How to Read a Certificate of Analysis
A COA can look official and still tell you very little. How to read a peptide certificate of analysis line by line, and how to check it's real.
In short
A certificate of analysis (COA) is a lab's report on one batch of a product. It describes one lot, on one date, for the tests listed on the page, and anything not on the page wasn't checked. Read it in four steps (which lot, which lab, which tests, which results), then confirm it with the lab yourself. Even a genuine, complete COA only tells you what's in the vial. It isn't FDA approval, and it says nothing about whether a peptide works or is safe.
- A COA is a receipt for one test of one batch, not a certificate of quality for a brand.
- Each test answers one question. Identity, purity, content, endotoxin and sterility are separate checks, and a "99% pure" result answers only one of them.
- Match the lot number to your vial, find the lab yourself, and confirm the report through the lab's own verification page, not a link from the seller.
- Even a perfect COA isn't FDA approval, can't see what happened after testing, and says nothing about the evidence for a peptide.
Many peptide sellers post a certificate of analysis, or COA, next to the product. It's usually a PDF or screenshot with a lab logo, a table of results and a big number like "99% pure". It looks like proof. Sometimes it is. Sometimes it's a test of a different batch, from a lab you can't find, covering only one thing.
In our last post we mapped the three lanes a peptide can travel: prescription, gray market and black market. This guide picks up the question that came after: if a seller shows you a COA, what are you actually looking at? We'll go through it line by line, explain what each test does and doesn't answer, and show you how to check that it's real.
What is a COA?
A certificate of analysis is a lab's report on one specific batch of a product. A batch is also called a lot. A COA lists what was tested, which method was used, what result was expected and what result the lab got.
Think of it as a receipt for a test, not a certificate of quality. It describes one lot, on one date, for the tests listed on the page. Anything not on the page wasn't checked.
Three questions to keep in mind:
- Which lot? A COA covers one batch, never a whole brand.
- Which lab? A named, independent lab you can contact.
- Which tests? Each test answers one question. Missing tests leave gaps.
How do you read one, line by line?
Below is a made-up, complete COA, with notes on what each line tells you.
This is not a real lab or product, and the limits are made up for the example. "EU" means endotoxin units.
| # | Line | Example |
|---|---|---|
| 01 | Lab | Northfield Analytical · ISO/IEC 17025 accredited |
| 02 | Product | Peptide X · 5 mg vial |
| 03 | Lot number | LOT 24-1187 |
| 04 | Dates | Received 14 Oct 2026 · Tested 16 Oct 2026 |
| 05 | Verification | Code 7Q4-K2M · check on lab website |
| Test | Method | Spec | Result |
|---|---|---|---|
| Identity | LC-MS | Matches expected mass | Conforms |
| Purity | HPLC | ≥ 98.0% | 99.1% |
| Peptide content | HPLC vs. reference | 4.50–5.50 mg | 4.92 mg |
| Endotoxin | LAL | ≤ 5.0 EU/mg | 0.8 EU/mg |
| Sterility | USP <71> | No growth | No growth |
What each line tells you:
- Who did the testing. Look for a named, independent lab with an address and contact details. ISO/IEC 17025 is the international standard for testing-lab competence 1; accreditation bodies publish directories you can search 7.
- What was tested. The product name and labeled amount should match the vial exactly.
- Which batch. The lot number links this report to one batch. It should match the number printed on your vial.
- When. Received and tested dates show the report is current and belongs to a recent batch.
- How to confirm it. Many labs offer a verification code or lookup page so you can check the report matches their records.
- The results table. Each row should name the test, the method, the target ("spec") and the result. A result without a spec gives you nothing to compare against.
What does each test answer?
