What drugs should not be taken with CBD?

Key Takeaways:

• CBD may interact with some prescription medication, such as blood thinners, anti-seizure medication, immunosuppressants and benzodiazepines
• Certain over-the-counter medicines and herbal remedies, including kava and St John’s Wort, can also lead to CBD drug interactions
• CBD is metabolised in the liver using cytochrome P450 liver enzymes, and so are certain medications: if they’re taken together, they may compete for these enzymes, potentially leading to too much or too little of your medication in your system
• Always check with your healthcare provider if you're taking medications and wish to take CBD, particularly those medications that carry a ‘grapefruit warning’

In the UK, CBD products are legal and are sold as food supplements, regulated by the Food Standards Agency (FSA) under novel food rules.

Epidyolex and Sativex are CBD-based medicines, licensed with the Medicines and Healthcare Products Regulatory Agency (MHRA) to manage seizures associated with some forms of epilepsy and muscle spasms associated with multiple sclerosis, respectively. Aside from licensed medicines such as Epidyolex and Sativex, CBD products cannot make any explicit medical claims.

CBD doesn’t cause a high, but due to the way it’s processed by the body, it can interact with certain medications. Therefore, if you’re taking a prescribed medicine, for any reason, check to see what drugs should not be taken with CBD if you’d like to start taking it.

This article takes an in-depth look at CBD drug interactions, taking CBD safely and why the ‘grapefruit warning’ should be taken seriously.

Can you take CBD if you’re on medication?

Some over-the-counter and prescription medication can interact with CBD. If you’re in any doubt, always check with your GP, pharmacist or specialist healthcare provider.

Why CBD interacts with other medicines

CBD is extracted from the hemp plant, a strain of the Cannabis sativa plant bred to contain very low levels of THC (tetrahydrocannabinol). THC is the compound responsible for the high of using cannabis products. CBD doesn’t cause a high, but it’s still considered an active compound and, as such, can interact with some prescription medication, over-the-counter medicines and herbal remedies that you may be taking.

This is because CBD is metabolised in the liver via cytochrome P450 enzymes (such as CYP2C19 and CYP3A4), which the liver also uses to metabolise certain drugs.

The cytochrome P450 enzyme system

The cytochrome P450 enzyme system is predominantly found in the liver. These liver enzymes are responsible for metabolising, or breaking down, medications, toxins, internal waste and chemical by-products naturally produced by the body.

CBD is also metabolised by the P450 enzyme system, and if you're taking CBD and another medication, they’ll begin to compete for these liver enzymes. The result of this is unpredictable: it may cause the concentration of some medications to reduce and others to increase, a phenomenon known as altered concentration.

When CBD reduces how well a medicine works

Some medicines need to be broken down by liver enzymes before they start working, such as the blood thinner clopidogrel and the painkiller codeine. If CBD blocks these enzymes, less of the active form is produced, so the medicine may not work as well. Depending on why you're taking it, this could be dangerous.

When CBD causes a medicine to build up

CBD can block P450 enzymes, which means some medicines are broken down more slowly and aren't cleared from your system as quickly as they should be. This can cause them to build up to higher levels than intended, increasing the risk of side effects and, in some cases, toxicity.

Overlapping side effects

Some people experience mild side effects from CBD, including drowsiness. Taking CBD with another medication that causes drowsiness can lead to excessive sleepiness and even a mild sedative effect, which can increase your risk of vulnerabilities and accidents.

The grapefruit warning explained

Some prescription medications, such as some blood thinners, blood pressure medication and statins used to manage cholesterol levels, come with a ‘grapefruit warning’. This means that you should avoid consuming grapefruit if you're taking these medications because grapefruit contains compounds that belong to a group of chemicals called furanocoumarins.

Furanocoumarins interfere with the way certain cytochrome P450 enzymes function. If a medication you’re taking is metabolised by these same enzymes, consuming grapefruit could cause its metabolism to be impaired, and for it to build up in the blood, leading to side effects and potential toxicity.

CBD can have a similar effect to furanocoumarins, and as such, CBD should be avoided if you take any medication that carries a grapefruit warning. The Patient Information Leaflet (PIL) that comes with your medication will let you know if it applies.

The grapefruit warning isn’t flawless and cannot be relied upon completely. Instead, it serves as a reminder to check with your healthcare provider before taking CBD if you’re taking any medications.

What drugs should not be taken with CBD?

The following is a list of common prescription medications that may lead to CBD drug interactions, because they may cause excessive drowsiness, put stress on the liver, lead to altered concentrations or cause other side effects.

If you’re taking any of these, or any other medication that you’re concerned about, avoid taking CBD and speak to your doctor.

It’s not an exhaustive list, and you should always check with your doctor before taking CBD if you’re taking medication. You should never stop, reduce or space out your medications to take CBD. If you’ve been told by a healthcare professional that CBD interacts with a drug you’re taking, or it comes with a grapefruit warning, you should avoid CBD altogether.

