How to Read a Certificate of Analysis

What a CoA actually tells you

A Certificate of Analysis is a lab report that confirms what's in a product and what isn't. Think of it as a snapshot: purity percentage, identity confirmation, contamination screening, and sometimes potency. It's issued by an independent laboratory after testing a specific batch.

Not all CoAs are created equal. Some test only for the compound you ordered. Others screen for heavy metals, endotoxins, or microbial contamination. The scope depends on what the manufacturer paid to test and what the lab is accredited to measure.

The top section: batch and identity

Every legitimate CoA starts with identifying information. You should see a batch or lot number, test date, and the name of the compound tested. This section also lists the testing laboratory and sometimes an accreditation number.

The batch number matters. It should match the label on your product. If a vendor shows you a CoA from six months ago or a different batch entirely, you're looking at someone else's results, not yours.

Identity testing usually involves HPLC or mass spectrometry. The lab compares the sample against a reference standard to confirm you're getting the peptide you ordered, not a different molecule or a mix.

Purity percentage: the number everyone fixates on

Purity refers to how much of the sample is the target peptide versus everything else—salts, residual solvents, manufacturing byproducts, water. A purity of 98% means 98% peptide, 2% other.

Most research-grade peptides fall between 95% and 99% purity. Anything below 90% is suspect. Anything claiming 100% is rounding or marketing.

Context matters. Some peptides are hygroscopic and absorb water from air, which lowers reported purity. Acetate salts add weight but are pharmacologically inert. A 96% purity with clear identity confirmation is often more trustworthy than a 99.5% result with no contamination screening.

Contaminant testing: what you don't want

A comprehensive CoA tests for unwanted substances. Common screens include:

Heavy metals. Lead, arsenic, mercury, cadmium. These accumulate with repeat exposure and have no place in anything you're putting in your body.

Endotoxins. Bacterial residues that trigger immune responses even in tiny amounts. Measured in endotoxin units per milligram. For injectables, you want this as close to zero as possible.

Microbial contamination. Tests for bacteria, yeast, mold. Sterile products should show zero colony-forming units.

If a CoA skips contamination testing entirely, assume the vendor either didn't pay for it or didn't like the results.

Red flags and missing pieces

A few warning signs that a CoA might not be worth the paper it's printed on:

No lab contact information or accreditation. Legitimate labs list their credentials and can be independently verified.

Blurry scans or obviously edited PDFs. If you can't read the fine print or the formatting looks inconsistent, question it.

Mismatched batch numbers. If the CoA is from a different lot than what you're buying, you have no idea what's actually in your vial.

Testing by the manufacturer's in-house lab. Third-party means independent. If the seller tests their own product, the conflict of interest is obvious.

Cherry-picked tests. A CoA that only shows purity but skips contamination screening is hiding something or cutting corners.

What a CoA can't do

Even a pristine CoA is a single data point. It tells you about one sample from one batch on one day. It doesn't guarantee sterility of your specific vial, especially if reconstitution or storage was mishandled after manufacturing. It doesn't confirm the peptide will work as expected in your body. And it can't replace the judgment of a prescribing practitioner who understands your health context.

CoAs are transparency tools, not safety guarantees. They let you filter out the worst actors and make more informed decisions about sourcing. But they're the beginning of due diligence, not the end.