How to Read a Retatrutide COA (Certificate of Analysis)

Almost every retatrutide seller in the UK now claims “≥99% purity” and shows a Certificate of Analysis. But a COA is only useful if you know how to read it, and if it is genuine. This guide walks through each section of a retatrutide COA, what the numbers mean, and the warning signs that a certificate is not worth the paper it is printed on.

Quick summary: A useful retatrutide COA comes from an independent lab, matches the batch number on your vial, shows HPLC purity with a chromatogram, confirms identity by mass spectrometry (molecular weight around 4,731 Da), and ideally measures the actual quantity in the vial. Generic, undated or unverifiable certificates prove very little.

Why the COA Matters So Much for Retatrutide

Retatrutide is an investigational compound with no licensed version, so there is no regulator checking research-grade material. It is also a large, complex 39-amino-acid peptide, which makes it harder to manufacture well than short peptides. The COA is the main evidence you have that the vial contains what it says, at the stated purity and quantity. For the wider context, see Why Third-Party COA Testing Matters.

The Sections of a Retatrutide COA

Section	What it tells you	What good looks like
Sample / product name	What was tested	“Retatrutide” with the stated vial content (e.g. 10mg)
Batch or lot number	Which production batch was tested	Matches the batch on your vial or label
Test date	When the analysis was run	Recent and consistent with the batch
Laboratory	Who ran the test	An independent lab you can identify and contact
HPLC purity	Percentage of the sample that is the target peptide	≥98%, ideally ≥99%, with a chromatogram
Mass spectrometry	Confirms identity by molecular weight	Observed mass consistent with ~4,731 Da
Quantity / content	How many mg are actually in the vial	Close to the labelled amount
Verification	Whether the COA can be checked	An online key, QR code or lab reference

Step 1: Check the Batch Number

A COA applies to one batch. If the batch number on the certificate does not match the batch on your vial, the certificate tells you nothing about your product. Be wary of sellers who show one certificate for every order, month after month.

Step 2: Read the HPLC Purity and Chromatogram

High-Performance Liquid Chromatography (HPLC) separates the components of a sample. The result is a chromatogram: a graph with peaks, where each peak represents a different compound.

Main peak: this should be retatrutide, and it should be tall and sharp.
Small peaks: these are impurities, such as truncated sequences, oxidised forms or synthesis by-products.
Purity %: the main peak’s area as a share of the total. 99% means about 1% of the detected material is something else.

A purity figure with no chromatogram is much weaker evidence. A perfect “100%” is a red flag: real analytical results almost always show some impurity.

Step 3: Confirm Identity With Mass Spectrometry

HPLC tells you how pure a sample is, but not what it is. Mass spectrometry (MS) measures molecular weight to confirm identity. Retatrutide has a molecular weight of roughly 4,731 Da. Because large peptides carry multiple charges in MS, reports often show several charge-state peaks or a deconvoluted mass. Either way, the result should be consistent with retatrutide.

If a COA shows purity but no identity test, you know the sample was pure, but not that it was retatrutide.

Step 4: Check the Quantity

Purity and quantity are different things. A vial can be 99% pure and still contain 7mg instead of 10mg. Under-filling is one of the most common problems in the research peptide market, and it quietly raises the real price per mg. The best COAs report a measured content in mg per vial. See for how to compare on price per mg.

Step 5: Verify the Certificate

Many independent testing labs offer a way to verify a report online, using a unique key, QR code or reference number. If a COA can be verified on the lab’s own website, it is far harder to fake. If there is no way to check it, treat it with caution.

Red Flags on a Retatrutide COA

No batch number, or a batch number that does not match your vial
No lab name, or a lab you cannot find or contact
Purity of exactly 100%
Purity stated with no chromatogram
No mass spectrometry or other identity test
Very old test date, or the same certificate used across many batches
Signs of editing: mismatched fonts, blurry numbers, pasted-in logos
The seller’s own name as the “laboratory” with no independent testing

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Frequently Asked Questions

What should a retatrutide COA include?

A batch number matching your vial, the testing lab, a test date, HPLC purity with a chromatogram, mass spectrometry confirming identity, and ideally a measured quantity per vial and a way to verify the report.

What purity should retatrutide be?

Good research-grade retatrutide is typically ≥98% pure by HPLC, and the best is ≥99%. A claim of exactly 100% is a warning sign.

What is the molecular weight of retatrutide?

Retatrutide has a molecular weight of approximately 4,731 Da. Mass spectrometry results should be consistent with this.

What is the difference between purity and quantity?

Purity is the percentage of the material that is retatrutide. Quantity is how many milligrams are in the vial. A vial can be highly pure but under-filled.

How can I tell if a COA is fake?

Check that the batch matches your vial, that the lab is real and independent, and that the report can be verified online. Look for signs of editing and be wary of 100% purity claims or reused certificates.

How to Read a Retatrutide Certificate of Analysis (COA)