Medical Cannabis Glossary — UK Patient Guide

A

Analgesic: A substance that relieves pain. Medical cannabis has analgesic properties, particularly useful for chronic pain and neuropathic pain conditions. THC and CBD both contribute to its pain-relieving effects via the endocannabinoid system.
Anxiolytic: A substance that reduces anxiety. CBD is widely studied for its anxiolytic effects, and some patients are prescribed medical cannabis for anxiety-related conditions. Dosing should be carefully titrated as high-THC products can increase anxiety in some individuals.

B

Batch Testing: The process by which each production batch of medical cannabis is independently tested by an accredited laboratory before release. Tests confirm cannabinoid potency, terpene profile, and the absence of contaminants such as pesticides, heavy metals, and microbial organisms. Results are published in the Certificate of Analysis (CoA).
Bioavailability: The proportion of a drug that enters the bloodstream and has an active effect. Inhaled cannabis via a dry herb vaporiser delivers around 30–50% bioavailability, while oral oils typically achieve 6–20% due to first-pass metabolism. Bioavailability directly affects the effective dose needed.
Broad Spectrum: A cannabis extract containing multiple cannabinoids and terpenes but with THC removed or reduced below detectable limits. Broad-spectrum products aim to provide entourage effect benefits without the psychoactive component of THC.

C

Carbon Dioxide (CO₂) Extraction: A solvent-free extraction method using pressurised CO₂ to isolate cannabinoids and terpenes from cannabis plant material. CO₂ extraction is considered a clean, pharmaceutical-grade process and is commonly used to produce medical-grade oils and concentrates in the UK.
Caryophyllene (Beta-Caryophyllene): A terpene found in cannabis, black pepper, and cloves. Uniquely among terpenes, beta-caryophyllene can bind directly to CB2 receptors in the endocannabinoid system. It has demonstrated anti-inflammatory properties and contributes a spicy, peppery aroma to certain strains.
CB1 (Cannabinoid Receptor Type 1): A receptor in the endocannabinoid system found primarily in the brain and central nervous system. THC binds strongly to CB1 receptors, producing its psychoactive effects. CB1 receptors also play a role in pain signalling, mood, memory, and appetite regulation.
CB2 (Cannabinoid Receptor Type 2): A receptor in the endocannabinoid system found mainly in immune tissues and peripheral organs. CB2 receptor activation is associated with anti-inflammatory effects. CBD and beta-caryophyllene both modulate CB2 activity, which is why cannabis may be beneficial in inflammatory conditions.
CBD (Cannabidiol): The second most studied cannabinoid in cannabis. CBD is non-intoxicating and has a wide range of therapeutic applications including epilepsy, anxiety, and pain. Epidyolex is a CBD-based medicine licensed by the MHRA for severe childhood epilepsies. CBD modulates the endocannabinoid system without directly binding to CB1 receptors.
CBDA (Cannabidiolic Acid): The acidic, raw form of CBD found in fresh and unheated cannabis. CBDA is converted to CBD through decarboxylation. Early research suggests CBDA may have anti-nausea and anti-inflammatory properties distinct from those of CBD, but clinical evidence remains limited.
CBG (Cannabigerol): Often called the "mother cannabinoid" because CBGA (its acid precursor) is the biosynthetic origin of THC, CBD, and CBC. CBG is non-intoxicating and under investigation for antibacterial, anti-inflammatory, and neuroprotective properties. CBG-dominant flower is increasingly available through UK specialist clinics.
CBN (Cannabinol): A mildly psychoactive cannabinoid formed by the oxidation and degradation of THC. Older or improperly stored cannabis tends to have higher CBN levels. CBN is often associated with sedative effects, though clinical evidence is still emerging. It is present in small quantities in most cannabis products.
CoA (Certificate of Analysis): A document issued by an independent, accredited laboratory confirming the cannabinoid content, terpene profile, and safety test results (pesticides, heavy metals, microbes) for a specific batch of medical cannabis. UK patients can request the CoA for any dispensed product from their clinic or pharmacy.
Controlled Drugs Licence: A licence issued by the Home Office permitting a company to produce, supply, or possess controlled drugs, including Schedule 2 cannabis medicines. All licensed UK medical cannabis importers and pharmacies must hold a valid Controlled Drugs Licence to legally handle these medicines.

D

Decarboxylation: The chemical process — triggered by heat — that converts inactive cannabinoid acids (e.g. THCA, CBDA) into their active forms (THC, CBD). Decarboxylation occurs automatically when cannabis flower is vaporised or smoked, or when oils are manufactured. Raw cannabis does not produce significant psychoactive effects without this process.
Dry Herb Vaporiser: A medical device that heats cannabis flower to a temperature sufficient for decarboxylation and vapour production (typically 170–210 °C), without combustion. Vaporising is considered safer than smoking as it avoids the harmful byproducts of combustion. UK clinics prescribe specific devices — such as the Mighty Medic or Volcano Medic — alongside flower prescriptions.