Herbal remedies and supplements that may interact with CBD

Some herbal remedies may also interact with CBD, including those that can cause drowsiness, such as kava, and those processed by the liver, such as St John's Wort. Melatonin, which is prescription-only in the UK, can also add to drowsiness. If you're in doubt, speak to a doctor or pharmacist.

CBD and alcohol

CBD can be taken with alcohol, but it isn’t well studied. Keep in mind that together, they can amplify each other's effects. This may lead to drowsiness and potentially a sedative effect if used in excess, so if you plan to use them together, exercise caution.

Does the type of CBD product change the risk?

How you take CBD can also impact how a CBD drug interaction may affect you:

Oils and sublingual drops

CBD oil is designed to be taken in drops under the tongue. Some CBD is absorbed through the tissue under the tongue, so it can take effect faster than gummies and other edibles that need to be digested first. This may mean that any side effects become noticeable more quickly.

Drinks, gummies and other edibles

CBD drinks, gummies, and other edibles need to enter the digestive system before being metabolised and entering the bloodstream, resulting in a comparatively slower effect. Therefore, they’re less likely to reach a high concentration peak. But with continued use, they may reach a concentration that leads to CBD drug interactions and side effects, and combining CBD with medicines that may interact is still not advised.

Capsules

CBD capsules have a similar effect to CBD gummies as they need to be digested. Like with CBD edibles, combining them with medications that also use the cytochrome P450 enzyme system isn’t recommended.

Vapes

Inhaling CBD is the quickest way to get CBD into your system, with concentrations peaking within just 30 minutes. This means that any side effects can become acute and affect you quickly.

Balms and other topicals

It’s not yet fully understood how much CBD from creams and balms applied to the skin enters the bloodstream. Therefore, the impact of CBD on any medications you’re taking isn’t yet fully known.

Does the dose make a difference?

Taking a higher dose of CBD may lead to increased interactions and side effects. Similarly, taking a high dose of prescribed medication may also lead to the same. Taking a lower dose of either doesn’t guarantee that you won’t experience a CBD drug interaction.

Most evidence on CBD drug interactions comes from studies of prescription CBD at doses far higher than the FSA's 10mg daily guidance. Interactions at lower doses are less well studied, so they can't be ruled out.

Who should avoid CBD altogether?

If you’ve been made aware of any CBD drug interactions by your doctor due to medications that you're taking, you should avoid using CBD. You should also avoid CBD if you’re pregnant, trying to conceive, breastfeeding or under the age of 18.

What UK regulators say about CBD and medication

NHS Specialist Pharmacy Service guidance advises that anyone taking CBD should let their doctor or pharmacist know, as it may interact with medicines processed by the same liver enzymes.

FSA advice on daily intake and vulnerable groups

The World Health Organization describes CBD as generally well tolerated. However, the FSA advises that people taking medication should not consume CBD unless they have consulted a medical professional.

Otherwise, based on advice from the UK’s Committee on Toxicity (COT) and the Advisory Committee on Novel Foods and Processes (ACNFP), the FSA advises that healthy adults take no more than 10mg of CBD a day.

Novel Food status in Great Britain

CBD food products are classed as novel foods because they don't have a significant history of consumption in the UK or EU before May 1997. This means they must go through the FSA's novel food authorisation process and, like all foods, cannot make medical claims. The Advisory Committee on Novel Foods and Processes (ACNFP), an independent scientific committee, advises the FSA on their safety.

In September 2026, the FSA recommended that ministers in England and Wales authorise the first three CBD food products as novel foods. Two of these are CBD isolates and one is synthetic CBD, all at least 98% pure and intended for adults at up to 10mg per day. If approved, they will be the first CBD food authorisations in Great Britain.

CBD itself is not a controlled substance under the Misuse of Drugs Act 1971. However, CBD products can contain trace amounts of controlled cannabinoids such as THC, and must contain no more than 1mg of these per container.

Possible signs of an interaction to look out for

Signs of a possible CBD drug interaction include:

• Excessive drowsiness
• Feeling dizzy or confused
• A return of the symptoms your medication is supposed to be managing
• New side effects such as nausea and vomiting, diarrhoea, changes to your bowel habits, mood or anything else that started when you began taking CBD
• Nose bleeds, bleeding gums and bruising easily if you're taking a blood thinner such as warfarin
• Signs of a liver problem, such as jaundice (yellowing of the skin and the whites of your eyes), dark urine and fatigue

How to talk to your GP or pharmacist about CBD

CBD is legal in the UK, so speaking to a healthcare provider about using CBD won’t cause alarm. If you’re considering taking CBD, and you take other medicines, speak to your GP about why you’d like to take CBD. Have a complete list of all your medications to hand, and ask for a medication review to make sure they’re all still working for you.

