How to Read a Cannabis COA: THC, CBD, Contaminants and Batch Numbers

A Certificate of Analysis, or COA, is a laboratory report describing a particular tested sample. It may contain cannabinoid results, batch identification and the findings of selected safety tests.

However, a document labelled COA does not automatically mean that every possible parameter has been tested. To understand what a report actually tells you, it needs to be read as a whole.

Start with the batch identification

One of the most important parts of a COA is the identification of the sample. A report may use a batch number, lot number, sample ID or another tracking code.

This information helps connect the laboratory report to the specific batch it is intended to describe.

If a report cannot be matched to a particular batch, its practical value is significantly reduced.

Testing date

Look for the date the sample was received and the date testing was performed, when those details are provided.

An old laboratory report does not necessarily describe a new batch of the same strain. Products with the same name can come from different harvests or production cycles.

THC and CBD

Cannabinoid results are usually one of the most visible parts of a COA.

Depending on the laboratory, the report may list THC, THCA, CBD, CBDA and other compounds separately or provide calculated totals.

Do not look only at the largest number on the page. Units and the way results are reported also matter.

Cannabinoid potency is not the whole COA

A THC result alone does not tell you whether the sample was tested for contaminants.

Potency analysis and safety testing should therefore be treated as separate parts of laboratory evaluation.

Microbiological testing

Broader laboratory programmes may include microbiological testing.

These tests can examine selected microorganisms or other microbiological parameters included in a particular testing method.

Always check the actual list of analyses rather than assuming a microbiological screen was performed simply because the document is called a COA.

Heavy metals

Some laboratory reports include testing for heavy metals. The specific elements tested depend on the laboratory programme and applicable requirements.

If this section matters for the product you are evaluating, confirm that the results are actually present in the report.

Pesticides and residual substances

A COA may also contain selected tests for pesticides, residual substances or other potential contaminants.

Testing panels differ. If a particular compound is not listed, that should not automatically be interpreted as proof that it is absent; it may simply not have been part of the analysis.

What do Pass and Fail mean?

Some reports display Pass or Fail next to a result.

Those labels normally relate to a threshold used by the laboratory or applicable standard. To interpret them properly, look at the measured result, units and corresponding limit when available.

Check the laboratory information

A useful report should make it possible to identify the laboratory that performed the analysis.

Look for the laboratory name, testing date, sample identifier, analytical methods and other information that helps establish where the document came from.

Potential warning signs

A report deserves closer examination if it cannot be linked to a batch, has no clear testing date, does not identify the laboratory or is presented only as a cropped image showing a small part of the results.

A professional-looking chart also does not guarantee comprehensive testing. A COA is informative only within the scope of the tests that were actually performed.

COA and GACP answer different questions

A COA describes laboratory findings for a sample. GACP relates to the cultivation, collection and initial handling of medicinal plant materials.

They therefore address different parts of quality assurance rather than being two names for the same certificate.

Read our guide to GACP vs COA → for a direct comparison.

The wider quality chain

Laboratory testing is easier to understand as one part of a longer chain:

origin → cultivation → harvest → batch identification → laboratory testing → documentation → traceability.

The more of that chain can be connected, the easier it becomes to understand the history of a particular product.

The takeaway

When reading a cannabis COA, look beyond THC and CBD. Check the batch number, testing date, laboratory, tests actually performed and whether the report can be connected to the product it is supposed to describe.

Continue with our Thailand Cannabis GACP guide →, our GACP vs COA comparison → and our overview of cannabis rules in Thailand →