Medicinal Cannabis NZ Guide

CBD and THC explained

CBD and THC explained. Compare pharmacology, impairment and regulatory treatment. The page must give the reader a usable method, checklist or decision rule, not

If you are looking into medicinal cannabis in New Zealand, the first thing to untangle is the difference between CBD and THC. They come from the same plant, but they are not interchangeable. This guide explains what they are, how they behave in the body, how New Zealand law treats them, and gives you a practical decision rule for talking to a prescriber.

How they work

THC (delta-9-tetrahydrocannabinol) binds strongly to CB1 receptors in the central nervous system. That binding produces the euphoria, sedation, and appetite stimulation. CBD, by contrast, has a low affinity for CB1 and CB2 receptors. It appears to modulate the endocannabinoid system indirectly, and much of its clinical interest comes from anti-inflammatory, anxiolytic and anticonvulsant activity. The NZ Formulary and Healthify (2024) describe CBD as non-intoxicating at typical prescribed doses, while THC is the main psychoactive compound; a product labelled 10:10 contains 100 mg/g THC and 100 mg/g CBD.

What actually happens when you take them

Onset and duration depend on the form, not the molecule:

  • Inhaled (flower or vape): onset 5-10 minutes, peak around 30 minutes, duration 2-4 hours. This suits acute episodes (breakthrough pain, nausea, panic) because you can titrate in near real time.
  • Oral (oils, capsules): onset 30-120 minutes, duration 6-8 hours. This suits baseline symptoms, sleep, or all-day pain control.
  • Sublingual (oils held under the tongue): onset 15-30 minutes, duration 4-6 hours. This is a middle ground, but the user must hold the oil for 60-90 seconds before swallowing.

Bioavailability differs by route: inhaled THC is roughly 25-30%, oral THC is roughly 10-20% because of first-pass liver metabolism (NZ Formulary, 2024). CBD behaves differently: oral CBD has low and variable bioavailability (~6% in some pharmacokinetic studies), but it has a longer half-life than THC, so effects accumulate over days (Healthify, 2023).

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What CBD and THC actually are

Cannabis contains more than 100 cannabinoids, but two dominate prescribing decisions: CBD (cannabidiol) and THC (delta-9-tetrahydrocannabinol).

  • THC is the main psychoactive compound. It binds strongly to CB1 receptors in the brain, which is why it produces the “high” and can relieve pain, stimulate appetite, and reduce nausea. It is measured in milligrams per gram (mg/g) or as a percentage.
  • CBD is not psychoactive in the way THC is. It interacts with several receptor systems and is used mainly for anxiety, inflammation, and seizure disorders. It is also measured in mg/g or %.

A third compound, CBDA (cannabidiolic acid), is the raw precursor to CBD and appears in unheated extracts. Terpenes (myrcene, limonene, pinene) are aromatic compounds that modify the effect of cannabinoids; they are listed on some product labels but are not regulated as active ingredients.

The single most useful question is not “is it CBD or THC?” but “what is the THC:CBD ratio, and what is the route?” That ratio and the form determine the experience more than any other variable.

What is the Medicinal Cannabis Scheme?

New Zealand’s Medicinal Cannabis Scheme is the legal framework that allows a medical practitioner to prescribe a manufactured cannabis product. It is administered by the Medicinal Cannabis Agency, which sits within Medsafe, and operates under the Misuse of Drugs Act 1975 (New Zealand Ministry of Health, 2020). The scheme does not create a general licence to possess or use cannabis. It creates a prescription pathway.

Since 1 April 2020, the scheme has allowed products that meet GMP standards to be prescribed and dispensed through pharmacies. The Misuse of Drugs (Medicinal Cannabis) Regulations 2019 set out how the scheme works. The Ministry of Health’s Medicinal Cannabis Agency (MCA) issues licences for cultivation, manufacture, and supply. Medsafe approves finished products and monitors quality. The NZ Formulary lists products that meet the scheme’s standards, and prescribers use it as the official reference. The New Zealand Ministry of Health publishes the scheme’s operational rules, including the requirement that all products meet Good Manufacturing Practice (GMP) standards and be approved by the Ministry of Health.