Practical safety steps if you take medication

If you take any prescription medication, over-the-counter medicines or herbal supplements, always check the label or with your prescribing doctor for any CBD drug interactions or the grapefruit warning before using CBD.

These might not be clearly detailed or specifically relate to CBD, but that doesn't necessarily mean it's safe to take CBD. The grapefruit rule is a good place to start (but isn't flawless), and if it’s listed, avoid taking CBD. To be absolutely sure you won't experience any altered concentration effects, always check with a medical professional before taking CBD if you’re taking anything else.

If you take CBD as well as medication and you notice any side effects such as excessive drowsiness, confusion or bleeding, seek medical attention.

More information and research

A comprehensive review of the available literature, published in 2021, found possible CBD drug interactions with several common medications, which we’ve listed in this article. The paper provides a comprehensive list of drug interactions and can serve as a useful reference.

Again, it’s not an exhaustive list, and you should always check with your doctor before starting CBD or if you’ve been prescribed a new medication and you’re taking CBD.

FAQs

Can you take CBD with paracetamol?

No significant interactions between paracetamol and CBD have been identified, but both are processed by the liver. Always stick to the recommended dose and avoid combining alcohol and paracetamol to reduce stress on the liver.

Does CBD interact with the contraceptive pill?

CBD may interfere with some forms of the contraceptive pill. Speak to your GP for information on the type of contraceptive pill you’re taking before using CBD.

How long should you leave between taking CBD and your medication?

If you’ve been told to avoid using CBD due to a medication you’re taking, you should avoid it altogether. There’s no safe recommended gap between the two. You shouldn’t ever stop or reduce a medication or work out your own dose adjustment so that you can take CBD.

Can you take CBD before surgery or an anaesthetic?

Tell your surgical team if you take CBD before any procedure or anaesthetic, and follow their advice on whether to stop taking it beforehand and when to restart.

Does CBD affect blood pressure on its own?

A small study found that a single 600mg dose of CBD temporarily lowered blood pressure in healthy men. That dose is far higher than the FSA's 10mg daily guidance. If you take blood pressure medication, speak to your GP before using CBD.

References

Balachandran, P., Elsohly, M. & Hill, K. P. (2021). Cannabidiol interactions with medications, illicit substances, and alcohol: a comprehensive review. Journal of General Internal Medicine, 36, 2074–2084. https://link.springer.com/article/10.1007/s11606-020-06504-8

Brown, J. D. & Winterstein, A. G. (2019). Potential adverse drug events and drug–drug interactions with medical and consumer cannabidiol (CBD) use. Journal of Clinical Medicine, 8(7), 989. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6678684/

Bykov, K. (2021, January 11). CBD and other medications: Proceed with caution. Harvard Health. https://www.health.harvard.edu/blog/cbd-and-other-medications-proceed-with-caution-2021011121743

Chesak, J. (2019, November 15). CBD and drug interactions: What you need to know. Healthline. https://www.healthline.com/health/cbd-and-drug-interactions-what-you-need-to-know

Food Standards Agency. Cannabidiol (CBD) guidance. GOV.UK. https://www.gov.uk/government/publications/cannabidiol-cbd-guidance/cannabidiol-cbd-guidance

Food Standards Agency. (2026, June 22). Food Fact Check: CBD safety and health claims. https://food.blog.gov.uk/2026/06/22/food-fact-check-cbd-safety-and-health-claims/

Food Standards Agency. (2026). CBD novel food applications: recommendations to ministers on first authorisations. GOV.UK. https://www.gov.uk/government/publications/food-standards-agency-september-2026-board-meeting/cbd-novel-food-applications-recommendations-to-ministers-on-first-authorisations

Food Standards Agency. Novel foods authorisation guidance. https://www.food.gov.uk/business-guidance/regulated-products/novel-foods-guidance

Home Office. (2024). Cannabis, CBD and other cannabinoids: drug licensing factsheet. GOV.UK. https://www.gov.uk/government/publications/cannabis-cbd-and-other-cannabinoids-drug-licensing-factsheet

Jadoon, K. A., Tan, G. D. & O’Sullivan, S. E. (2017). A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study. JCI Insight, 2(12), e93760. https://insight.jci.org/articles/view/93760

Millar, S. A., Stone, N. L., Yates, A. S. & O’Sullivan, S. E. (2018). A systematic review on the pharmacokinetics of cannabidiol in humans. Frontiers in Pharmacology, 9, 1365. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6275223/

Thorpe, M. (2026, July 1). Should I avoid grapefruit with my medication? Healthline. https://www.healthline.com/nutrition/grapefruit-and-medications

World Health Organization Expert Committee on Drug Dependence. (2018). Cannabidiol (CBD) critical review report. https://cdn.who.int/media/docs/default-source/controlled-substances/whocbdreportmay2018-2.pdf

This article is for informational purposes only and does not constitute legal or medical advice. Please consult your healthcare provider before starting any new supplement, especially if you are pregnant, breastfeeding or taking other medications.

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