How to read a peptide certificate of analysis
This page has not yet been reviewed by a credentialed medical professional. It is educational and is not medical advice.
"Third-party tested" sounds reassuring. Here is what the numbers on a certificate mean, and the big safety questions they leave open.
What a certificate can show
- HPLC purity (%)
- The share of the main peak relative to other detected peaks in a chromatogram. It reflects peptide-related impurities only. A high number does not tell you how much peptide is actually in the vial.
- Mass spectrometry (identity)
- Confirms the molecular weight matches the expected compound. Without it, "99% pure" could be 99% of the wrong thing.
- Net peptide content
- The actual percentage of the powder that is peptide, as opposed to salts, water and counter-ions. It can be far below 100%, so a "5 mg" vial may contain less active peptide than labelled.
- Lot number and test date
- A certificate only describes one lot. If the number does not match your vial, it describes nothing about your vial.
What a certificate usually does not cover
- Sterility. Injectables must be sterile; most peptide certificates do not test for it.
- Endotoxin. Bacterial fragments can cause fever and inflammation even in a "pure" product.
- Heavy metals and residual solvents unless explicitly tested.
- Consistency across vials. Testing one vial does not guarantee the next.
Red flags
- No lot number, or a number that does not match your vial.
- A certificate you cannot verify with the lab that supposedly issued it.
- HPLC purity with no mass spec identity confirmation.
- Purity quoted without net peptide content.
- Health claims on the seller's page: a legitimate drug is sold with a label, prescribing information and a prescription.
The safer path
Medicines authorized by a regulator carry quality controls (sterility, endotoxin and manufacturing standards) that certificates from unregulated sellers cannot replace. For approved peptide drugs such as semaglutide and tirzepatide, use a licensed pharmacy.
FAQ
Does 99% HPLC purity mean a peptide is safe to inject?
No. HPLC purity is the share of the main peak among detected peptide-related peaks. It does not measure how much active peptide is in the vial, and it says nothing about sterility, endotoxin, heavy metals or whether the product is the compound claimed.
Can a certificate of analysis be fake?
Yes. A certificate shows what one sample tested, can be copied or edited, and may not match the vial you receive. A real report ties to a specific lot and, ideally, a lab you can contact independently.
Educational only, not medical advice.