Peptide COAs usually mix a few of the tests below. Knowing which question each one answers makes it easier to spot what's missing.
| Test | Common method | Answers | Doesn't answer |
|---|---|---|---|
| Identity | Mass spectrometry (MS, LC-MS) | Is this the right molecule? | How much of it there is, or how pure. |
| Purity | HPLC | What share of the peptide material is the target peptide? | Whether it's sterile or free of bacterial toxins. |
| Content | HPLC against a reference standard | How much peptide is actually in the vial? | Whether the peptide is the right one, unless identity was also tested. |
| Endotoxin | LAL test (USP <85>) | Are bacterial toxins below a set limit? | Whether live microbes are present. |
| Sterility | USP <71> | Did any microbes grow from the sample? | What the product is or how pure it is. |
Mass spectrometry identifies a molecule by its mass 6. HPLC separates a sample into its components, which is how it measures purity and, against a reference standard, amount 5. Endotoxin testing looks for toxins from bacteria, usually with a test made from horseshoe crab blood called LAL 3,4.
"99% pure" answers one question, not all of them. Purity is measured on the peptide material in the sample. A product can score high on purity and still carry bacterial toxins, live microbes or less peptide than the label says.
How can you check a COA is real?
A PDF is easy to copy, crop or edit. These five checks take a few minutes and catch most problems:
- Match the lot number. The lot on the COA should match the lot printed on the vial or box. No match, no meaning.
- Find the lab. Search the lab's name. It should have a real website, address and phone number. If it claims accreditation, look it up in the accreditor's public directory 7.
- Ask the lab directly. Use the lab's own verification page or contact details, not a link from the seller, to confirm the report and its results.
- Check the dates. A recent test date for a recent batch. Be wary of one COA reused for months or years.
- Look for what's missing. Compare the tests listed against the five above. A COA with only a purity number leaves most questions open.
What can't even a perfect COA tell you?
A genuine, complete COA from an accredited lab is a good sign about one batch. It still isn't the same as the checks a prescription medicine goes through, where manufacturers must follow federal manufacturing and quality-control rules 2.
- It isn't FDA approval. Approval looks at whether a drug works and is safe in people. A COA only looks at what's in the vial.
- It doesn't cover the trip. Heat, time and handling after testing can change a peptide. The COA can't see any of that.
- It says nothing about evidence. A pure sample of a poorly studied peptide is still poorly studied.
A COA on a product labeled "for research use only" doesn't make it suitable for people. As we covered last time, that label means the product wasn't made or reviewed for human use.
The takeaway
A COA is a receipt for one test of one batch. Read it in four steps: which lot, which lab, which tests, which results. Then confirm it with the lab yourself.
A real COA can tell you what's in the vial. It can't tell you whether you should use it. That's still question four: where did it come from, and what's the evidence?
References
- [1]ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratoriesInternational Organization for Standardization · ISO · 2017
- [2]21 CFR Part 211: Current Good Manufacturing Practice for Finished PharmaceuticalsElectronic Code of Federal Regulations (eCFR)
- [3]Guidance for Industry: Pyrogen and Endotoxins Testing: Questions and AnswersU.S. Food and Drug Administration · FDA
- [4]General Chapter <85> Bacterial Endotoxins Test: Notice of Adoption of Harmonized StandardUnited States Pharmacopeia · USP
- [5]High-performance liquid chromatographyWikipedia
- [6]Mass spectrometryWikipedia
- [7]Directory of accredited organizationsAmerican Association for Laboratory Accreditation (A2LA) · A2LA
Frequently asked questions
What is a certificate of analysis?
A lab's report on one specific batch, or lot, of a product. It lists what was tested, which method was used, what result was expected and what result the lab got. Anything not on the page wasn't checked.
If a COA says 99% pure, is the product safe?
Not necessarily. Purity is measured on the peptide material in the sample. A product can score high on purity and still carry bacterial toxins, live microbes, or less peptide than the label says. Those need their own tests.
How can I tell if a COA is real?
Match the lot number to the one on your vial, find the lab's own website and contact details, and confirm the report through the lab's verification page or by contacting the lab directly, not through a link from the seller. Check the dates, and look for missing tests.
Does a COA mean a peptide is FDA-approved?
No. FDA approval looks at whether a drug works and is safe in people. A COA only looks at what's in one batch, on the day it was tested.
The Pepwise Research Team reads the published research on peptides and summarises what it does and does not show.