Guide · Last reviewed 16 October 2026

How to read a supplement lab report (COA)

A certificate of analysis (COA) or test report is a document showing what a lab measured in a sample. Here's how to tell whether it actually tells you something about the product in your hands.

1. Who did the testing?

Look for the laboratory's name and address, not just the brand's logo. An independent lab is stronger evidence than an in-house "manufacturer's COA". Check for accreditation to ISO/IEC 17025, the international standard for testing labs. In the UK this is granted by UKAS; in the EU by national bodies such as DAkkS (Germany), COFRAC (France) or ENAC (Spain). Many reports mark which individual methods are accredited.

2. Which product and which batch?

The report should name the product and give a batch or lot number, ideally with a sampling or test date. Results apply only to that batch. Compare the lot number with your pack. A report for a batch whose best-before date has passed is outdated.

3. What was measured?

Heavy metals: usually lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As), often by ICP-MS (e.g. method EN 15763).
Microbiology: total plate count, yeasts and moulds, E. coli, Salmonella.
Identity or active content: e.g. withanolides for ashwagandha, or the labelled vitamin or mineral amount.
Sometimes pesticides, mycotoxins or PAHs, depending on the ingredient.

4. Read the units and the result

Heavy metals are usually given in mg/kg, which is the same as ppm (parts per million); µg/kg is ppb. Some reports give µg per daily dose instead. "<0.01" means below the lab's limit of quantification, not necessarily zero. Prefer reports that show a measured value. A line that just says "<3 ppm, PASS" only tells you the result was under a limit, not what it was.

5. Compare with the legal limits

For food supplements, EU law sets maximum levels of 3.0 mg/kg lead, 1.0 mg/kg cadmium (higher for some seaweed products) and 0.10 mg/kg mercury (Regulation (EU) 2023/915). Great Britain uses the retained Regulation 1881/2006 with equivalent supplement limits. These are legal maximums, not targets.

Red flags

No lab name, or the lab is the brand itself.
No batch number or date, or a single old report used for years.
Specification-only results ("conforms", "pass") with no numbers.
A raw-ingredient COA from the supplier presented as a finished-product test.
An organic or GMP certificate presented as a lab report. These are useful but don't measure contaminants.
Cropped images instead of the full signed PDF.

We apply these checks when deciding a product's status: see our methodology.

Sources

Information only, not medical advice.