Medical cannabis is legally prescribed in the UK for a range of eligible conditions when conventional treatments have not provided sufficient relief. For many patients, it forms part of a carefully managed, specialist-led treatment plan.
Like all prescribed medicines, medical cannabis side effects are possible. These effects vary widely between individuals and depend on factors such as the type of product prescribed, cannabinoid content, dose, method of administration, and a person’s overall health.
This page provides clear, balanced, and UK-compliant information about medicinal cannabis side effects, and how clinicians work with patients to manage them safely.
Important: Eligibility and suitability for medical cannabis are always assessed on a case-by-case basis by a Medicann clinician.
Medical cannabis refers to cannabis-based products for medicinal use (CBPMs) prescribed by a specialist doctor. These products may contain:
The side effects a patient may experience largely depend on the specific cannabinoids present, their ratios, how the medicine is taken, and the individual’s endocannabinoid system.
Not everyone experiences side effects. Many patients report none or only mild effects that settle as the body adjusts. However, understanding potential risks is an important part of informed consent and safe prescribing.
Some cannabis side effects can occur with both CBD- and THC-containing medicines, particularly during the early stages of treatment or following dose changes.
General cannabis side effects may include:
These effects are usually temporary and often improve as dosing is adjusted or tolerance develops.
CBD is non-intoxicating and does not cause a “high”. As a result, CBD side effects are generally considered mild compared to THC.
Patients prescribed CBD-dominant products may experience:
CBD oil side effects are more likely to occur at higher doses or when starting treatment. Clinicians often begin with a low dose and increase gradually to minimise unwanted effects.
In rarer cases, some patients report:
CBD can also interact with certain medications by affecting how they are metabolised in the liver. This is why a full medication review is always carried out before prescribing.
THC is the psychoactive cannabinoid in medical cannabis. While it may be appropriate for some patients, THC side effects require closer monitoring.
These can include:
Because of these effects, patients prescribed THC-containing medicines are advised not to drive unless they meet legal driving requirements and feel unimpaired.
Some people may experience:
These effects are more likely at higher doses or in patients who are sensitive to THC. For this reason, clinicians may recommend CBD-dominant products first, particularly for patients new to medical cannabis.
Oils are one of the most commonly prescribed formats. Side effects may develop gradually due to slower absorption.
Possible effects include:
Oils allow for precise dosing, which helps clinicians manage side effects effectively.
Inhaled products act more quickly, meaning side effects can appear sooner.
These may include:
Your clinician will explain appropriate use and dosing to reduce risk.
These formats can cause:
They may be suitable for those who prefer not to inhale medication.
While uncommon, some medical cannabis side effects require prompt clinical review.
These may include:
Patients are encouraged to report any concerning effects to their Medicann clinician as soon as possible.
Side effects can be influenced by:
This is why medical cannabis is only prescribed following a comprehensive specialist assessment.
Managing medical cannabis side effects is a key part of safe, ongoing care. Medicann clinicians use several strategies to reduce unwanted effects.
Most patients begin on a low dose, which is increased gradually. This approach allows the body to adjust and helps identify the lowest effective dose.
If side effects occur, clinicians may:
Certain formulas, such as those that are an indica strain, may cause drowsiness. Taking doses in the evening may help reduce daytime drowsiness. Spacing doses can also minimise side effects.
Regular follow-ups allow clinicians to assess benefits and side effects, ensuring treatment remains appropriate and safe.
Medical cannabis may interact with certain medications, including some antidepressants, pain medicines, and antiepileptic drugs. This is why it is essential to disclose all current medications during your assessment.
Medical cannabis should never be combined with illicit cannabis or altered without medical guidance.
In most cases, side effects are temporary and resolve with dose adjustments or over time.
CBD is generally better tolerated and non-intoxicating, but all medicines can cause side effects in some individuals.
Not always, but careful prescribing and monitoring significantly reduce risk.
Contact your Medicann clinician. Do not change or stop your medication without medical advice.
Understanding the pros and cons and side effects of cannabis helps patients make informed decisions about their care. If you’re considering medical cannabis and want to understand whether it may be suitable for you, check your eligibility or contact our team today. You can also learn more on our FAQ page.
Medicann is the lowest-cost medical cannabis clinic in the UK, offering free consultations for life, no repeat prescription fees, and same-day UK dispatch. Our specialist clinicians are here to guide you through every step, safely and transparently.
