A certificate of analysis often runs to several pages, and most of it is unfamiliar. Knowing which types of cannabis testing exist, what each one measures and why it is on the panel makes the report far easier to use — whether you are releasing a batch or deciding what to buy.
Testing splits into two families. Composition analyses tell you what is in the product. Contaminant analyses tell you what should not be. Below is what sits in each, and what a result actually means.
Composition Testing
Potency and cannabinoid profile
Potency testing quantifies the cannabinoids present in a sample: THC and THCA, CBD and CBDA, and depending on the panel, minor cannabinoids such as CBG, CBN and CBC.
The distinction between the acidic and neutral forms matters more than most labels suggest. Raw cannabis contains mostly THCA, which is not intoxicating. Heat converts it to THC. Total THC is therefore a calculated figure that accounts for that conversion, which is why it does not simply equal the THC line on the report.
Results are expressed as a percentage by weight for flower and concentrates, and as milligrams per serving and per package for edibles, beverages and tinctures. Those are different units answering different questions, and they are not interchangeable.
Applies to: every cannabis product.
Terpene analysis
Terpene analysis identifies and quantifies the volatile aromatic compounds that give a cultivar its smell and flavour — myrcene, limonene, pinene, caryophyllene and dozens of others.
Terpene testing is frequently optional under compliance rules, which is why plenty of COAs do not include it. Commercially, that is changing. A terpene profile distinguishes two batches with identical potency figures, and it gives cultivators a concrete chemical reference to track between harvests. We cover the detail in terpenes and the entourage effect.
Applies to: flower, concentrates, vape products; optional in most jurisdictions.
Moisture content and water activity
These two measurements sound similar and are not. Moisture content is how much water is in the material by weight. Water activity is how much of that water is chemically available — and availability, not quantity, is what determines whether microorganisms can grow.
Water activity is the more useful of the two for predicting shelf stability. It is also the analysis that most directly reflects how well a batch was dried and cured.
Applies to: flower and other plant material.
Contaminant Testing
Microbial screening
Microbial screening looks for bacteria, yeast and mould, including specific pathogens such as E. coli, Salmonella and Aspergillus species. Some panels report total counts; others target named organisms. Most do both.
Microbial failures usually trace back to drying, curing or facility hygiene rather than to cultivation itself. Cross-reference an elevated result against water activity on the same report — the two are almost always related.
Applies to: flower, and many infused products.
Mycotoxin screening
Mycotoxins are toxic compounds produced by certain moulds, principally aflatoxins and ochratoxin A. Mycotoxin screening exists as a separate analysis because these compounds are stable and persist after the mould that produced them is gone. A batch can pass a viable microbial count and still carry mycotoxins from an earlier problem.
Applies to: flower and extracts made from it.
Heavy metal testing
Heavy metal testing screens for lead, arsenic, cadmium and mercury. Cannabis is an efficient bioaccumulator — it draws elements out of soil and water and concentrates them in plant tissue. That property is useful enough that hemp is deliberately used for soil remediation, and it is exactly why this analysis is not optional.
A heavy metal failure points at inputs: growing medium, water source, fertilisers, or in the case of vape products, the hardware itself. Cartridge components have been a recurring source of metal contamination independent of the cannabis in them.
Applies to: all cannabis products.
Pesticide analysis
Pesticide analysis screens for residues across a defined list of active ingredients, with action limits set per compound. The lists vary substantially between jurisdictions, and a product that passes in one state can fail in another on the same data.
Residues turn up for reasons beyond deliberate application. Drift from neighbouring operations, contaminated clones brought in from outside, and reused equipment all introduce compounds that were never applied to the crop on purpose.
Applies to: all cannabis products.
Residual solvent testing
Solvent-based extraction uses butane, propane, ethanol or CO₂ to strip cannabinoids from plant material. Residual solvent testing measures what is left in the finished extract after purging.
This analysis only applies to products made with solvents. Rosin, hash and other mechanically separated concentrates do not require it, though many producers run it anyway to document that.
Applies to: solvent-extracted concentrates, distillates, and products made from them.
Filth and foreign material
Filth and foreign material inspection is a physical examination for insect fragments, hair, mould visible to the eye, and anything else that does not belong. It is the least technical analysis on the panel and one of the most direct indicators of post-harvest handling.
Applies to: flower and plant material.
Where Product Type Changes the Panel
The panel is not identical across the catalogue.
- Flower carries the fullest plant-material panel: potency, microbials, mycotoxins, heavy metals, pesticides, water activity, moisture and foreign material.
- Concentrates and vapes add residual solvents and drop water activity. Contaminants concentrate alongside cannabinoids during extraction, so a pesticide level that passed in the source flower can fail in the extract.
- Edibles and beverages introduce homogeneity as the central problem. Potency has to be consistent across every unit in the batch, not merely correct on average. That is a different analytical challenge, covered in why edibles are tested differently.
- Topicals are generally tested for potency and contaminants but sit outside inhalation-specific requirements.
Reading a Result Properly
Three habits make results far more useful.
First, check what was not tested. A COA showing potency alone is not evidence of safety. Absence of a contaminant panel is not the same as a clean contaminant panel.
Second, look at limits of detection. “Not detected” means the analysis found nothing above the method’s detection threshold — not that the compound is definitively absent at zero. A laboratory that publishes its detection limits is telling you how strong that statement actually is.
Third, match the batch. A report is valid for the batch identified on it. If the batch number on the packaging does not correspond to the one on the certificate, the report is describing something else.
For a section-by-section walkthrough of an actual report, see the grower’s guide to understanding cannabis lab results. For the wider context on why these panels exist, start with what cannabis lab testing is.