How to Read a Retatrutide COA

New, heavily discussed compounds attract demand faster than reliable supply, and that gap is where weak paperwork thrives. A forged Certificate of Analysis costs a vendor nothing to produce, and most buyers can't tell a real one from a template edited in an image editor. The useful fact about retatrutide is that its molecular weight is fixed — so the single most important check on its COA is objective. The catch is that its closest neighbour is close.

The identity check: retatrutide's reference numbers

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

Two separate comparisons matter, and they catch different problems:

1. The theoretical mass printed on the COA vs. the value above. If the document states a theoretical weight for "retatrutide" that isn't around 4,731 Da, it 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 retatrutide.

Telling retatrutide apart from its neighbours

GLP-1 and related compounds are frequently confused, relabelled, or swapped. Most of them are hundreds of daltons from retatrutide, so mass spectrometry separates them easily. One is not:

Mazdutide is about 255 Da away and semaglutide about 618 Da — comfortably distinct. Tirzepatide is only about 82 Da away, the smallest gap in the family. That is still far outside instrument error, but it is small enough to disappear into a careless comparison: rounding to the nearest thousand, reading a mass off a chart axis, or comparing a monoisotopic observation to an average reference can all blur an 82 Da difference.

A worked example: the same sample in different charge states

Molecules this large rarely show a clean singly charged peak. They ionize into several charge states, and the spectrum shows m/z (mass divided by charge), not mass directly. For a protonated ion, m/z = (M + z × 1.007) ÷ z. Here is where each compound should appear:

A COA that lists a charge-state series and a deconvoluted mass makes this easy: the deconvoluted figure should land near 4,731, not 4,813. A COA that shows only a single unlabelled m/z value on a compound this size, with no stated charge, gives you nothing to anchor the comparison to — and is worth querying.

Salt forms don't change the molecular weight

Retatrutide 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 apply regardless of salt form.

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

The purity section

Retatrutide is a long, modified peptide, and compounds this size 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 — 97.64%, 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 size with no minor peaks at all is less believable than one showing trace impurities at 0.1–1%.

For why an exact 100% is a signal in its own right, see why 100% purity is a red flag.

Red flags specific to retatrutide COAs

• A theoretical or observed mass near 4,813. That is tirzepatide's mass. The single most important retatrutide-specific check.
• Approval or "clinical grade" language. A compound that is still investigational has no approved pharmaceutical form for a vendor to match. Claims of "pharmaceutical grade," "GMP," or "clinical-trial material" without an accreditation or certificate number to verify are unregulated marketing language on a research-market document.
• A single molecular weight for a blend. Products combining retatrutide with another compound are mixtures, and a mixture has no single molecular weight. A COA quoting one figure for a multi-component product is describing something that cannot exist.
• The same chromatogram across different GLP-1 products. If a vendor's retatrutide and tirzepatide certificates show identical peak shapes, retention times, or impurity profiles, at least one is fabricated — these are different molecules.
• Mass reported without a charge state on a molecule this large, with no explanation of how a small m/z value corresponds to a ~4,731 Da compound.
• An old or missing analysis date on a fast-moving product line.
• No mass spectrometry at all. HPLC alone establishes purity, not identity. For a compound with a close neighbour, 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 retatrutide COA cannot tell you

• 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 a pharmaceutical product. A clean COA on research-grade material does not make it one.

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. Retatrutide is an investigational compound; research-grade material is not a pharmaceutical product.