Semaglutide vs Retatrutide: Comparing Two GLP-1s in Canada | Prescott Bio

Prescott Bio Editorial · ·
  • semaglutide
  • retatrutide
  • glp-1
  • canada

Key takeaways

  • Semaglutide is a GLP-1 receptor agonist. Retatrutide is a triple agonist that also hits GIP and glucagon receptors.
  • Both are lyophilized peptides sold in vial sizes measured in milligrams.
  • This guide compares them mechanically and from a sourcing angle only — no dosing or use-case guidance.

Semaglutide and retatrutide are both GLP-1-family compounds that Canadian buyers frequently ask about. This guide walks through what makes them different at a molecular level, how they’re typically sold in the Canadian market, and what to compare when choosing between them for research purposes.

What’s the mechanistic difference between them?

Semaglutide is a single-receptor agonist. It binds selectively to the GLP-1 receptor and produces its effects through that pathway alone. The molecule is a modified version of the naturally occurring GLP-1 hormone with tweaks to extend its half-life and resist enzymatic breakdown.

Retatrutide is a triple agonist. It binds to three receptors simultaneously: GLP-1, GIP (glucose-dependent insulinotropic polypeptide), and glucagon. This multi-receptor engagement is what distinguishes it from semaglutide and from tirzepatide (which is a dual agonist covering GLP-1 and GIP but not glucagon).

The receptor coverage differences matter for research characterization. Studies looking at any of these compounds are examining different signalling pathway combinations, which is why the research literature treats them as related but distinct compounds rather than interchangeable.

How do the vial sizes and formats compare?

Both compounds ship as lyophilized powder in glass vials. Common Canadian market sizes:

Semaglutide: 2mg, 5mg, and 10mg vials are typical. Some vendors also offer larger 15mg or 30mg vials.

Retatrutide: 5mg, 10mg, and 20mg vials are more common. Some vendors carry 30mg vials.

The vial mechanics are identical — same 3ml or 5ml glass vial, same rubber stopper, same reconstitution process with bacteriostatic water. The only real handling difference is that larger vial sizes contain a larger lyophilized puck and take slightly longer to dissolve.

Reconstitution volume choice depends on target concentration, same as any peptide. A 10mg semaglutide vial with 2ml of water gives 5mg/ml. A 10mg retatrutide vial with the same 2ml of water gives the same 5mg/ml. The compound identity doesn’t affect the math.

Which is more available in the Canadian market?

Both are widely available from Canadian research-use peptide vendors, though retatrutide has been the growth story of the last two years. When it first hit the peptide research market, availability was thin and prices were high; both have normalized as more manufacturers started producing it.

Semaglutide has been available in the research market for longer and has broader vendor coverage. If you compare vendor catalogues, semaglutide is stocked by nearly every serious operator; retatrutide is stocked by most but not all.

Prescott Bio carries both. The catalogue at /peptides-canada shows the current available sizes and pricing for each.

How do the prices compare?

Retatrutide is generally more expensive per milligram than semaglutide, mostly because it’s a more complex molecule and synthesis scaling is still catching up to demand. The exact gap varies by vendor and by vial size — larger vials of both compounds have better per-mg pricing than smaller vials.

Rough general shape (specifics change over time): a 10mg semaglutide vial might sit around a certain CAD price point, and a 10mg retatrutide vial from the same vendor might be 50-100% higher. This isn’t a fixed ratio and it moves as manufacturing supply changes.

If you’re comparing across vendors, compare per-mg cost of the same vial size for the same compound rather than sticker price. A vendor selling a 20mg vial cheaper per mg than another vendor’s 10mg vial is offering better value if you can use the larger size.

What about storage and handling differences?

Storage requirements are essentially identical. Both compounds are stable long-term as lyophilized powder in the freezer (-20°C), stable for months refrigerated (2-8°C), and stable for weeks in solution when reconstituted with bacteriostatic water.

Both compounds should be reconstituted with the same slow-injection-down-vial-wall technique to avoid foaming. Both should be gently swirled, never shaken. Both should be stored on a stable fridge shelf, not in the door.

Neither is particularly light-sensitive relative to other peptides, but standard practice is to store in the original packaging or an opaque container regardless. Neither should be frozen once reconstituted.

Are the CoA specs the same?

The same two headline tests apply — HPLC for purity and mass spec for identity — but the specific values differ because they’re different molecules.

For semaglutide, look for HPLC purity of 98%+ and mass spec confirming the semaglutide molecular weight around 4113.6 daltons.

For retatrutide, look for HPLC purity of 98%+ and mass spec confirming the retatrutide molecular weight around 4731 daltons.

Otherwise the CoA checks are the same: batch number matches the vial, testing date is recent, third-party lab is named and verifiable, and both HPLC and mass spec sections are present rather than a single-test report.

What should Canadian buyers actually compare between the two?

Availability, price, and CoA quality from the specific vendor for the specific batch. The molecular differences matter for research characterization but don’t affect the sourcing evaluation — you’re evaluating vendor quality either way.

Ask for a batch-matched CoA before ordering, whether it’s semaglutide or retatrutide. Confirm the vendor ships domestically within Canada (rather than dropshipping from the US or Asia). Check the payment methods offered and whether you’re comfortable with them.

Storage and handling are identical, so infrastructure investment (fridge space, syringe stock, bacteriostatic water) doesn’t change based on which one you order.

Questions Canadian buyers ask about this

Are retatrutide and semaglutide interchangeable?

No. They’re related GLP-1-family compounds but they have different receptor coverage and different research literature. Treat them as distinct compounds.

Which one is easier to source in Canada?

Both are widely available from serious Canadian vendors. Semaglutide has broader vendor coverage; retatrutide is available from most vendors but not all.

Do they need different reconstitution water?

No. Bacteriostatic water works for both. The mechanical reconstitution process is identical.

Why is retatrutide more expensive?

Complex molecule, still-scaling manufacturing supply, and higher demand than production capacity in the research market. Pricing has been trending down as supply catches up.

Can I use the same syringes for both?

Yes. Insulin syringes work for both. The mg-per-unit calculation depends on the concentration you reconstitute to, not on which compound you’re drawing.

Published 2026-08-03. Refreshed as needed.