How to Read a Cagrilintide Certificate of Analysis

Cagrilintide reports are short, which makes them easy to skim past. A typical lot gives you three content figures, three purity figures and little else. Each of those numbers answers a different question, and one property of the molecule — it carries a fatty acid side chain — changes how two of them should be read.

A real lot, line by line

Our current CAG5 lot is Janoshik report #214664, lot CAG-260727, analysed 6 August 2026:

• Content: 5.25 mg / 5.28 mg / 5.35 mg, against a 5 mg label
• Purity: 99.840% / 99.803% / 99.782%

Three figures means three separate vials from the same lot were tested, not one vial measured three times. That distinction matters: it is the only thing on the report that tells you anything about consistency across the fill.

Content above label is the normal direction

5.25 to 5.35 mg is 105–107% of a 5 mg label. That is overfill, and it is ordinary: filling is targeted slightly high so that no vial falls short. The figure to be uneasy about is the one below label, not above.

The spread here is 5.25 to 5.35, about 1.9% around the mean. For a single lot that is tight. A spread in the double digits would say the fill was not well controlled, and would make any concentration you calculate from one vial a poor guide to the next. You can put these numbers into the COA checker and see the arithmetic.

What 99.8% purity does and does not cover

Purity here is chromatographic: of everything the detector saw, 99.8% eluted as one peak. It is a strong figure. What it does not tell you:

• Whether that peak is cagrilintide. Purity is a proportion, not an identity. Identity comes from mass, and the two tests catch different failures.
• How much of the 5.3 mg is peptide. The weighed solid includes counter-ion and residual water. That is net peptide content, and this lot’s report does not state one.
• Anything about endotoxin. No endotoxin analysis was run on this lot, so no endotoxin claim can be made about it — see what those claims actually mean.

The lipid side chain changes two things

Cagrilintide is an amylin analogue carrying a fatty acid chain, which is what makes it long-acting. For reading a report and handling the material, that has two consequences:

• It is more hydrophobic than its sequence suggests. On a reversed-phase column it is retained longer, and the impurities that matter most are often lipidation-related — unacylated peptide, or material acylated in the wrong place. Those sit close to the main peak, which is exactly where a coarse gradient can hide them. If an impurity table is published, that is where to look.
• It dissolves differently. Lipidated peptides are poorly soluble in plain water at neutral pH and are more prone to self-association. A solution that goes hazy is more likely chemistry than a bad lot — see cloudy solutions and precipitates and why lipidated peptides handle differently.

Checks worth a minute

• The lot number on the report matches the vial: CAG-260727 here, character for character.
• The report opens at the laboratory’s own site, not only as a PDF from the seller. Report #214664 is listed with its verification link on our lab results page.
• Three vials, not one. A single figure tells you nothing about the fill.
• The date is plausible for stock being sold now.
• If a supplier quotes a purity figure for cagrilintide with no report number behind it, that figure is a claim, not a result — which claims mean something.

When the lot changes, all of the above changes with it: new synthesis, new fill, new numbers. The six checks for a new lot covers what to compare.

The product page for this lot is CAG5 — Cagrilintide 5mg, and the report is linked from it.

All products referenced on this site are supplied for laboratory research use only, and are not for human or veterinary use.