Reading labels and certificates

How to read a New Zealand medicinal cannabis label

Every legal medicinal cannabis product in New Zealand carries two things you need to be able to read: the label on the container and the certificate of analysis (CoA) that accompanies the batch. The method below helps you interpret both, so you can compare options and understand what a prescription actually delivers. It does not rank brands or recommend doses.

What the label must show

Under the Medicinal Cannabis Scheme, dispensed products are manufactured pharmaceuticals, not herbal remedies. The label must show the active cannabinoids in milligrams per gram (mg/g) or as a percentage.

THC (delta-9-tetrahydrocannabinol) is the main psychoactive compound. CBD (cannabidiol) is the non-psychoactive compound. Labels list both as either mg/g or as a percentage. A product labelled “THC 25” means 25 mg of THC per gram. A 10:10 preparation means 10 mg/g THC and 10 mg/g CBD. The ratio, not the absolute number, usually determines the clinical effect. A 1:1 option is commonly used for balanced pain relief, while a high-THC option (e.g., 25:1) is used for breakthrough pain or sleep, and a high-CBD option (e.g., 1:20) is used for anxiety or inflammation without intoxication. This is not a recommendation; it describes how labels are read.

Medsafe approves these products under the Medicinal Cannabis Scheme. The scheme requires preparations to meet GMP (Good Manufacturing Practice) standards and gain Ministry of Health approval before prescribing. Check the official list of notified products on the Medsafe website.

The four mandatory label items

Every dispensed label must show:

1. The active cannabinoid amounts, written as THC and CBD in mg/g or as a percentage (e.g., “THC 25 mg/g” or “10:10”).
2. The batch number, a unique code for that production run.
3. The expiry date. Medicinal cannabis degrades, especially oils.
4. The product name and form, e.g., “Medleaf THC25 Flower” or “Tilray 10:10 Oil”.

How to read the numbers

Cannabinoid amounts are listed in milligrams per gram (mg/g) or as a percentage (%). They are not interchangeable at face value: 10 mg/g means 1% by weight, so a 10:10 preparation has 10 mg/g THC and 10 mg/g CBD.

The two numbers on a label (e.g., “10:10” or “25:1”) are the THC:CBD ratio. The ratio tells you the balance of psychoactive to non-psychoactive cannabinoids, but it does not tell you the total amount in the container. For example, a 10:10 oil in a 30 mL bottle contains 300 mg of THC and 300 mg of CBD, while a 10:10 flower is 1% THC and 1% CBD by weight.

Driving and impairment warning

Do not drive or operate machinery after taking THC-containing preparations until you know how they affect you. THC impairs coordination, reaction time and judgement. Discuss driving safety with your prescriber. In New Zealand, driving while impaired by any drug is an offence under the Land Transport Act 1998.

Read a label in five steps

1. Find the THC and CBD amounts per gram or per millilitre (mg/g or mg/mL). This is the concentration, not the total dose.
2. Check the THC:CBD ratio. A 1:1 preparation (e.g., Tilray 10:10) means equal parts; a 25:1 is THC-dominant; a 1:20 is CBD-dominant.
3. Note the form (flower, oil, capsule) and the administration route. Flower is inhaled and acts in 5-10 minutes; oils are taken orally and act in 30-90 minutes.
4. Check the batch number and expiry date. These confirm the product is a specific manufactured lot and has not expired.
5. Verify the product is listed under the Medicinal Cannabis Scheme. If it does not appear in the NZ Formulary or lacks Ministry of Health approval, it is not a legal prescription item.

The batch number and certificate of analysis

Batch numbers and expiry dates are essential. Every legal product has both. The batch number ties the product to a Certificate of Analysis (CoA), a quality document issued by an independent lab. The CoA shows the actual measured cannabinoid content, terpene profile, and contaminant testing (pesticides, heavy metals, microbials). If a label says “THC 25 mg/g” but the CoA for that batch says 22 mg/g, the CoA is the ground truth; labels can round or drift.

In New Zealand, the Medicinal Cannabis Scheme requires every product to be tested and the results kept for inspection. If you are a patient, ask your pharmacist for the CoA for your specific batch. If you are a clinician, check the batch certificate before you prescribe. The batch number on the label is the key to traceability: it links the product you hold to the specific quality tests done on that batch, not to a generic description.

Full label checklist

Use this checklist each time you receive a dispensed product.

Verify the basics

1. Find the batch number and expiry date. Every legal product has both. If either is missing, the item is not part of NZ’s Medicinal Cannabis Scheme.
2. Identify the form (flower, oil, capsule, powder). This determines onset and duration.
3. Confirm the product has a Medsafe approval number (e.g., “NZ” prefix) or is listed in the NZ Formulary. This is the only legal pathway.
4. Verify the product is on the NZ Medicinal Cannabis Scheme’s list; if it is not listed, it is not legally dispensable in New Zealand.

Check the cannabinoid profile

1. Check the active cannabinoids, usually listed as mg/g or %. For flower, THC and CBD are listed as percentages (e.g., “THC 22%”). For oils, they are listed as mg/mL (e.g., “THC 25 mg/mL”).
2. Look for the THC:CBD ratio. This is the single most useful number for predicting the experience. A 1:1 ratio is balanced; high-THC (e.g., 20:1) is more psychoactive; high-CBD (e.g., 1:20) is less psychoactive.
3. Compare the THC:CBD ratio, not just total THC, because the ratio determines the experience more than the absolute amount.
4. Be wary of preparations that list only “CBD” or “THC” without a ratio; a 10:10 contains equal amounts, a 20:5 has four times more THC than CBD; the ratio determines the experience more than the absolute numbers.

Confirm the batch quality

1. Note the batch number and expiry date. Products are batch-tested; the label’s numbers apply only to that batch.
2. Check the certificate of analysis (CoA). It should show actual measured cannabinoid content, not just label claims, plus tests for pesticides, heavy metals, mould, and residual solvents.
3. Ask the pharmacist for the certificate of analysis (CoA) for the specific batch; the CoA shows actual cannabinoid content, terpenes, and contaminant testing, not just the label claim.

Calculate your totals

1. For oils, check the concentration per mL (e.g., 25 mg/mL THC) and the total volume (e.g., 30 mL), then calculate total mg per bottle.
2. For flower, check the percentage of THC and CBD, and the batch number; potency varies between batches, so the label is a snapshot, not a promise.
3. Check the expiry date and batch number; products degrade over time, and the batch number lets you verify the certificate of analysis.

Handle and store safely

1. Store correctly: oils degrade with heat and light; flower degrades over time. Check the expiry date and discard expired products. This is a safety issue, not a preference.
2. Do not mix with alcohol or other sedatives without discussing it with your prescriber first.

Sources

• NZ Medicinal Cannabis Agency (MCA), Official scheme documents (2023)
• New Zealand Ministry of Health, Medicinal Cannabis Guidance (2023)
• Medsafe, Product approval and quality standards (2023)
• NZ Formulary, Cannabis monograph (2023)
• Healthify, Medicinal cannabis patient information (2023)
• New Zealand Medical Journal (NZMJ), systematic review on medicinal cannabis (2023)