Last updated: October 2026
Yes, CBD can interact with some medicines. It slows liver enzymes, mainly CYP3A4 and CYP2C19, that break down many drugs, which can raise their levels. The same enzyme is behind grapefruit warnings, so a grapefruit warning on your medicine is a useful red flag. Blood thinners, some epilepsy, transplant and heart medicines matter most. Ask a pharmacist before combining.
Below: how interactions work, the grapefruit warning explained, a table of medicine types to check, how dose affects risk, and how to use CBD more safely if you take medication.
How CBD interacts with medicines
Your liver uses a family of enzymes called cytochrome P450 (CYP450) to break down many medicines. CBD is broken down by some of these enzymes and also slows them down. If a medicine relies on the same enzymes, more of it can stay in your blood for longer, which can increase side effects. Less often, other medicines can lower CBD levels; for example, the antibiotic rifampicin cut CBD levels by about 30% in a study for the prescription CBD medicine.
CBD can also add to the effects of medicines that cause drowsiness, such as sedatives, some painkillers and alcohol. See CBD and alcohol.
The grapefruit warning explained
Some medicine leaflets say to avoid grapefruit or grapefruit juice. That’s because grapefruit blocks the enzyme CYP3A4 in the gut, raising levels of certain medicines. CBD affects the same enzyme, so if your medicine carries a grapefruit warning, it’s a sign to check with a pharmacist before using CBD. No grapefruit warning doesn’t guarantee there’s no interaction, because CBD also affects other enzymes such as CYP2C19.
Medicines to check before using CBD
| Medicine type | Examples | Why it matters |
|---|---|---|
| Blood thinners | Warfarin | A case report found CBD raised warfarin levels and bleeding risk |
| Epilepsy medicines | Clobazam, valproate, others | Known interactions with prescription CBD, including liver enzyme rises with valproate |
| Transplant and immune medicines | Tacrolimus, ciclosporin, everolimus | CBD raised everolimus levels about 2.5-fold in a study; small changes can matter |
| Some heart and cholesterol medicines | Some statins, calcium channel blockers, anti-arrhythmics | Many carry grapefruit warnings |
| Sedatives and sleeping tablets | Benzodiazepines such as diazepam, midazolam | Higher levels and added drowsiness |
| Strong painkillers | Some opioids | Added drowsiness; some are broken down by CYP3A4 |
| Antidepressants and anxiety medicines | Some SSRIs, amitriptyline | Levels can change; added drowsiness |
| Medicines with a narrow safe range | Lithium, some thyroid and heart medicines | Small changes in level can cause problems |
This isn’t a complete list. Always check your specific medicine with a pharmacist. See also CBD and antibiotics and CBD before surgery.
Does the amount of CBD matter?
Yes. Most interaction studies used prescription doses of hundreds of mg a day. At supplement amounts, around 10mg a day, effects are likely to be much smaller, but they haven’t been well studied, so caution still applies for higher-risk medicines. Topical CBD such as a balm reaches the bloodstream in much smaller amounts.
The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.
How to use CBD more safely
- Ask your pharmacist with your medicine list in hand. It’s free and quick.
- Start low and increase slowly.
- Separate doses where advised, for example taking CBD a few hours apart from a medicine.
- Keep the amount steady once you’ve settled on it, as big changes are more likely to shift medicine levels.
- Tell your GP if you’re having regular blood tests for a medicine, such as an INR test for warfarin.
- Choose THC-free, lab-tested CBD, so you know what you’re taking.
Signs of an interaction
Stop CBD and contact your GP or pharmacist if you notice unusual drowsiness, dizziness, unexpected bruising or bleeding, stronger side effects from your usual medicine, or yellowing of the skin or eyes. Call 999 for severe symptoms such as heavy bleeding, chest pain or difficulty breathing.
FAQs
Can CBD interact with medications?
Yes. It slows liver enzymes that break down many medicines, which can raise their levels. Ask a pharmacist before combining CBD with any regular medicine.
What does the grapefruit warning mean for CBD?
Grapefruit and CBD both affect the enzyme CYP3A4. If your medicine has a grapefruit warning, check with a pharmacist before using CBD.
Which drugs should not be taken with CBD?
Take particular care with blood thinners, some epilepsy, transplant, heart and sedative medicines. Always check your specific medicine with a pharmacist.
Can I take CBD with antidepressants?
Speak to your GP or pharmacist first. CBD can change levels of some antidepressants and add to drowsiness.
Does CBD balm interact with medication?
Much less CBD reaches the bloodstream from skin products, so interactions are less likely, but check with a pharmacist if you take high-risk medicines.
How long should I leave between CBD and my medication?
Ask your pharmacist; for some medicines, a gap of a few hours may help, but it doesn’t remove the risk for all of them.
Sources
- Balachandran P et al. Cannabidiol interactions with medications, illicit substances, and alcohol: a comprehensive review. J Gen Intern Med, 2021.
- emc. Epidyolex: summary of product characteristics (section 4.5, interactions).
- Bailey DG et al. Grapefruit-medication interactions: forbidden fruit or avoidable consequences? CMAJ, 2013.
- Grayson L et al. An interaction between warfarin and cannabidiol: a case report. Epilepsy Behav Case Rep, 2018.
- GOV.UK. FSA consumer advice on CBD.