E

Endocannabinoid System (ECS): A complex cell-signalling system in the human body comprising endocannabinoids (naturally produced molecules), receptors (CB1 and CB2), and enzymes. The ECS plays a key role in regulating pain, mood, appetite, sleep, and immune response. Plant cannabinoids like THC and CBD interact with this system to produce therapeutic effects.
Entourage Effect: The theory — supported by growing evidence — that cannabinoids, terpenes, and other plant compounds work synergistically to produce a greater therapeutic effect than any single compound alone. This is the rationale for preferring full-spectrum extracts over isolates for certain conditions.
Epidyolex: The first plant-derived, pharmaceutical-grade CBD medicine to receive MHRA approval in the UK. Epidyolex (cannabidiol oral solution, 100 mg/ml) is licensed for Dravet syndrome and Lennox–Gastaut syndrome in patients aged 2 and over, and is available on NHS prescription. It is manufactured by GW Pharmaceuticals.

F

Flower (Cannabis Flower): The dried, harvested bud of the female cannabis plant. Medical cannabis flower prescribed in the UK is cultivated to pharmaceutical standards (EU-GMP), batch-tested, and dispensed by licenced pharmacies. It is typically administered via a prescribed dry herb vaporiser. Browse flower products.
Full Spectrum: A cannabis extract that retains all naturally occurring cannabinoids (including THC), terpenes, flavonoids, and other plant compounds. Full-spectrum products are thought to deliver a stronger entourage effect than broad-spectrum or isolate preparations.

G

GMC (General Medical Council): The regulatory body responsible for licensing and overseeing medical doctors in the UK. Only GMC-registered specialist doctors with the appropriate expertise may issue medical cannabis prescriptions in the UK. A prescription from an unregistered or non-specialist practitioner would be invalid.

H

Homeostasis: The biological process by which the body maintains stable internal conditions (temperature, pH, inflammation, pain levels, etc.). The endocannabinoid system is a key regulator of homeostasis, which is why cannabis-based medicines can have wide-ranging effects across multiple body systems.
Hybrid: A cannabis strain bred from both indica and sativa genetics. The vast majority of modern medical cannabis strains are hybrids. Effects vary depending on the cannabinoid and terpene profile rather than purely on the indica/sativa classification. Browse hybrid strains.

I

Indica: A subspecies of the Cannabis sativa plant, historically associated with shorter, bushier plants originating in Central Asia. Indica strains are commonly associated with relaxing, sedative effects. However, modern pharmacology considers the cannabinoid and terpene profile to be more clinically relevant than the indica/sativa classification.
Isolate: A purified form of a single cannabinoid — most commonly CBD isolate — extracted and processed to remove all other plant compounds. Isolates are useful when a precise, standardised dose of one cannabinoid is required and THC must be avoided entirely. They lack the entourage effect of full-spectrum preparations.

L

Linalool: A terpene found in cannabis and lavender, associated with a floral, lavender-like aroma. Linalool is researched for its anxiolytic and sedative properties, and may enhance the calming effects of certain medical cannabis preparations. It is also found in many aromatherapy products.
Limonene: A terpene common in citrus fruits and certain cannabis strains, producing a fresh, citrusy aroma. Limonene is studied for potential antidepressant, anxiolytic, and anti-inflammatory effects. It may improve the absorption of other terpenes and cannabinoids through the skin and mucous membranes.

M

MHRA (Medicines and Healthcare products Regulatory Agency): The UK government agency responsible for regulating medicines, medical devices, and blood products. The MHRA licenses cannabis-based pharmaceutical products such as Sativex and Epidyolex. Unlicensed medical cannabis products are prescribed on a named-patient basis under MHRA guidance.
Myrcene: The most abundant terpene in most commercial cannabis strains, producing an earthy, musky, herbal aroma similar to hops. Myrcene is thought to enhance the permeability of cell membranes, potentially increasing the speed of cannabinoid onset. It has reported sedative and muscle-relaxant properties.

N

Named Patient (Named Patient Programme): A regulatory framework allowing UK specialist doctors to prescribe unlicensed medicines — including most medical cannabis products — for individual patients when no licensed alternative is appropriate. The MHRA permits named-patient prescriptions under Schedule 2 of the Misuse of Drugs Regulations 2001.
Neuropathic Pain: Pain caused by damage or dysfunction of the nervous system, often described as burning, shooting, or stabbing. Medical cannabis — particularly THC-containing preparations — has the strongest clinical evidence base for neuropathic pain among its indications. It is one of the most commonly prescribed indications at UK cannabis clinics.
NICE Guidelines (NG144): Guidelines issued by the National Institute for Health and Care Excellence in November 2019 (NG144) on the prescribing of cannabis-based products for medicinal use. NICE recommends prescribing only for specific conditions (epilepsy, MS spasticity, chemotherapy-induced nausea) where evidence is sufficient, but acknowledges specialist prescribing for other conditions on a case-by-case basis.
NHS Named Patient Programme: An NHS pathway by which hospital-based specialist consultants can prescribe unlicensed cannabis medicines for NHS patients who have failed standard treatments. In practice, the vast majority of UK medical cannabis prescriptions are issued through private clinics rather than through the NHS named-patient route due to funding and administrative constraints.

