PatientsCann UK · Patient education
From Seed to Patient: the UK medical cannabis pipeline
Every legal prescription in the UK travels the same route: a controlled growing room, a licensed factory, an accredited laboratory, a border, a specialist clinic and a pharmacy. This explorer walks you through all six stages, compares the seven formats a patient can be prescribed, and shows you how to read the paperwork that proves it.
This is education, not medical advice. Onset and duration figures are typical ranges reported for each route. Your own response depends on your dose, your product and your body. Never change how you take your medicine without speaking to your prescriber or pharmacist. See all patient resources
The six stages of a legal UK prescription
Select any stage to open the detail. Each one has its own quality standard and its own regulator, and a batch cannot move forward until the stage before it has been signed off.
Genetics, breeding and GACP cultivation
Where the medicine starts: a known plant, grown the same way every time.
A licensed grower keeps a small number of mother plants and takes cuttings from them, often through tissue culture, so that every crop is genetically the same plant rather than a new cross. Growing rooms are closed loop: light, temperature, humidity, carbon dioxide and air filtering are all controlled and logged.
- Mother plant care and cutting or tissue culture cloning
- Batch to batch genetic stability, checked crop by crop
- Sealed rooms with filtered air and monitored water feeds
(Good Agricultural and Collection Practice). It sets how the plant is grown, fed, harvested and handled. In practice it means no synthetic pesticides, and soil, water and fertiliser chosen so the plant does not draw heavy metals up into the flower. Where the flower is dispensed as it is, GACP alone is not enough: the maker has to write down the point at which production of the begins, and for whole flower that point is the growing room.
in the UK, alongside the agricultural inspectors of the country the crop is grown in. Growers are inspected and have to keep records for every batch they release.
One decision sets the whole rulebook
What the crop is going to become decides where pharmaceutical rules start. It is the single most important point in the chain, and the one most often got wrong.
The plant is the active substance
Nothing downstream can purify or sterilise a dried bud, so quality has to be built in from the cuttings onward. recognises that manufacture can begin at propagation.
The plant is a starting material
Here quality is defined later. Extraction, filtering and purification can take impurities out, so the plant is grown under and pharmaceutical rules begin at the processing step.
A prescription only works as medicine if the next jar behaves like the last one. Controlled genetics and controlled rooms are what let a pharmacist put a fixed cannabinoid percentage on a label. Illicit supply has none of this: the same street name can be a different plant, grown a different way, with a different strength every time, and nobody has tested it.
Pharmaceutical processing and GMP extraction
The crop becomes a pharmaceutical product in a cleanroom.
Harvested flower is dried and cured at a set temperature and humidity, then milled to a controlled particle size for vaporising. For oils and cartridges the plant material goes through supercritical carbon dioxide extraction, then winterisation to strip out fats and waxes, with any solvent recovered and accounted for.
- Controlled drying, curing and precision milling
- Cold carbon dioxide extraction under pressure
- Winterisation, filtration and solvent recovery
- Standardising the extract to a fixed cannabinoid strength
EU and UK (Good Manufacturing Practice). Work happens in cleanrooms with ISO class 5 and class 7 air handling and positive air pressure, so air always flows out of the clean space rather than into it. Every step is written down, signed and traceable to the batch. The rulebook is EudraLex Volume 4: Part I for finished medicines, Part II for active substances, and for medicinal cannabis intended for use as whole flower. sits across all of it.
The , the UK medicines regulator. A site that makes or releases a medicine for UK patients has to hold and keep its GMP certification through inspection.
Three routes out of the same growing room
Where GACP stops and GMP starts depends on what the batch is going to become. Requirements tighten at every step closer to the patient.
Sold on as feedstock, so the later GMP steps happen at another site.
Processing can remove impurities, so the finished extract is standardised before it is filled.
Covered end to end by GMP Annex 2. The flower itself is the finished medicine, so nothing can be cleaned out of it later.
