A prescription change can alter more than the name on the package. The form, labelled cannabinoid content, instructions, manufacturer or batch may be different too. A practical comparison starts with the old and new pharmacy labels, followed by the facts your prescribing team wants you to report.
Treat two products with similar names, THC figures or CBD figures as different unless the prescribing team confirms otherwise. Many cannabis-based medicinal products are unlicensed medicines. GMC guidance says doctors must support informed decisions and provide enough information for treatment to be managed safely. Get the reason for the change and any unclear instructions confirmed before first use.
Start with the two pharmacy labels
Put the old and new packages side by side. Cover your personal details if you make a photo or note. Copy what each dispensing label says rather than relying on a product name from memory.
Record:
- the full product name;
- the form, such as oil, capsule or dried flower for vaporisation;
- the labelled THC and CBD content or strength, including the units;
- the written directions on the dispensing label;
- the quantity supplied;
- the manufacturer or supplier if shown;
- the batch number and expiry date;
- the date you started the new supply.
Copy the units exactly as they appear. A number without its unit can leave the prescribing team with an incomplete record of what was supplied.
How to read a medical cannabis prescription label covers the usual label fields in more detail.
Separate the product facts from your response
There are two useful columns in this comparison: what changed on paper, and what you noticed after the prescribed change.
The product facts come from the label, packaging and information supplied with the medicine. Your response is a factual account of symptoms, side effects and practical effects. Keeping those columns separate gives the clinic clearer information without turning a personal note into a treatment decision.
For the response column, note:
- the symptom or treatment goal being reviewed;
- any new or changed side effect;
- sleepiness, dizziness, nausea, mood change, feeling high or another effect that affected normal activity;
- whether work, driving, caring, cooking or another safety-sensitive task was affected;
- other medicines that may be relevant;
- the date and time of anything you want the clinic to review.
NHS guidance lists dizziness, tiredness, mood or behaviour change, feeling high and hallucinations among possible side effects. It also says CBD and THC can affect how other medicines work. Report side effects to your medical team and include a complete medicines list when the clinic reviews the change.
What the THC and CBD figures can tell you
The labelled THC and CBD content helps identify what was supplied. It does not predict the exact effect for an individual patient, and a similar headline ratio does not prove that two products are clinically interchangeable.
A THC-to-CBD ratio is only one part of the record. The form, concentration, written directions and individual response still matter. Keep the original units in your note so the prescribing team can interpret them correctly.
For more background, read THC and CBD ratios explained. Use the figures to ask a clearer question while leaving prescription changes to the prescribing team.
Form and instructions need their own check
A change of form can bring different practical instructions as well as a different product. Follow the current dispensing label and the information supplied by the prescribing team or pharmacy.
Follow the current instructions for the new form, concentration or product. Any disagreement between the package, dispensing label and clinic instructions needs clarification before first use.
Useful questions include:
- What was the reason for this prescription change?
- Which details on the new label are different from the previous one?
- Are the written instructions unchanged?
- What effects or side effects does the clinic want me to record?
- Who should I contact if the supplied product or label does not match what I expected?
- When will the change be reviewed?
Keep dose, timing, route and changing back out of the comparison note. Those are prescription decisions; the note simply gives the prescribing team better information.
Copy the batch details without interpreting them
Copy the batch number and expiry date if they appear on the package. Keep them beside the product name and start date so everyone reviewing the change can see which package the note describes.
If the supplied item or label does not match what you expected, keep the package and raise that specific discrepancy with the dispensing pharmacy. The batch record is a reference point, not a verdict on the medicine.
Batch numbers and certificates of analysis in medical cannabis explains what those records can and cannot establish.
When the change needs quicker advice
A label you cannot understand, an item that appears different from the prescription or a new side effect needs prompt attention. NHS guidance says side effects from medical cannabis should be reported to the medical team; suspected adverse reactions can also be reported through the MHRA Yellow Card scheme.
Use NHS 111 when you need medical help now and are unsure what to do. Call 999 or go to A&E when someone is seriously ill, their life is at risk or they are in immediate danger.
Do not drive or carry out safety-sensitive tasks while impaired. GOV.UK says it is illegal to drive when legal or illegal drugs make you unfit to do so. Ask a doctor, pharmacist or healthcare professional if you are unsure about driving with a prescribed medicine.
A useful comparison note
Keep the note short enough to use at a review:
- Previous product: copy the name, form, labelled THC/CBD details and instructions.
- New product: copy the same fields, plus the batch number and start date.
- Reason for change: record the clinic’s explanation in plain words.
- What happened: list the symptoms, side effects and practical effects you noticed.
- Questions: write down anything unclear about the label, supply or review plan.
That record is useful precisely because it does not decide which product is better. It gives the prescriber and pharmacy a clear account of what changed and what needs checking.
Read next
- How to read a medical cannabis prescription label
- THC and CBD ratios explained
- Batch numbers and certificates of analysis in medical cannabis
- What to record in a medical cannabis side-effect diary
