European Pharmacopoeia monograph 3028 on cannabis flower took effect on 1 July 2024, and every member state had to retire its national monograph in its favour. If you have shipped into the EU since then and watched an importer's laboratory report a total THC figure that does not match your certificate of analysis, that monograph is usually the reason.
EU cannabis retesting is the import control that requires a batch from a third country to be re-analysed inside the EU before a Qualified Person can certify it for release. The Canadian number and the European number diverge because the two laboratories run different pharmacopoeial methods, express results on different moisture bases, and measure the flower weeks apart in its chemical life.
That gap is not a quality failure. Handled badly, it turns into one.
Why an EU importer retests a batch you already tested
Article 51(1)(b) of Directive 2001/83/EC is the whole answer. Any production batch arriving from a third country has to undergo, within a Member State, a full qualitative analysis and a quantitative analysis of at least all active substances, plus whatever further checks the quality of the product requires. Your Montreal certificate of analysis is supporting evidence. It is not the analysis the law asks for.
The person who carries that obligation is the importer's Qualified Person, working under EU-GMP Annex 16. The QP signs a register entry that puts their own licence behind the batch. No QP signs that entry on a supplier document from outside the EU, however good the supplier is. Our guide to what the Qualified Person actually certifies walks through the rest of the file they build.
The mutual recognition route, and why it rarely helps
Article 51(2) does allow a QP to rely on third-country controls where a mutual recognition agreement is in place, and Canada does hold a GMP mutual recognition agreement with the EU. Read the sectoral annex before you plan around it. The waiver runs on defined product categories and on a GMP certificate issued by the exporting authority, and a licence issued under the Cannabis Act is not a drug establishment licence issued under the Food and Drugs Act.
Ask the importer's QP, in writing, whether they intend to rely on the MRA for your flower. Most will tell you they do not. Plan the shipping calendar around a full EU retest and treat any waiver as a bonus, because the retest is not the importer doubting your work. It is the only route their QP has to a signature.
Four reasons the retest number lands somewhere else
A Canadian result and a European result on the same flower are both correct and still different. Four mechanisms account for most of the spread, and they do not cancel each other out.
Moisture basis
Monograph Ph. Eur. 3028 expresses cannabinoid content on the dried drug, with a loss on drying determination applied to the raw assay. Canadian certificates commonly report the figure as received, at whatever moisture the flower held on test day. The same material can read a point or more apart depending only on which convention the report follows.
Calibration approach
Ph. Eur. 3028 quantifies THC, THCA, CBD, CBDA, CBN and CBNA against one certified reference material, cannabidiol, applying a published response correction factor to each analyte and a molecular mass factor to convert each acid into its neutral equivalent. The German pharmacopoeia text it replaced used a separate reference standard per cannabinoid across a multi-point calibration curve, and most Canadian laboratories work the same way. Two defensible methods, two slightly different answers. If you are unclear on how the acid and neutral forms combine, our explainer on how total THC is calculated and labelled covers the arithmetic.
Time and temperature in transit
THCA converts toward THC, and THC oxidises toward CBN. Flower assayed in Montreal in March and reassayed in Frankfurt in May is not chemically identical to itself. The Ph. Eur. revision circulated for consultation in Pharmeuropa 37.4, with comments closing on 31 December 2025, widened the HPTLC acceptance criterion for the THC zone. The reason is the same chemistry. THC-dominant flower tested soon after drying can show a free THC zone that is faint or absent, because the THC has not formed yet.
Independent sampling
The importer draws its own sample from the shipped units under its own plan. You sampled a homogenised release lot at your facility. Flower is not uniform, and two honest sampling plans on the same pallet will not produce the same composite.
| Divergence point | Typical Canadian practice | Ph. Eur. 3028 practice | Effect on the reported figure |
|---|---|---|---|
| Moisture basis | As received | Dried drug, loss on drying applied | EU figure reads higher |
| Calibration | Analyte-specific standards, calibration curve | Single CBD reference, correction factors | Small shift either way |
| Time of test | At release, pre-shipment | On arrival, weeks later | THC up, THCA down, CBN up |
| Sampling | Homogenised release lot | Importer's own plan from shipped units | Adds spread in both directions |
A release specification that says nothing more than total THC by in-house HPLC is not an export specification. It is a domestic one. Each mechanism above moves the number a little. Stacked, they move it past the tolerance, and the tolerance is what the QP is really testing against.
The 10 per cent rule that decides whether a batch passes
Ph. Eur. 3028 sorts cannabis flower into three types by content on the dried drug. THC-dominant material carries a minimum of 5.0 per cent total THC and a maximum of 1.0 per cent total CBD. CBD-dominant material inverts those figures. Intermediate material sits at a minimum of 1.0 per cent for each. Those bands decide which type your batch is, but they are not what fails shipments.
What fails shipments is the content criterion. Where the flower will be prescribed to a patient as a medicinal product, total THC and total CBD have to fall within 10 per cent of the labelled content. Where the same flower goes in as a raw material for extraction, that tighter criterion does not apply, because downstream processing controls the potency of the finished product anyway. One batch, two different acceptance regimes, decided entirely by what the importer does with it next.
