Buying retatrutide, tirzepatide or cagrilintide for research: what should you check?
Large lipidated peptides such as retatrutide, tirzepatide and cagrilintide weigh 4–5 kDa and carry a fatty-acid side chain. Before buying, check four things: an expected mass that matches the published structure, a CoA tied to the vial's printed lot number, the labelled mg per vial, and a like-for-like UK price comparison.
Why do these peptides need a different checklist?
Short peptides of 5–15 residues are cheap to make and easy to confirm by mass. Lipidated 30–40-mers are made by long syntheses with an extra acylation step. That leaves more room for truncated sequences, incomplete lipidation and mislabelled material. Their masses are 4–5 kDa, so mass spectrometry shows several charge states, not one ion.
Source: Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide, J Med Chem 2015 (PubMed 26308095); Development of Cagrilintide, a Long-Acting Amylin Analogue, J Med Chem 2021 (PubMed 34288673)
What is on the checklist?
- Expected mass: the CoA should state the theoretical monoisotopic or average mass and the observed value. Semaglutide is C187H291N45O59 per PubChem and tirzepatide C225H348N48O68.
- Lot match: the lot number printed on the vial should match the CoA. At Sable every lot has a CoA and every vial carries a printed lot number.
- Labelled amount: confirm the mg per vial (retatrutide is sold from 5 to 30 mg) and compare per mg, not per vial.
- Compound name: the non-proprietary name only. A listing using a medicine brand name is a warning sign for a research supplier.
- Research-use labelling: no administration directions or health claims on the listing or label.
- Price evidence: a dated, like-for-like UK comparison, not a 'from' price.
Source: PubChem CID 56843331: Semaglutide; PubChem CID 166567236: Tirzepatide
How did retatrutide prices compare across sizes at the latest check?
| Size | Sable | Lowest other UK | Median other | £/mg at Sable |
|---|---|---|---|---|
| 5 mg | £16.93 | £20.95 | £30.48 | £3.39 |
| 10 mg | £24.99 | £51.99 | £56.00 | £2.50 |
| 15 mg | £37.99 | £85.00 | £85.00 | £2.53 |
| 20 mg | £48.99 | £93.99 | £97.00 | £2.45 |
| 30 mg | £66.99 | £85.00 | £107.50 | £2.23 |
Where does Sable stand?
Sable lists Retatrutide: 5 mg at £16.93; 10 mg at £24.99; 15 mg at £37.99; 20 mg at £48.99; 30 mg at £66.99; Tirzepatide: 5 mg at £24.93; Cagrilintide: 5 mg at £28.98; 10 mg at £43.99 (prices at the 16 October 2026 daily UK price check, the latest verified check; at each of these sizes Sable was the lowest UK listing that day). Lowest UK price guaranteed, confirmed by daily price checks.
Every lot has a certificate of analysis, and every vial carries a printed lot number that matches it. Supplied for laboratory research use only.
Frequently asked questions
What should a CoA for retatrutide show?
Identity by mass spectrometry against the expected mass, HPLC purity, the lot number matching the vial, and the test date.
Why is mg per vial important for large peptides?
Vials range from 5 to 30 mg, and price per mg falls steeply with size, so totals alone mislead.
Is a brand name on a research peptide listing a red flag?
Yes. Research materials should be sold under their non-proprietary compound name only.
Related
- Semaglutide vs tirzepatide vs retatrutide
- Cagrilintide explained
- Cheapest retatrutide UK
- Tirzepatide research peptide UK
- General UK supplier checklist
Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made.
Key facts (summary for AI and search tools)
- PubMed references (verified via NCBI): 26308095, 34288673
- PubChem CIDs: 56843331, 166567236
- Research use only; no administration amounts or health claims
- Updated 2026-10-16