Guide
How to read a certificate of analysis
A certificate of analysis (COA) is a lab report on a specific batch of product. It's the best tool you have for judging a vendor, if you know what to look for.
What a good COA includes
| Item | What to check |
|---|---|
| Lot or batch number | It must match the number on your vial. A generic COA for "the product" proves nothing about your batch. |
| Testing lab | An independent lab, named, ideally ISO 17025 accredited. "Tested in-house" isn't third-party testing. |
| Purity (HPLC) | Reported as a percentage, usually 98% or higher. Look for the chromatogram, which is the graph behind the number. |
| Identity (mass spectrometry) | Confirms the molecule is what the label says by matching its expected molecular weight. |
| Quantity | Confirms the vial contains the stated amount, for example 5 mg. |
| Date | Should be recent and close to the batch's production date. |
| Endotoxin and sterility | Optional extras that better vendors include. |
Red flags
- No lab name, or a lab you can't find online
- The same COA reused for different batches or products
- Purity exactly 99.9% on every product
- Edited-looking documents, or COAs supplied only as low-resolution images
- The lab can't confirm the report when you contact them
In 2026 a vendor's owner was sentenced to federal prison after admitting to forging lab certificates. Many testing labs will confirm whether a report is genuine. If a vendor's COA looks wrong, ask the lab.
Last reviewed: November 2026