Ten per cent is narrow once you put the four divergence points beside it. For comparison, Australia's TGO 93 has operated on a wider 20 per cent deviation, which is why a batch record assembled for Australian supply does not transfer cleanly to a European release. We set out where else the specifications part company in our comparison of release requirements across four export markets.
Where LPs quietly lose batches
The label claim is the trap. Print your own assay result to one decimal place on the batch document and you have set a target with no headroom, then handed the tolerance calculation to a laboratory running a different method on older flower. When that calculation goes the wrong way, you are into the process we set out on what happens when a batch is rejected at import. A declared 24.6 per cent leaves a band of 22.1 to 27.1. A declared 24 per cent leaves 21.6 to 26.4. The difference between those two decisions is the difference between a release and a hold, and it costs nothing to make correctly at the front end.
The monograph also carries the identification tests, foreign matter limits and contaminant limits that sit alongside content, read together with the general monograph on herbal drugs. Potency is simply where the arguments happen, because it is the only figure both sides print.
Closing the gap before the pallet leaves Montreal
None of this requires a new facility. It requires the release package to be built for the laboratory that will check it, which is a decision about specifications and paperwork rather than equipment.
- Test to the monograph, not only to the Cannabis Act. Ask whether your ISO/IEC 17025 accredited laboratory can run Ph. Eur. 3028, including loss on drying and the correction factor calculation, and have it report both the as-received and dried-drug figures on the same certificate. If you have not checked the scope on its accreditation certificate, our guide to verifying a cannabis laboratory's accreditation shows what to look for.
- Set the label claim with headroom. Declare a rounded content the batch can still hold at both ends of the 10 per cent band after several weeks in transit, rather than the assay result to one decimal place.
- Write the method into the contract. Name the monograph, the moisture basis, the sampling plan, the out-of-specification route and who funds a confirmatory third-laboratory test. Our guide to the quality agreement between a Canadian LP and an EU importer covers the clauses that matter.
- Send the raw data with the certificate. Chromatograms, system suitability results and reference standard certificates let a QP reconcile two numbers in an afternoon instead of opening a deviation.
Keep retention samples from the same homogenised lot, and keep the release-to-departure window short. A batch that sits four weeks in a Canadian vault before it flies has already spent part of its tolerance before anyone in Europe opens the carton.
AlphaLeaf is a Health Canada Licensed Producer in Montreal, growing indoor, hand-trimmed flower from refined genetics with full batch traceability. We hold export authorisation under the Cannabis Act and build release documentation, ISO/IEC 17025 batch data and retention samples around what a European importer's Qualified Person has to certify, rather than around what is convenient at our end.
Two laboratories will rarely print the same number, and nobody in the chain expects them to. What the Qualified Person needs is a specification, a method and a data package that make the difference explainable before the batch lands. Build that and the retest is a formality. Skip it and it is a hold. Talk to our export team about the release specification your importer's QP will sign against.
Frequently Asked Questions
Does an EU importer have to retest Canadian cannabis flower?
In almost every case, yes. Article 51(1)(b) of Directive 2001/83/EC requires each batch arriving from a third country to undergo a full qualitative analysis and a quantitative analysis of at least all active substances inside a Member State before a Qualified Person certifies it. The importer's own laboratory result, not the Canadian certificate of analysis, is what the QP certifies against.
Why is the EU retest THC result different from our Canadian COA?
Four mechanisms account for most of it. Ph. Eur. monograph 3028 expresses content on the dried drug while Canadian certificates commonly report as received. The monograph quantifies cannabinoids against a single cannabidiol reference standard using correction factors rather than analyte-specific calibration curves. Acidic cannabinoids keep converting during transit. And the two laboratories sample independently. Each shifts the figure slightly, and they stack.
What is European Pharmacopoeia monograph 3028?
It is the Ph. Eur. quality standard for cannabis flower. It was adopted in June 2023, published in Ph. Eur. Supplement 11.5 in January 2024 and took effect on 1 July 2024, replacing national monographs such as the German pharmacopoeia text across member states. It sets the identification tests, cannabinoid content criteria, foreign matter limits and contaminant limits an EU importer tests a batch against.
Does the Canada-EU mutual recognition agreement remove EU retesting for cannabis?
Do not assume it does. The MRA's GMP annex waives import testing only within its defined product scope and on the strength of a GMP certificate issued by the exporting authority. A Cannabis Act licence is not a Food and Drugs Act drug establishment licence, so the waiver does not automatically reach dried cannabis flower. Confirm the position with your importer's Qualified Person in writing before planning a shipping schedule around it.
What content tolerance applies to total THC under Ph. Eur. 3028?
Where cannabis flower is prescribed to patients as a medicinal product, total THC and total CBD must fall within 10 per cent of the labelled content. Where the flower is supplied as a raw material for extraction, that tighter criterion is not applied. Australia's TGO 93 has operated on a wider 20 per cent deviation, so an Australian batch record does not automatically satisfy a European release.
Can an EU importer reject a batch on the retest result alone?
Yes. If the retest puts total THC or total CBD outside the labelled content tolerance, or outside any other limit in the monograph, the Qualified Person cannot certify the batch and it will not be released. Whether it can then be relabelled, returned or destroyed depends on your supply agreement, the importer's narcotics licence conditions and the receiving authority.