A common misunderstanding is that “legal medicinal cannabis” means a patient can legally smoke raw plant material or buy unregulated products. Under New Zealand’s Medicinal Cannabis Scheme, the legal product is a manufactured pharmaceutical, and the raw flower, while available, is prescribed and dispensed through a pharmacy, not a dispensary. The Misuse of Drugs Act governs this pathway. Prescriptions are issued by medical practitioners, and products must meet GMP standards and be approved by the Ministry of Health. This page explains the difference between CBD and THC, how they are regulated in New Zealand, and how to compare products on the prescription pathway.

KEYWORD: CBD and THC explained

CBD and THC explained

The one thing to understand first

CBD and THC are the two cannabinoids you will see on every New Zealand medicinal cannabis label. They are not interchangeable, and the ratio between them often matters more than the total amount. THC is the molecule that produces the “high”; CBD does not. Under New Zealand’s Medicinal Cannabis Scheme, both are prescription medicines, not over-the-counter products, and the legal route is through a medical practitioner and a pharmacy. The most common mistake is assuming “legal medicinal cannabis” means you can smoke raw plant material or buy unregulated products. The legal product is a manufactured pharmaceutical, dispensed through a pharmacy, not a dispensary.

The core difference

Attribute THC (delta-9-tetrahydrocannabinol) CBD (cannabidiol)
Main effect Psychoactive; produces the “high” Non-psychoactive; no euphoric high
Primary uses Pain, muscle spasticity, appetite stimulation, nausea Anxiety, inflammation, seizure disorders, chronic pain
Onset (inhaled) 5-10 minutes 5-10 minutes
Onset (oral oil) 30-90 minutes 30-90 minutes
Duration (inhaled) 2-4 hours 2-4 hours
Duration (oral oil) 6-8 hours 6-8 hours
Common side effects Drowsiness, dry mouth, increased appetite, dizziness Generally well tolerated; can cause fatigue, diarrhoea, or changes in appetite at high doses
Psychoactive Yes No (at typical doses)
Legal pathway in NZ Prescription under Misuse of Drugs Act Prescription under Misuse of Drugs Act (CBD is not controlled, but as a medicine it is prescription-only)

THC (delta-9-tetrahydrocannabinol) is the main psychoactive compound in cannabis. In New Zealand’s Medicinal Cannabis Scheme, THC content is measured in mg/g or percent and determines both therapeutic effect and the level of regulatory control. High-THC products are used for pain, muscle spasticity, nausea, and appetite stimulation. THC produces the “high” that many patients find uncomfortable, so the NZ Formulary and clinical guidance recommend starting at a low dose and titrating slowly. Products containing more than 2% THC are controlled drugs under the Misuse of Drugs Act 1975, which is why they require a prescription and cannot be legally possessed without one. Medsafe approval under the Misuse of Drugs (Medicinal Cannabis) Regulations 2019 is required for each product before it can be prescribed. The NZ Formulary lists THC and CBD monographs with dosing guidance for clinicians, but the evidence base for THC’s efficacy is strongest for chronic pain, nausea and vomiting, and appetite stimulation in palliative care; the evidence for other conditions is less certain.

CBD (cannabidiol) is non-psychoactive, so it does not produce a “high”; it is used for anxiety, inflammation, and seizure disorders. In New Zealand, CBD was rescheduled in 2021 so that products containing 98% or more CBD and 2% or less of other cannabinoids are not controlled drugs, but they still require a prescription under the Medicines Act. THC is the psychoactive compound; it is controlled under the Misuse of Drugs Act, and its prescription is more restricted. The ratio of THC to CBD determines the clinical experience. High-THC products are used for pain, muscle spasticity, and appetite stimulation; high-CBD products are used for anxiety, inflammation, and epilepsy. A 1:1 ratio is common for balanced relief. The doctor’s decision is not “THC is good, CBD is better”; it is about matching the patient’s symptom profile and risk tolerance.

The NZ Medicinal Cannabis Scheme (under the Misuse of Drugs (Medicinal Cannabis) Amendment Act 2018, effective 1 April 2020) sets quality standards and licences. Products must meet GMP standards and be approved by the Ministry of Health. The scheme does not legalise smoking raw plant material; the legal pathway is a prescription from a medical practitioner dispensed through a pharmacy. The raw flower, while available, is prescribed and dispensed through a pharmacy, not a dispensary. Under the Misuse of Drugs Act, possession without a prescription remains illegal.