GACP covers the plant. GMP covers the medicine. That is the real difference between a crop and a prescription: in a GMP site nothing moves without a batch record, and if a problem is found later the batch can be traced back and recalled.
Analytical testing and the Certificate of Analysis
An independent laboratory decides whether the batch is fit to release.
Samples are taken from across the batch and tested in stages. measures how much of each cannabinoid is present. identifies the smaller compounds, including terpenes and anything left behind by processing.
- Cannabinoid profile: delta-9-THC, CBD and CBG percentages, against a set tolerance
- Terpene content, measured rather than estimated
- Heavy metals: lead, cadmium, mercury and arsenic
- Microbiology: E. coli, salmonella and aspergillus
- Mycotoxins, the poisons some moulds leave behind
- Residual solvents from extraction
accredited laboratories. Accreditation covers the method, the equipment and the people, so the same sample tested twice gives the same answer. The results are written up as a , and the batch is not released until they pass.
Tab 3 of this explorer contains a mock Certificate of Analysis you can click through, test panel by test panel, to see what each result actually tells a pharmacist.
Controlled importation and border security
Most UK medical cannabis is imported, and every batch needs its own licence.
The batch travels as a controlled drug. Temperature is monitored and held between 15 and 25 degrees Celsius, packaging is tamper evident, and the shipment is held in secure pharmaceutical storage at each handover point rather than in ordinary freight.
- Monitored temperature for the whole journey
- Tamper evident seals, checked on arrival
- Secure vault storage in transit and named handovers
Two, not one. An export authorisation from the country the batch leaves, and a Home Office controlled drug import licence for that individual batch coming into the UK. A licence covers one shipment, so this step repeats every time.
The Home Office Controlled Drugs Licensing Unit and UK Border Force, working to the Misuse of Drugs Regulations. Paperwork that does not match the shipment stops the shipment.
Per batch licensing is one of the reasons a named product can be out of stock for weeks even when it exists in a warehouse abroad. Nothing can be shipped early or held in bulk without the licence being in place first.
Specialist prescribing and clinical governance
Only a specialist doctor can start a UK medical cannabis prescription.
You are assessed by a doctor on the specialist register, not by a general practitioner. Your history is then reviewed by a , which agrees whether a cannabis based medicine is reasonable for you and records why.
- Specialist consultation and full history
- Multi-disciplinary team review of the case
- Evidence that at least two licensed treatments were tried first, without enough relief or with side effects you could not live with
- Agreed starting dose, review dates and safety advice
A controlled drug prescription, usually issued electronically as an . It names the exact product, strength and quantity, and it is only valid for the person named on it.
The for the doctor, the for the clinic, and NICE guidance for the treatment decision itself.
The clinic notes, the team review and the prescription are what make your possession lawful. That is why we ask patients to keep their clinical letter and dispensing label with their medicine. Our verification guidance sets out exactly what to carry.
Pharmacy dispensing and the journey to your door
The last checks happen at a specialist pharmacy, not at the clinic.
The original prescription reaches a registered pharmacy that is set up to handle controlled drugs. Stock is kept in a Home Office approved safe. A registered pharmacist makes the final clinical check, labels the medicine for you by name, and releases it.
- Prescription received and validated against the register
- Storage in approved safe custody
- Final pharmacist check and patient specific labelling
- Tracked delivery by a licensed secure courier, signed for
Your name, the product, the strength, the quantity, the dose instructions, the pharmacy details and the dispensing date. That label is the single most useful thing you can show if you are ever asked to prove your prescription.
The registers and inspects the pharmacy and the pharmacist. Controlled drug records are auditable, and every dispensed quantity has to reconcile.
From cutting to courier, every step above is licensed, recorded and inspectable. Keep your medicine in its original container with the label attached, and you are holding the end of that chain.
