Key takeaways
- A COA is only useful if it matches the batch in your hand.
- Look for an independent, accredited lab, not just the brand's own paperwork.
- Check potency against the label, plus contaminants such as heavy metals and microbes.
- 'ND' means not detected, which is only meaningful alongside the test's detection limit.
A certificate of analysis (COA) is a lab report for a specific batch of a product. Reading one takes a few minutes and tells you far more than marketing copy does. Here is how to go through one, section by section.
1. Match the batch
Find the product name and lot or batch number at the top, then check it against the number printed on your container. A generic COA with no lot number, or one that does not match, proves very little.
2. Who ran the test?
Look for the lab's name and contact details. Independent labs accredited to ISO/IEC 17025 are a good sign. A report produced only by the manufacturer is less reassuring than one from a third party.
3. The tests that matter
| Test | What it checks |
|---|---|
| Identity and potency | That the active ingredients are present at the amount on the label, within a stated range. |
| Heavy metals | Lead, arsenic, cadmium and mercury, reported in units such as ppm or mcg per serving. |
| Microbial | Total plate count, yeast and mold, and pathogens such as E. coli and Salmonella. |
| Other contaminants | Pesticides or residual solvents, depending on the product. |
4. Read results against limits
Good reports show the specification (the limit or target) next to the result, with a clear pass or fail. If only results appear and no limits, you cannot tell whether they are acceptable. 'ND' means 'not detected', which depends on the test's detection limit, so it helps when that limit is listed.
5. Check the date and the method
Testing dates should be recent and close to the batch's manufacture date. Methods are usually named (for example HPLC for potency or ICP-MS for metals). You do not need to understand them in depth, but a report that names none is vague.
Red flags
- No lot number, or one that does not match your product.
- No lab name, or only an in-house report.
- Results with no limits or units.
- A COA that is years old or has been edited into a screenshot.
A COA is evidence, not a guarantee. It tells you about one batch on one day, which is why consistent testing across batches counts for more than a single impressive document.
Sources and further reading
- U.S. Food and Drug Administration: Dietary Supplements
- NIH Office of Dietary Supplements
- Health Canada
General reference sources, linked for further reading. Always check current guidance for your country and situation.
Reviewed and updated October 17, 2026. This article is for general information and is not medical advice. See our medical disclaimer.
