CBD can change how your body processes some medicines. For a few of them, this has been measured in human studies and can matter for your health. For many others, an interaction is possible in theory but has never been tested.

This article explains how CBD interacts with medicines, what the research actually shows, and which common medicines need the most caution. It includes a table of frequently used medicines and what is known about each one in combination with CBD.

The short answer

CBD slows down several liver enzymes that break down medicines, mainly CYP2C19 and, to a lesser extent, CYP2C9, CYP3A4 and CYP1A2. This can raise the levels of some medicines in your blood.
Human studies have confirmed clinically relevant interactions with citalopram, clobazam, tacrolimus, everolimus and caffeine, and case reports describe interactions with warfarin.
Most interactions were measured at high doses of CBD, of 300 mg per day or more. At lower doses, the risk is less studied, which is not the same as proven safe.
In 2026, EFSA concluded that the safety of CBD for people taking medication cannot be established.
If you take any prescription medicine, talk to your doctor or pharmacist before using CBD, and never change or stop your medicine on your own.

How CBD affects other medicines

Most medicines are broken down in the liver by a family of enzymes called cytochrome P450 (CYP). When a substance slows down one of these enzymes, medicines that depend on it are cleared more slowly and stay in the blood at higher levels. Depending on the medicine, this can strengthen its effect or its side effects.

CBD is mainly an inhibitor of these enzymes. In a controlled study in healthy adults, a CBD-rich cannabis extract slowed CYP2C19 the most, followed by CYP2C9, CYP3A and CYP1A2, while CYP2D6 was not affected. CBD also inhibits some UGT enzymes and P-glycoprotein, a transporter that moves certain medicines out of cells.

The interaction also works the other way. Medicines that strongly speed up these enzymes, such as rifampicin, carbamazepine, phenytoin or St John’s wort, can lower CBD levels, while strong inhibitors can raise them.

For a broader introduction to how CBD works in the body, see our CBD 101 guide.

Does the dose matter?

Yes. Most of what we know comes from studies with high doses, often several hundred milligrams of CBD per day, similar to the doses used in the prescription medicine Epidiolex. A 2023 review in the Deutsches Ärzteblatt estimated that clinically noticeable interactions should be expected from around 300 mg of CBD per day, and found no evidence of such effects at lower doses.

That does not make lower doses risk-free. A 2026 study by scientists at the US Food and Drug Administration found that about 350 mg of CBD per day, a dose the authors describe as within the range some consumers take, increased levels of the antidepressant citalopram by 43%. Studies at typical supplement doses are rare, so the absence of evidence at low doses is a gap in the research, not a guarantee.

The European Food Safety Authority (EFSA) set a provisional safe intake of about 2 mg of CBD per day for a 70 kg adult in 2026, and stated that the safety of CBD cannot be established for people taking medication.

Common medicines and CBD

The table below lists frequently used medicines and what is known about combining them with CBD. It is not a complete list and it is not a substitute for advice from your doctor or pharmacist, who can take your dose, health and other medicines into account.

Medicine or substance	Commonly used for	Possible effect with CBD	Evidence
Warfarin	Preventing blood clots	Stronger blood-thinning effect (higher INR) and higher bleeding risk	Case reports
Apixaban, rivaroxaban	Preventing blood clots	Possibly higher levels, as both depend on CYP3A4 and P-glycoprotein	Predicted
Clopidogrel	Preventing blood clots	Possibly weaker effect, because it needs CYP2C19 to become active	Predicted
Citalopram	Depression, anxiety	Levels 43% higher after a week of CBD at about 350 mg per day	Human studies
Escitalopram, sertraline, amitriptyline	Depression, anxiety	Possibly higher levels and more side effects, such as drowsiness	Predicted
Diazepam, alprazolam, midazolam	Anxiety, sleep, sedation	Higher levels (shown for midazolam) and more drowsiness	Human studies (midazolam), predicted for others
Zolpidem, sedating antihistamines	Sleep, allergies	More drowsiness when combined	Known additive effect
Morphine	Pain	No clinically meaningful change in levels	Human studies
Oxycodone, fentanyl, tramadol	Pain	Possibly altered levels and more drowsiness	Predicted
Clobazam	Epilepsy	Active metabolite 2.6 to 3.4 times higher, with more drowsiness	Human studies
Valproate	Epilepsy	Higher risk of raised liver enzymes	Clinical trials
Stiripentol	Epilepsy	Levels 30% to 55% higher	Human studies
Tacrolimus, everolimus	Preventing transplant rejection, some cancers	Levels about 2.5 times higher	Human studies
Ciclosporin	Preventing transplant rejection	Possibly higher levels, as it depends on CYP3A4 and P-glycoprotein	Predicted
Omeprazole, esomeprazole, lansoprazole	Heartburn, stomach ulcers	Higher levels (omeprazole about three times higher at a high CBD dose)	Human studies (omeprazole), predicted for others
Atorvastatin, simvastatin	High cholesterol	Possibly higher levels and a higher risk of muscle side effects	Predicted
Losartan, amlodipine	High blood pressure	Modestly higher levels (shown for losartan)	Human studies (losartan), predicted for amlodipine
Sildenafil, tadalafil	Erectile dysfunction	Possibly higher levels, as both depend on CYP3A4	Predicted
Ibuprofen, diclofenac, naproxen	Pain, inflammation	Possibly modestly higher levels	Predicted
Paracetamol	Pain, fever	No interaction documented; both can affect the liver at high doses	Not documented
Metformin	Type 2 diabetes	No interaction documented	Not documented
Hormonal contraceptives	Contraception	Reduced effectiveness is not expected, as CBD slows rather than speeds up the enzymes involved	Not studied
Caffeine	Coffee, tea, energy drinks	Levels almost doubled at high CBD doses	Human studies
Alcohol		More drowsiness when combined	Known additive effect