Seven formats a UK patient can be prescribed
Filter by how quickly a format works, how long it lasts, and whether it is inhaled. Open any card for the full detail on how it is taken, how the body absorbs it, and when a clinician would choose it.
Showing all 7 formats.
Whole flower (Flos)
Dried, milled cannabis flower, prescribed to be vaporised in a medical device. Never smoked.
Through a UKCA or CE marked medical dry herb vaporiser, such as the Volcano Medic 2 or the Mighty Plus Medic. The flower is ground, loaded and heated to a set temperature so the active compounds come off as vapour. The device moves hot air through the flower without setting it alight, which is closer to a nebulised inhaler than to smoking.
Smoking or combustion is not a prescribed route. It is unlawful in most public settings, it destroys part of the medicine, and it puts tar and combustion products into your lungs.
Absorption happens in the lungs, straight into the bloodstream. Onset is 1 to 5 minutes, the peak effect is usually felt at 15 to 30 minutes, and it wears off over 2 to 4 hours.
For symptoms that need relief now: breakthrough pain, a spasm, sudden nausea. The fast onset also makes it easier to feel where your own limit is, because you are not waiting an hour to find out.
A dirty vaporiser wastes medicine and tastes wrong. Our step by step cleaning and use guides cover both desktop and portable devices.
Metered extract vape cartridges
Pre filled cartridges of distillate or solventless rosin, used with a temperature controlled battery.
The cartridge screws onto a battery designed for it and heats a measured amount of oil per draw. Nothing to grind, weigh or pack, and the strength of the oil is fixed and printed on the batch.
Through the lungs, as with flower. Onset is 1 to 3 minutes and effects last around 2 to 3 hours, slightly shorter than vaporised flower for most people.
When a patient needs fast relief but cannot manage the preparation a flower device needs, or wants something discreet and portable for use away from home.
Illicit cartridges have been linked to serious lung injury from thickening agents and cutting oils. A prescribed cartridge comes with a batch number and a Certificate of Analysis behind it.
Whole plant and distillate oils
Measured liquid extract, held under the tongue before swallowing. The usual baseline medicine.
A graduated pipette or oral syringe measures the dose in millilitres. The oil is placed under the tongue and held there for 60 to 90 seconds, then swallowed.
Two routes at once. Part of the dose crosses the lining under the tongue straight into the bloodstream, and the rest is swallowed and absorbed through the gut. That is why onset is spread over 30 to 90 minutes and cover lasts 6 to 8 hours.
As steady background cover through the day or overnight, often alongside an inhaled format kept for flare ups. Doses can be adjusted in small steps.
Because onset is slow and uneven, taking a second dose too soon is the most common way patients end up with more effect than they wanted. Wait the full time your clinic advises.
Capsules and pastilles
Pre measured solid doses, swallowed. The longest cover of any format, and the slowest to arrive.
Swallowed whole with water, like any other capsule. Nothing to measure and nothing to hold under the tongue, which suits patients with tremor, poor grip or low vision.
Through the gut, then through the liver before it reaches the rest of the body. That first pass through the liver turns some delta-9-THC into , a stronger and longer lasting compound. Onset is 60 to 120 minutes and effects can last 6 to 10 hours.
For overnight symptom cover, or for patients who need a fixed dose they cannot get wrong. Food changes absorption, so clinics usually advise taking it the same way each time.
The same milligrams swallowed can feel stronger than the same milligrams inhaled, and arrive two hours later. Start low, and never stack doses while you are waiting.
Solventless extracts: hash and rosin
Concentrate made from the flower itself by sieving or pressing, with no solvent used. Vaporised, never smoked.
Hash is made by separating the resin glands from the flower, either dry sieved or washed in ice water, then pressed. Rosin is made by pressing flower or washed hash with heat and pressure so the resin flows out. Neither uses a chemical solvent, so there is nothing to purge afterwards.
In a vaporiser or insert rated for concentrates, usually a small measured amount on a pad or in a dosing capsule. Check your device instructions: a dry herb chamber is not always suitable. As with flower, combustion is not a prescribed route.
