How to Read a Semaglutide COA

High demand plus high price is exactly the combination that attracts document fraud. A forged Certificate of Analysis costs a vendor nothing to produce, and most buyers can't tell a real one from a template someone edited in an image editor. The good news is that semaglutide has a fixed, published molecular weight — which makes the single most important check on its COA completely objective.

The identity check: semaglutide's verified numbers

These are the values a semaglutide COA should be consistent with:

Two separate comparisons matter here, and they catch different problems:

1. The theoretical mass printed on the COA vs. the real value above. If the document states a theoretical weight for "semaglutide" that isn't around 4,113 Da, the document is internally wrong — a strong sign it was edited from another compound's template.
2. The observed mass in the MS section vs. that theoretical value. This is what tells you the material tested was actually semaglutide.

Telling semaglutide apart from its neighbours

This is the check that catches substitution. GLP-1 and related compounds are frequently confused, relabelled, or swapped — but their masses are hundreds of daltons apart, so mass spectrometry separates them trivially. If a COA claims semaglutide and the observed mass lands on one of the other rows, you know exactly what you're looking at:

The gaps are large. Semaglutide and tirzepatide are roughly 700 Da apart; semaglutide and liraglutide about 362 Da. There is no instrument error that turns one into another. A mass sitting on the wrong row means the vial holds a different compound than the label claims — or the COA was copied from a different product entirely.

"Semaglutide sodium" and salt forms

Plenty of listings use the phrase "semaglutide sodium." This describes the salt form of the material, not a different peptide. The counterion adds weight to the powder in the vial, but it does not change the peptide's molecular weight — mass spectrometry still measures the peptide, so the figures above still apply.

What salt form does affect is how much actual peptide the vial contains by weight, which is a separate number entirely. See purity vs net peptide content.

The purity section

Semaglutide is a long, acylated peptide, and long peptides are harder to synthesise cleanly. Expect a purity figure supported by an actual chromatogram, not a bare number:

• A purity percentage with decimal precision — 98.42%, not "99%". Round numbers across a vendor's whole catalog are a fabrication tell.
• A stated specification — for example "Spec: ≥98%". A result without a spec is only half a result.
• The HPLC chromatogram, with a sharp main peak, stable baseline, and visible integration lines.
• Method parameters — column, mobile phase, flow rate, detection wavelength (214 nm or 220 nm).
• Small impurity peaks. A chromatogram of a peptide this size with absolutely zero minor peaks is less believable than one showing trace impurities at 0.1–1%.

Related-substance impurities in a peptide of this length are typically deletion sequences and truncated chains — normal synthesis by-products. Their complete absence is not a sign of quality; it's a sign the chromatogram may not be real.

Red flags specific to GLP-1 COAs

• Brand names on the certificate. A legitimate analytical report describes a compound — "semaglutide" — not a trademarked medicine. Ozempic or Wegovy branding on a COA suggests a document assembled for marketing rather than issued by a testing lab.
• "Pharmaceutical grade" or "GMP" claims without any accreditation or certificate number to verify. These phrases are unregulated marketing language on a research-market document.
• A single molecular weight for a blend. Products combining semaglutide with something else (B12/cyanocobalamin is common) are mixtures, and a mixture has no single molecular weight. A COA quoting one figure for a multi-component product is describing something that can't exist.
• The same chromatogram across different GLP-1 products. If a vendor's semaglutide and tirzepatide certificates show identical peak shapes, retention times, or impurity profiles, at least one is fabricated — these are different molecules and cannot produce the same trace.
• An old or missing analysis date on a product line that turns over quickly.
• No mass spectrometry at all. HPLC alone establishes purity, not identity. For a compound this heavily counterfeited, a COA without MS data leaves the most important question unanswered.

These sit on top of the universal checks — lab identity, accreditation, batch traceability, dates. For the complete list see the field-by-field COA checklist and the forgery red flags guide.

What a semaglutide COA cannot tell you

Even a COA that passes every check above has hard limits, and they matter more for this compound than most:

• It isn't a sterility or endotoxin test unless those tests are explicitly listed. Purity and identity say nothing about microbial contamination.
• It describes the tested sample, not necessarily the vial you received — that link exists only through a matching batch number.
• It says nothing about handling since testing. Peptides degrade with heat, moisture, and time.
• It is not a quality equivalence to an approved medicine. A clean COA on research-grade material does not make it a pharmaceutical product.

Frequently asked questions

Research use only. This article is for scientific and educational purposes and is not medical, dosing, or investment advice. Research peptides are not approved for human or veterinary use. Semaglutide is an approved prescription medicine; research-grade material is neither equivalent to nor a substitute for a product dispensed by a licensed pharmacy.