Start with the details at the top
A certificate of analysis, usually shortened to COA, is a laboratory report for a particular sample. Before looking at the biggest percentage, check the sample name, batch identifier, laboratory, and report date. These tell you what was tested and when. A report for one batch does not describe every other batch with the same strain name.
Then look at the sections included. Cannabinoids, terpenes, pesticides, microorganisms, and toxic elements answer different questions. A cannabinoid table tells you about the compounds listed in that table; it does not tell you whether every other type of test was performed.
Make sense of the numbers
Pay attention to units. Percent by mass and milligrams per gram describe concentration by weight. Milligrams per milliliter describes concentration by volume. A result may also be reported on a dry-weight basis, which accounts for moisture. Compare like with like rather than assuming every number uses the same scale.
The small print matters too. ND generally means the test did not detect the substance under its stated conditions. LOQ means limit of quantitation: the lowest level the method can reliably put a number on. A result below that limit does not prove the substance is completely absent. The report's key should explain its abbreviations.
Read the report as a whole
Imagine one report shows a terpene result as a percentage and another uses milligrams per gram. The numbers may look very different even before you consider differences between the samples. Checking the units prevents a misleading comparison.
Laboratory measurements also have uncertainty. Reference materials, such as those developed by NIST, help laboratories check that their methods are working properly. Extra decimal places do not make a result exact. Keep the sample details, units, and test scope alongside any number you save; they give that number its meaning.
Sources & further reading
- California Department of Cannabis Control, testing and certificate-of-analysis regulations
- Oregon Liquor and Cannabis Commission, reporting limits and cannabinoid labeling terminology
- NIST (2024), Hemp reference material and measurement uncertainty
Last reviewed October 2026. Educational information, not individual medical or legal advice.