL12.5 mM | 30 mg/mL6.23 mM | 20 mg/mL4.16 mM | 12 mg/mL2.49 mM |
Tirzepatide vial sizes we sell, at four diluent volumes. Molarity uses 4813.45 g/mol. Other volumes
The reconstitution calculator has a preset page for each, with the molecular weight filled in.
What they have in common
All three ship as lyophilized powder, all three reconstitute the same way, and all three store the same way: freezer for the dry vial, fridge once it is in solution. How to reconstitute a lyophilized peptide covers the technique, which does not change between them.
Which one you have
One receptor is semaglutide, two is tirzepatide, three is retatrutide. The mass on the report tells you which is in the vial, and on a pepuro vial that report is one scan away.
For research use only. Not for human or animal consumption.
Frequently asked questions
What is the difference between semaglutide, tirzepatide and retatrutide?+
The number of receptors each one targets. Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual agonist at GIP and GLP-1. Retatrutide is a triple agonist at GLP-1, GIP and the glucagon receptor. They are three different molecules with three different sequences and masses.
Is retatrutide stronger than tirzepatide?+
That is not a question a supplier should answer. They act at different combinations of receptors, and comparative potency is a matter for the published research, not for a product page. What we can state is what each one binds and what each vial weighs.
Can I tell these three apart on a lab report?+
Yes, by mass. Semaglutide is about 4,113 g/mol, retatrutide about 4,731 and tirzepatide about 4,813. A mass-spec result matching one of those within a tenth of a percent identifies the molecule.
Which vial sizes do they come in?+
Semaglutide in 5 to 30 mg, tirzepatide in 5 to 60 mg, retatrutide in 5 to 50 mg. The table below has the live prices and the full ladder.
Related articles
- Semaglutide vs Retatrutide: one receptor or threeSemaglutide is a 31-residue GLP-1 analog. Retatrutide is a 39-residue triple agonist. 618 daltons and two receptors separate them.
- Semaglutide vs Tirzepatide: what is the difference?One receptor or two, 31 residues or 39, and a 700 dalton gap on the mass spec. How the two most-ordered GLP-1 research peptides differ, molecule by molecule.
- Tirzepatide vs Retatrutide: dual agonist or triple?Both are 39 residues with a C20 fatty chain. Retatrutide adds the glucagon receptor and drops 82 daltons. What separates them on paper and on a lab report.
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