Patient resource
How to read a medicinal cannabis flower COA
A certificate of analysis can help you understand what was measured in a particular batch of flower. Start with the batch number, then read the results, units and gaps. The certificate is one piece of information to discuss with your pharmacist or prescriber.
The first check: does it match your tub?
Find the batch or lot number on your product label and compare it with the number on the COA. The product name alone is not enough: the next batch can have different measured results.
Check the identity
Look for the product name, flower or dried-flower description, batch/lot or sample code, report date and who issued the report. A sample code may need the brand to confirm which retail batch it maps to.
Check what kind of report it is
A potency report, a terpene report and a finished-product release COA answer different questions. A single page headed “Certificate of Analysis” may cover only one test panel.
Read it in six steps
Learn with a sample report. Explore a fictional flower COA, select each test category and practise matching the batch number.
Open interactive COA ↗Match the batch and dates
Compare the lot number on your container with the COA. Check when the sample was received, tested or released, and whether the report is a current version. If the link shows an older batch, ask for your batch’s report.
Read the cannabinoid units
Flower results may appear as % by weight or mg/g. For flower, 1% by weight = 10 mg/g, so 24.5% equals 245 mg/g. Check whether the report uses an “as received” or dry-weight basis before comparing figures across reports.
Separate THCA from THC
Unheated flower often contains much more THCA than delta-9 THC. Heat can convert some THCA to THC. When the lab uses the common potential-THC calculation, it shows:
Total potential THC = delta-9 THC + (THCA × 0.877)
For example, 27.55% THCA and 0.33% delta-9 THC give approximately 24.5% total potential THC. This estimates chemical potential, not the amount absorbed by a person. Read the lab’s own calculation and definitions.
Look at the terpene profile
An individual terpene percentage is its share of the flower’s weight, not its share of the terpene total. A result of 0.71% beta-caryophyllene means about 7.1 mg per gram of flower. “Total terpenes” usually adds the compounds measured and reported by that method. A higher total is not a proven measure of quality, safety or treatment effect.
Read contaminant results and limits
Look for the named tests, results, methods and acceptance limits. Relevant panels may include pesticides, heavy metals, mycotoxins, microorganisms, foreign matter and total ash. “Pass” means the reported result met the stated criterion; it does not mean every possible contaminant was tested or that the level is zero.
Notice what is missing
A report may omit terpenes, full pesticide analytes, microbial detail or the finished-product release decision. “Not detected” applies only to the named substance and method at its detection limit. “Not tested” gives no result. If a section is absent, ask whether another report or batch-release document covers it.
Common terms in plain English
| Term | What to read it as |
|---|---|
| ND / not detected | The lab did not detect that named substance using the stated method. It does not mean absolute zero. |
| NT / not tested | There is no test result for that item. |
| LOD / LOQ | The method’s detection / reliable quantification limits. The report legend should explain its exact convention. |
| NMT / specification | “Not more than” / the acceptance limit used to judge a result. |
| % w/w | Percentage by weight. For flower, 1% w/w is 10 mg/g. |
| CFU/g | Colony-forming units per gram, used for some microbial counts. |
What about plant growth regulators?
“PGR” is a broad term for plant growth regulators, not the name of a single substance or a universal laboratory test. Do not infer “PGR-free” from a general pesticide pass or from a COA that says nothing about PGRs.
Chemical names you may want to look for or ask about include paclobutrazol (PBZ), daminozide (sometimes called Alar) and chlormequat chloride. These are examples of specific growth-regulating chemicals, not a complete list and not evidence that they were used in your product. Paclobutrazol and daminozide appear on Canada’s cannabis pesticide testing list; that list does not define Australian testing requirements.
Find the named analyte list for your exact batch, then check each result and its reporting limit. A general “pesticides: pass” row may not show whether any of these substances was included. A missing name means the public report does not answer the question; it does not prove that the substance was present, absent or untested.
What do we know about harm?
A controlled study of cannabis deliberately spiked with pesticides found that paclobutrazol residue could transfer into smoke, which shows a possible route of exposure.
IARC reports that 1,1-dimethylhydrazine, a breakdown product of daminozide, is possibly carcinogenic to humans (Group 2B), based on animal evidence. The US EPA IRIS entry for paclobutrazol has no cancer assessment.
Human cancer risk from these residues in cannabis remains uncertain; however, we should do our best to avoid products grown with PGR's until we know more about their effects on humans.
For community context, see Friendly Aussie Buds’ PGR article to see what flower treated with PGR's may look like. For testing context and primary evidence, use the linked Health Canada list, smoke-transfer study, IARC report and EPA assessment.
Australian products, overseas reports
Many Australian medicinal cannabis products are imported, so a COA may come from a laboratory overseas. Its layout, units, analyte list, accreditation and wording may differ from an Australian report.
Australian requirements still apply to products supplied here. The TGA’s medicinal cannabis standard, TGO 93, sets minimum quality requirements for products imported into or supplied in Australia; the Australian sponsor is responsible for conformity. Overseas manufacturing must meet specified good manufacturing practice (GMP) requirements. GMP describes manufacturing controls; it is not the same thing as a laboratory’s ISO/IEC 17025 accreditation.
A public lab report may show only part of the quality evidence. The TGA permits justified reduced or rotational testing for some plant tests, so a missing row does not automatically prove that a product is non-compliant. Ask the sponsor or pharmacist what evidence covers the batch. Most medicinal cannabis products supplied through special access are unapproved medicines; a COA does not turn them into TGA-approved products.
How to find your batch’s COA
- Write down the product name and batch/lot number on your container.
- Check Catalyst for available product and batch information. Access to detailed documents can depend on account type.
- If you cannot find the exact batch, ask your pharmacist or email the brand/sponsor for the relevant COA and any separate terpene, pesticide or batch-release reports.
If the batch number does not match, the report is unclear, or the measured result worries you, discuss it with your dispensing pharmacist or prescriber before changing how you use your medicine.