Why this matters
If you have started prescribed medical cannabis, you may notice side effects. It is important to know what to report to your clinic or pharmacist and when to seek urgent help.
Research into medical cannabis side effects is still developing. The NHS notes that common side effects can include a dry mouth, feeling sleepy, and changes in appetite. NICE guideline NG144 also highlights that side effects should be monitored and reported to the prescriber. This guide is here to help you understand what you might experience, and how to talk about it at your next review.
What are the most common side effects?
Dry mouth (xerostomia) A dry or sticky feeling in the mouth can occur. If it persists or makes eating or speaking difficult, mention it to your clinic or pharmacist.
Appetite changes Some people notice a change in appetite. If this affects your weight or nutrition, tell your clinician.
Drowsiness or sedation Feeling sleepy or less alert can occur. Do not drive or operate machinery if you feel drowsy. If it feels excessive or worrying, tell your clinic.
Other possible side effects Other effects can include dizziness, headache, nausea or confusion. Report anything worrying to your medical team.
How to manage mild side effects at home
For mild effects, follow the product information and your prescriber’s plan. If you need practical advice about dry mouth, appetite or drowsiness, ask your pharmacist or clinician rather than changing how you use your medicine yourself.
You might find it useful to keep a simple side effect diary. This can help you spot patterns and give your clinician clear information at your review. Our guide on what to record in a side effect diary has more detail.
What to ask your clinic or pharmacy
- “Is this side effect something I should expect, or does it need attention?”
- “Is there anything I should discuss with the pharmacist or prescriber about this side effect?”
- “How long should I wait before reporting a side effect that does not go away?”
- “What should I do if this side effect is affecting daily life?”
- “Can you recommend a saliva substitute or other product for dry mouth?”
What this guide cannot decide for you
This guide is for information only. It does not replace advice from your prescriber, pharmacist, or clinician. Do not ask your clinic about your treatment plan, route, product, or timing without speaking to them first. If you experience a severe or worrying side effect, contact your clinic or NHS 111. In an emergency, call 999.
Read next
- Medical cannabis side effects: a broader overview
- What to record in a medical cannabis side effect diary
- Start low and go slow: a guide to finding your dose
Sources
- NHS: Medical cannabis – https://www.nhs.uk/medicines/medical-cannabis/
- NICE guideline NG144 – https://www.nice.org.uk/guidance/ng144
- NHS England: Cannabis-based products for medicinal use – https://www.england.nhs.uk/long-read/cannabis-based-products-for-medicinal-use-cbpms/
- GMC: Information for doctors on cannabis-based products for medicinal use – https://www.gmc-uk.org/professional-standards/learning-materials/information-for-doctors-on-cannabis-based-products-for-medicinal-use
- CQC: Cannabis-based medicinal products – what CQC expects from providers – https://www.cqc.org.uk/guidance-providers/healthcare/cannabis-based-medicinal-products-what-cqc-expects-providers
