CBD drug interactions: which medicines to be careful with

Yes, CBD can interact with some medicines. CBD slows down several liver enzymes that also break down many common drugs, so levels of those drugs can rise. The best-documented cases involve warfarin, clobazam, valproate and tacrolimus. If you take any regular medicine, talk to your doctor or pharmacist before using CBD.

Can CBD interact with my medication?

Yes, it can. Whether it matters for you depends on which medicine you take, how much CBD you use and how narrow the safe range of your medicine is. For most people the question is not "is it dangerous?" but "does my doctor need to check a level or adjust a dose?".

The most detailed information comes from Epidyolex, the prescription CBD medicine approved in the EU for certain rare forms of epilepsy. Its official product information lists several confirmed interactions and advises doctors to monitor patients closely (EMA). A 2024 systematic review found 31 published reports in which cannabinoids changed the levels of, or caused side effects with, medicines that have a narrow safety margin. Warfarin, valproate, tacrolimus and sirolimus were reported most often (Nachnani 2024).

How does CBD affect the way my body handles medicines?

Your liver and gut use a family of enzymes called cytochrome P450 (CYP for short) to break medicines down so your body can clear them. Think of these enzymes as workers at a checkout. CBD uses the same checkout. While CBD is there, the workers handle other medicines more slowly, so those medicines can build up in the blood.

A higher level can mean stronger effects or more side effects. The reverse can also happen: some medicines speed up these enzymes and lower the level of CBD instead.

CBD affects several of these enzymes (CYP3A4, CYP2C19, CYP2C9, CYP2C8 and CYP1A2), plus other clearing enzymes and a "pump" in the gut wall that pushes some drugs back out (EMA; Brown & Winterstein 2019). Not every enzyme is affected equally. In a study for the medicine's approval, CBD did not change the level of midazolam, a standard test drug for the main liver enzyme. But it raised everolimus about 2.5-fold, probably by blocking the gut pump (EMA). That is why the evidence has to be looked at drug by drug.

Which medicines need the most caution with CBD?

The table sums up what is known for the main drug groups. The High, Medium and Low caution labels are our plain-language summary of the cited sources, not an official grading. The evidence in brackets is strong (controlled studies in people or the official medicine label), moderate (case reports or small patient studies) or limited (lab data or theory only).

This table is not complete. Researchers at Penn State have listed 57 prescription medicines with a narrow safety margin that could be affected by cannabinoids (Kocis & Vrana 2020), and they run a free online interaction checker (CANN-DIR). A medicine that isn't in the table is not automatically fine.

Is it safe to take CBD with blood thinners like warfarin?

Don't combine them without your doctor's knowledge. Warfarin has a narrow margin: a small rise in its effect can raise the risk of bleeding. In two published cases, adults starting prescription CBD needed their warfarin dose lowered by about 20% and 30% to keep their INR in range (Grayson 2018; Cortopassi 2020). Both reports recommend checking INR more often when CBD is started. If you already use CBD and are prescribed warfarin, tell the clinic that manages your INR.

Can I take CBD with antidepressants (SSRIs)?

It depends on the medicine. In a 2026 study run by the US Food and Drug Administration, 20 healthy adults took 2.5 mg of CBD per kg of body weight twice a day. Their exposure to citalopram rose by 43% (Salcedo 2026). Lab work suggests escitalopram behaves the same way, while sertraline, fluoxetine and mirtazapine were hardly affected (Anderson 2021). Don't stop or change an antidepressant on your own. Ask your prescriber whether CBD fits with it.

What is the "grapefruit warning", and does it apply to CBD?

Grapefruit blocks one of these enzymes (CYP3A4) in the small intestine. With certain medicines, more of the drug then enters the blood and stays in the body longer (US FDA). That is why the leaflets of some medicines, such as simvastatin, tell you to avoid grapefruit juice (NHS).

CBD affects some of the same enzymes, so a grapefruit warning is a useful signal to ask. It is a rule of thumb, not a test:

• It can over-warn. CBD and grapefruit don't act in exactly the same way. CBD did not change midazolam, a classic grapefruit-sensitive test drug, in the approval studies (EMA).
• It can under-warn. Clobazam and warfarin are mainly handled by other enzymes and may carry no grapefruit warning, yet they are among the best-documented CBD interactions.

So: a grapefruit warning on the leaflet means ask before using CBD. No grapefruit warning? Still ask if you take any regular medicine.

Does the amount of CBD matter?

Yes. Most interaction data come from medicinal doses. Epidyolex is dosed at 5 to 20 mg per kg of body weight a day, which is 350 to 1,400 mg a day for a 70 kg adult (EMA). The tacrolimus case involved 2,000–2,900 mg a day (Leino 2019).

Consumer products are usually far lower. Our classic 10 ml oils hold 1.2 to 12 mg of CBD per drop depending on strength, and they are cosmetics for use on the skin. Our CBD oil dosage guide has the figures for every oil.

A lower dose doesn't mean you can ignore the question. In a 2026 study, a single 30 mg dose of CBD raised amitriptyline levels by 13% in healthy volunteers. The authors expect the effect to be larger with daily use (Gorbenko 2026). How much a small rise matters depends on your medicine. For warfarin or tacrolimus even a modest change can matter.

Food regulators draw the same line. EFSA concluded that the safety of CBD for people taking other medicines "cannot be established" (EFSA Journal 2026), and the UK FSA does not recommend CBD for people taking any medication, unless under medical direction (FSA guidance). Their daily limits for healthy adults are explained in what the regulators say about CBD.

Does it matter if I use CBD on the skin rather than by mouth?

The interaction studies above all used CBD taken by mouth, at doses far above typical cosmetic use. We found no interaction studies for CBD applied to the skin, so include it when you list your products for your doctor. Our oils are notified as cosmetics for use on the skin.

How do I talk to my doctor or pharmacist about CBD?

Doctors can only check what they know about. In the 2024 review, 18 of the 31 reports (58%) came to light because clinicians found an unexpected level of a prescribed medicine (Nachnani 2024). Telling them early avoids that.

When should I stop and get help?

Extra drowsiness is the main concern when CBD is combined with sleeping pills or sedatives; our guide to CBD oil and sleep covers it. For everyday side effects, see CBD side effects.

Pets on medication need their own advice: ask your vet first, and see our guides to CBD for dogs and CBD for cats.

Every batch of our oils has a published lab report showing its CBD and THC content. Find the lab report for your bottle to show your doctor or pharmacist.