How to read a peptide COA
A COA (certificate of analysis) is a lab report on one batch. It's useful, but only if you know what each number means and what it leaves out.
What a COA is
A lab tested a sample from a batch and wrote down what it found. That's it.
A good one answers three questions:
- Is it the right thing? (identity)
- How clean is it? (purity)
- How much is in the vial? (quantity)
Many COAs only answer the first two.
The numbers that matter
| On the report | What it tells you | What to look for |
|---|---|---|
| Identity (mass spec, MS) | The molecule's weight matches the peptide it's supposed to be | Measured mass close to the expected mass |
| Purity (HPLC) | Of the peptide material in the sample, what share is the right peptide | A percentage, with the test trace attached |
| Quantity / content | How many mg are really in the vial | A number in mg, near what the label says |
| Endotoxin | Leftover bacterial toxins | A result under the lab's stated limit |
| Sterility | Whether anything grew from the sample | "No growth" |
Endotoxin and sterility are separate tests and often cost extra, so plenty of COAs skip them. A missing test isn't a pass.
Purity is not quantity
This is the one people miss.
99% purity means the peptide that's there is clean. It doesn't say how much is there. A vial labeled 10 mg can test at 99% pure and still hold 7 mg.
If the COA shows purity but no mg figure, you know it's clean. You don't know the dose.
Check that it's real, and that it's yours
- Who ran it? An outside lab is worth more than the seller testing its own product.
- Does the batch or lot number match your vial? A COA for a different batch tells you nothing about yours.
- How old is it? A report from two years ago isn't about what's shipping now.
- Can you confirm it? Many labs put a code or link on the report so you can look it up on the lab's own site. Use it. Screenshots are easy to edit.
Red flags
- No batch or lot number
- No lab name, or a lab you can't find anywhere
- The same COA used for every batch
- A cropped or blurry image instead of the full report
- Purity listed with no test trace and no quantity
- A report that can't be looked up with the lab
What a COA can't tell you
A COA covers the sample that was tested. It can't promise every vial in the batch matches, and it says nothing about how your vial was stored or shipped afterward.
Treat it as one good piece of evidence, not a guarantee. For the rest of what to check, see where to source. Good storage on your end still matters.
Written by Amino Help as a general explainer. It isn't from the guide and it isn't medical advice.