Cagrilintide testing: what a lab test shows, semaglutide mix-ups and how published samples fail

What a cagrilintide test shows

A cagrilintide test answers the same three questions as any peptide test. Is it cagrilintide? How pure is it? How many mg are in the vial? LC-MS answers the first with a mass match, HPLC the second, and a quantitative assay the third. The cagrilintide compound page gives a recommended panel by product form:

Product form	Recommended tests
Freeze-dried vial, liquid vial or pen cartridge	Identity (LC-MS), purity (HPLC), content per vial, endotoxin (LAL), Sterility (USP <71>, 14 days)
Raw powder	Identity (LC-MS), purity (HPLC), content per vial, counter-ion (TFA, acetate), water content (Karl Fischer)

The identity test compares the measured mass with cagrilintide’s calculated monoisotopic mass, 4406.2515 Da. An LC-MS run looks for its multiply charged ions, calculated at m/z 1469.7578 (3+), 1102.5702 (4+) and 882.2576 (5+). The formula is C194H312N54O59S2 and the CAS number 1415456-99-3.

Cagrilintide test results in published data

Finnrick, a US platform that publishes results from community-submitted samples, gives pass and fail counts by product. In its public data summary read on 4 October 2026, cagrilintide had 194 published tests from 43 vendors, the first on 20 April 2025 and the latest on 14 September 2026. 105 passed, 88 failed and 1 was incomplete. About 46% of classifiable samples failed.

That is about twice the fail share of retatrutide or tirzepatide (near 21–22% in Finnrick’s September data, on thousands of tests each). The cagrilintide set is much smaller, so one vendor’s batches can move the figure. Finnrick’s default standard, Purity Focus, fails a sample for a wrong identity, purity under 99.5%, or a fill more than 35% above or below the label claim. Overfill fails too. The guide to peptide fail rates shows where cagrilintide sits among other products.

Demand is high even though public test counts are low. In a September 2026 interview, Finnrick’s chief executive said retatrutide and cagrilintide together make up 38% of its test requests.

Cagrilintide is an amylin analogue, not a GLP-1

Cagrilintide belongs to a different class from semaglutide, tirzepatide and retatrutide: it is an amylin analogue. Buyers often group it with GLP-1 peptides because it is sold beside them and blended with semaglutide.

This matters when you order a test. A blind GLP-1 identification checks a vial against a list of GLP-1 family candidates, and the report lists every candidate it looked for. If you think a vial might hold cagrilintide, order a standard identity test for cagrilintide, or ask the lab whether cagrilintide is on its candidate list before you send the vial.

Mix-ups with semaglutide

Cagrilintide and semaglutide differ by 295 Da (4406.25 against 4111.12 Da). An LC-MS run separates them easily. Retention time alone is weaker evidence, because long, modified peptides can elute in similar regions.

The two are easy to tell apart by mass: cagrilintide is about 295 Da heavier than semaglutide. A report that prints the observed mass shows at once which one is in the vial.

On a report, the sign is easy to read. A vial labelled semaglutide that holds cagrilintide shows an observed mass near 4406 Da, where the expected mass is 4111 Da. The semaglutide compound page lists semaglutide’s own calculated ions for comparison, and the semaglutide testing guide covers that side.

Cagrilintide and semaglutide blends

Cagrilintide is often sold blended with semaglutide. A blend needs a different kind of report:

• Identity for each peptide. Both masses should appear, each matched to its expected value.
• mg for each peptide. Each component needs its own reference standard and its own content result.
• No single purity figure. A blend is a mix by design, so one “purity” number for the whole vial means little.

Some labs list a cagrilintide and semaglutide blend as its own test; Janoshik’s peptide list is one example. The guide to peptide blend testing explains what a blend report should show.

How to read a cagrilintide result

1. Identity: expected mass 4406.2515 Da, the observed mass, and the error in ppm. Several charge states should agree.
2. Purity: % area at a stated wavelength, with the chromatogram and the impurity peaks.
3. Content: mg per vial as free base, the reference standard, the uncertainty, and the % of the label claim you supplied.
4. Safety tests, if ordered: endotoxin as a number in EU/mg and EU/vial; sterility named as the 14-day USP <71> test.

A test shows what was in the vial the lab received. It does not say whether a product is safe to use.

How to get cagrilintide tested

Ask for a quote and list the product form and the tests. The quote states how many vials to send; endotoxin and sterility each need their own unopened vials. Ship the vials sealed and numbered, and keep a photo of the lot number. For a group buy, send vials from different kits so the result shows how much they vary.

What HK Analytical does for cagrilintide

We test cagrilintide as one sample with any mix of identity (LC-MS), purity (HPLC), content per vial, endotoxin (LAL), Sterility (USP <71>, 14 days), residual solvents, counter-ion (TFA, acetate), water content (Karl Fischer) and vial-to-vial consistency. We do not offer per-component blend analysis. Results within days of receipt. Sterility (USP <71>, 14 days) is the one test that takes 14 days, because the method incubates for 14 days. Every number comes with its raw data, the report is a signed record you can check at hkanalytical.com/verify, and it shows our photo of the vial as received. See the example report or request a quote.