How to read the evidence column: Human studies and clinical trials measured the interaction in people. Case reports describe individual patients. Predicted means the medicine depends on an enzyme or transporter that CBD affects, but the combination has not been tested. Not documented means we found no reports of an interaction, which does not rule one out.

Medicines that need the most caution

An interaction matters most when a medicine has a narrow therapeutic window, meaning the difference between an effective dose and a harmful one is small. This applies to:

Blood thinners such as warfarin. Case reports describe patients whose warfarin dose had to be reduced after they started CBD, to keep their INR in a safe range.
Medicines that prevent transplant rejection. In human studies, CBD increased levels of tacrolimus and everolimus about 2.5 times. Levels that are too high can damage the kidneys and cause other serious side effects.
Antiepileptic medicines. CBD raises levels of clobazam’s active metabolite and of stiripentol, and increases the risk of raised liver enzymes with valproate. These interactions are well documented because they were studied during the development of Epidiolex.
Some antidepressants. Citalopram labelling already sets a lower maximum dose when it is taken with CYP2C19 inhibitors, and CBD increased citalopram levels to a similar degree as the inhibitor cimetidine.

If you take any of these medicines, do not start CBD without talking to the doctor who prescribes them. They may want to check your blood levels or adjust your dose.

CBD, alcohol and sedatives

CBD can cause drowsiness, especially at higher doses. Combining it with alcohol, sleeping pills, benzodiazepines, strong painkillers or sedating antihistamines can add to that effect. Be careful with driving and operating machinery until you know how the combination affects you.

Do topical CBD products interact with medicines?

CBD applied to the skin, such as a balm, reaches the bloodstream only in very small amounts under normal use. An interaction with medicines is therefore unlikely, although it has not been studied in detail. Products taken by mouth, such as oils, pastes and capsules, are the ones that matter for drug interactions.

Before you use CBD with medication

Tell your doctor or pharmacist that you use or plan to use CBD, including the product and the daily amount in milligrams.
Bring the product or its certificate of analysis, so they can see the actual CBD content and whether it contains THC.
Do not change, reduce or stop your medicine on your own.
Taking CBD and your medicine at different times of day does not reliably prevent an interaction, because the effect on liver enzymes is not limited to the moment you take them.
Watch for signs that a medicine is suddenly working more strongly, such as more drowsiness, dizziness, bruising or bleeding, and contact your doctor if you notice them.

Our view

At Hempika we sell CBD products, and we think the honest message is this: for most people who take no medicines, drug interactions are not a concern. For people who do, CBD is not automatically safe just because it is natural. The interactions described here are real, measurable and manageable, but only when your doctor or pharmacist knows about them.

Frequently asked questions

Can I take ibuprofen with CBD?

No study has tested this combination. Ibuprofen is broken down partly by CYP2C9, which CBD inhibits only weakly in human studies, so a large effect is not expected. If you take ibuprofen regularly, or also take a blood thinner, ask your pharmacist.

Can I take CBD with antidepressants?

Some antidepressants interact with CBD. Citalopram levels rose by 43% in a controlled study, and several other antidepressants depend on the same enzymes. Talk to your doctor before combining them, and do not change your antidepressant dose on your own.

Does CBD interact with blood pressure medicines?

Some blood pressure medicines, such as losartan and amlodipine, depend on enzymes that CBD affects. In a human study, losartan levels rose modestly. If you take blood pressure medicine, ask your doctor or pharmacist before using CBD.

Does CBD affect the contraceptive pill?

This has not been studied. CBD slows rather than speeds up the enzymes that break down contraceptive hormones, so reduced effectiveness is not expected. If you have questions about your contraception, ask your doctor or pharmacist.

Is the grapefruit warning a good guide for CBD?

Only partly. Grapefruit mainly affects CYP3A4, while CBD affects CYP2C19 most strongly. A medicine without a grapefruit warning can still interact with CBD, so the warning is not a reliable way to check.

Can CBD replace my medication?

No. CBD products sold as food supplements are not medicines and must not be used to replace prescribed treatment. The only approved CBD medicine, Epidiolex, is prescribed for specific forms of epilepsy under medical supervision.

Written by: Luka Deržaj
Last updated: September 2026

This article is for general information only and is not medical advice. It does not list every possible interaction. Always consult your doctor or pharmacist before combining CBD with any medicine.

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