Through the lungs, the same route as flower. Onset is 1 to 5 minutes, the peak is usually 15 to 30 minutes, and the effect lasts 2 to 4 hours.
When a patient needs a higher dose than flower can comfortably deliver, or fewer inhalations for the same relief. Also chosen by patients who want a product made without any solvent step.
A concentrate can be several times the strength of the flower it came from. Dose by the amount your clinic sets, not by eye, and expect a much smaller quantity to do the same job.
Standardised oromucosal spray
A metered spray to the inside of the cheek or under the tongue, at a fixed licensed strength.
One measured spray at a time, directed at the inside of the cheek or under the tongue, alternating sides. Nabiximols, sold as Sativex, is the example most UK patients meet.
Directly through the lining of the mouth, so less of the dose has to pass through the gut and liver. Onset is 15 to 40 minutes and effects last 4 to 6 hours.
Where a licensed product with a fixed one to one ratio of delta-9-THC to CBD is wanted for a specific condition. Because it is a licensed medicine, prescribing sits on a different footing to unlicensed cannabis products.
Most UK medical cannabis is prescribed as an unlicensed special. A licensed product like this one has been through a full medicines approval for named indications.
Suppositories and pessaries
Solid inserts used when the mouth and lungs are not an option, or when relief is needed in the pelvis.
Inserted rectally or vaginally, following the instructions from your pharmacy. They are usually stored cool so they hold their shape.
Through the veins in the lower bowel or the vaginal wall, which largely bypasses the first pass through the liver. Onset is 15 to 30 minutes and effects last 4 to 8 hours.
When swallowing or inhaling is not possible: severe nausea and vomiting, a gut that is not absorbing, or after surgery. Also used for pelvic pain, including endometriosis, where local effect is the point.
Few UK clinics raise this route unprompted. If eating and inhaling are both difficult for you, it is a reasonable thing to ask your prescriber to consider.
All seven formats on one timeline
Dashed is the wait. Solid is the expected effect. The axis runs from taking the dose to twelve hours later.
No formats match that search. Clear the box or choose a different filter.
Quality and science inspector
Two tools. First, a mock Certificate of Analysis you can click through panel by panel. Second, a timeline that puts the four main routes side by side so you can see how differently they behave in the body.
EXAMPLE DOCUMENT · NOT A REAL BATCH · FIELDS REDACTED
Onset against duration, by route
The dashed section is the wait before you feel anything. The solid bar is roughly how long the effect lasts. Select a route to read the figures.
Many patients are prescribed two formats: a slow one for baseline cover and a fast one for flare ups. Select a route above to see what that route is usually for. Your own timings also shift with how recently you ate, how deeply you inhale and how long you hold it, and the temperature your device is set to.
Who writes the rules, and who enforces them
No single body decides what a medicine has to be. Three layers sit on top of each other, and the UK layer is the one that inspects the site your prescription came from.
World Health Assembly resolution WHA 67.20 commits member states to strong medicines regulation. The WHO publishes good manufacturing practice guidance in its Technical Report Series, and rates national regulators with its Global Benchmarking Tool. Its guidance matters most in countries with no regulator of their own.
The International Council for Harmonisation turns that baseline into guidelines regulators can adopt word for word, so a medicine made in one country can be trusted in another. Its 2008 goal was one quality system covering the whole life of a product, built on risk management and science. The idea underneath is : build quality in, rather than test for it at the end.
UK GMP is built on ICH Q7 and enforced by the , the UK's . Other countries do the same through their own regulators, which is why an inspection abroad can be recognised here.
Standards referenced on this page: GACP and EU or UK GMP for growing and manufacture, ISO/IEC 17025 for laboratories, Home Office controlled drug licensing for import, and GMC, CQC, GPhC and NICE guidance for prescribing and dispensing.
