How to Read a Tirzepatide COA

Tirzepatide is a dual GIP/GLP-1 receptor agonist, and it's the heaviest molecule in the family by a clear margin — nearly 5 kDa. That size makes it both harder to synthesize cleanly and more expensive per vial, which is exactly the combination that attracts counterfeit paperwork. Fortunately, tirzepatide has a fixed, published molecular weight, which makes the single most important check on its COA completely objective.

The identity check: tirzepatide's verified numbers

These are the values a tirzepatide 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 "tirzepatide" that isn't around 4,813 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 tirzepatide.

Telling tirzepatide apart from its neighbours

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

The gaps are large. Tirzepatide and semaglutide are roughly 700 Da apart; tirzepatide and retatrutide about 82 Da — close enough that it's worth double-checking the formula, not just the rounded mass, since retatrutide is the one near-neighbour where a sloppy comparison could blur the two. There is no instrument error that turns one into another at these gaps. 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.

Charge states on a molecule this size

At nearly 4,813 Da, tirzepatide's mass spectrum is unlikely to show a clean singly-charged [M+H]⁺ peak as the dominant signal — molecules this large typically ionize into multiple charge states, commonly [M+2H]²⁺ and [M+3H]³⁺. Each should resolve back to the same underlying molecular weight once the charge is accounted for. A COA reporting only a single small m/z value with no explanation of charge state, on a compound this size, is a detail worth asking the vendor about.

Salt forms don't change the molecular weight

As with other research peptides, tirzepatide may ship as a TFA or acetate salt. 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 regardless of salt form.

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

Tirzepatide is a long, doubly-acylated peptide, and larger peptides are harder to synthesise cleanly than short ones. Expect a purity figure supported by an actual chromatogram, not a bare number:

• A purity percentage with decimal precision — 97.86%, not "98%". 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 large 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 and complexity are typically deletion sequences and truncated chains — normal synthesis by-products, and if anything more likely to appear than in a shorter peptide. 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/GIP COAs

• Brand names on the certificate. A legitimate analytical report describes a compound — "tirzepatide" — not a trademarked medicine. Mounjaro or Zepbound 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 tirzepatide with something else 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 tirzepatide and semaglutide 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.
• Mass reported without a charge state on a molecule this large, with no explanation of how a single-digit m/z value corresponds to a ~4,813 Da compound.
• 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 tirzepatide 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, and larger peptides are not more forgiving of poor handling.
• 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. Tirzepatide is an approved prescription medicine; research-grade material is neither equivalent to nor a substitute for a product dispensed by a licensed pharmacy.