O

Oil (Cannabis Oil): A liquid cannabis extract typically administered sublingually (under the tongue) or orally. Medical cannabis oils are supplied in measured-dose bottles or syringes and contain specific ratios of THC, CBD, and other cannabinoids. Onset is slower than vaporised flower (30–90 minutes) but effects last longer. Browse oil products.

P

Pinene (Alpha-Pinene): A terpene found in pine trees and cannabis strains, producing a sharp, fresh, piney aroma. Pinene is the most widely encountered terpene in nature. It may act as a bronchodilator, potentially countering some of the respiratory effects of inhaled cannabis. It is also studied for its anti-inflammatory and alertness-promoting properties.
Potency: The concentration of cannabinoids — primarily THC and CBD — in a cannabis product, expressed as a percentage of dry weight for flower, or as mg/ml for oils. Potency is confirmed by batch testing and documented in the Certificate of Analysis. New patients are generally started on lower-potency products during titration.

S

Sativa: A subspecies of Cannabis sativa, traditionally associated with taller plants and more energising, cerebral effects. As with indica, the practical therapeutic distinction between sativa and indica is considered less relevant than the cannabinoid and terpene profile. Browse strains.
Sativex (Nabiximols): The first cannabis-derived medicine to be licensed in the UK, approved by the MHRA in 2010 for spasticity in multiple sclerosis. Sativex is an oromucosal spray containing equal parts THC and CBD (2.7 mg THC + 2.5 mg CBD per spray). It is manufactured by GW Pharmaceuticals and available on NHS prescription for qualifying MS patients.
Schedule 2 (Misuse of Drugs Regulations 2001): The legal classification under which most medical cannabis products (with more than 1 mg THC) are regulated in the UK. Schedule 2 drugs have recognised medical uses but require strict controls over production, supply, prescription, and record-keeping. This reclassification from Schedule 1 in November 2018 enabled specialist doctors to prescribe medical cannabis legally for the first time.

T

Terpene Profile: The unique combination and concentration of terpenes present in a specific cannabis strain or batch. Terpene profiles vary between strains and between batches of the same strain, influencing aroma, flavour, and potentially therapeutic effects. Profiles are documented in the Certificate of Analysis.
Terpenes: Aromatic organic compounds found throughout the plant kingdom, including in cannabis. Cannabis contains over 150 different terpenes, including myrcene, limonene, linalool, pinene, and caryophyllene. Terpenes contribute to the aroma and taste of cannabis and may influence its therapeutic effects through the entourage effect.
THC (Tetrahydrocannabinol): The primary psychoactive cannabinoid in cannabis. THC binds to CB1 receptors in the brain, producing the characteristic "high" as well as therapeutic effects including pain relief, appetite stimulation, and anti-nausea. Medical cannabis products are classified as Schedule 2 in the UK when they contain more than 1 mg of THC.
THC:CBD Ratio: The proportion of THC to CBD in a cannabis product, e.g. 20:1 (high THC, minimal CBD) or 1:1 (balanced). The ratio influences both therapeutic effect and side-effect profile. Higher CBD proportions may moderate some psychoactive effects of THC. Specialists consider the THC:CBD ratio carefully when selecting a product during titration.
THCA (Tetrahydrocannabinolic Acid): The acidic, inactive precursor to THC, naturally present in raw and unheated cannabis. THCA is non-intoxicating until converted to THC via decarboxylation. Early research suggests THCA may have anti-inflammatory and neuroprotective properties in its own right, independent of THC conversion.
Tincture: A liquid cannabis extract dissolved in alcohol or another solvent, typically administered sublingually. Medical-grade cannabis tinctures are less common in the UK than oil formulations but are available through some specialist pharmacies. Onset time and bioavailability are similar to cannabis oils.
Titration: The process of gradually adjusting a patient's cannabis dose over time to find the minimum effective dose with the fewest side effects. UK specialists typically start patients on a low dose and increase slowly — often over weeks — monitoring symptom response and tolerability at each stage. Titration is a key principle of safe medical cannabis prescribing.
Tolerance: A reduction in response to a drug after repeated use, requiring a higher dose to achieve the same effect. Cannabis tolerance is primarily driven by downregulation of CB1 receptors in response to regular THC exposure. Planned tolerance breaks (periods without cannabis) can help restore sensitivity. Tolerance to CBD is less well documented.

U

Unlicensed Medicine: A medicine that has not received a marketing authorisation (licence) from the MHRA for a specific indication. The majority of medical cannabis products prescribed in the UK are unlicensed and issued under the named-patient framework. Prescribers take personal responsibility for the clinical appropriateness of unlicensed prescriptions.

V

Vaporiser (Vaporizer): See Dry Herb Vaporiser. A device that heats cannabis to produce an inhalable vapour without combustion. UK clinics typically prescribe a specific pharmaceutical-grade device alongside flower prescriptions. The Storz & Bickel Volcano Medic 2 and Mighty Medic are commonly prescribed models.