CBD can interact with other medicines. It is broken down by the same liver enzymes that handle a large share of prescription drugs, so it can raise or lower the level of another medicine in your blood, and a few combinations are well documented. For most healthy adults taking CBD as a food supplement alongside nothing stronger than the odd paracetamol, this is not a practical concern. For anyone on regular medication it is the first question to ask, and the answer is a short conversation with your pharmacist before you start. This guide tells you what that conversation is about.
We cover how the interactions happen, the medicines that matter most, what the clinical trials have actually documented, the groups the regulators advise not to take CBD at all, how to take CBD more safely if your pharmacist is happy, and how we handle the question with our own customers. We make our CBD at our laboratory in York Science Park, our scientific adviser is a consultant neurologist, and we would rather lose a sale than have you combine something you should not.
Table of Contents
- How CBD interacts with medicines
- The medicines that matter most
- What has actually been documented
- Who should not take CBD with medication
- Taking CBD more safely alongside medicines
- Creams, balms and patches
- How we do it at HempWell
- Frequently asked questions
How CBD interacts with medicines
Most medicines are cleared from the body by liver enzymes of the cytochrome P450 family, chiefly CYP3A4 and CYP2C19, and by transporters such as P-glycoprotein. CBD is both processed by those enzymes and, at sufficient doses, slows them down. A review of the prescribing data for pharmaceutical CBD concluded that “given CBD effects on common biological targets implicated in drug metabolism (e.g., CYP3A4/2C19) and excretion (e.g., P-glycoprotein), the potential for DDIs with commonly used medication is high”, and that CBD “is implicated as both a victim and perpetrator” of interactions (Brown and Winterstein, 2019).
Two things temper that. First, the documented interactions come from prescription CBD at 10 to 20mg per kilogram a day, many times the amounts sold as supplements; whether a 20mg daily dose does anything measurable to another drug is not well studied either way. Second, the direction matters: slowing an enzyme raises the other drug’s level, which is only dangerous when that drug has a narrow safe range. That is why the list below is short and specific rather than “everything”.
The medicines that matter most
| Medicine group | Why it matters | What to do |
|---|---|---|
| Anticoagulants (warfarin) and some antiplatelets | Narrow safe range; CBD may raise warfarin levels and INR | Do not start CBD without your GP or anticoagulant clinic; extra INR checks if they agree |
| Anti-epileptic drugs (clobazam, sodium valproate, others) | The best-documented interaction: CBD raises the active metabolite of clobazam; sedation and liver effects seen with valproate | Specialist decision only |
| Sedatives, sleeping tablets, strong painkillers, alcohol | Additive drowsiness rather than an enzyme effect | Avoid combining, especially before driving |
| Immunosuppressants (tacrolimus, ciclosporin) and some transplant or cancer medicines | Narrow range, CYP3A4-dependent | Specialist decision only |
| Medicines with a grapefruit warning | Grapefruit blocks the same enzymes; the warning is a useful proxy | Treat CBD as you would grapefruit until your pharmacist says otherwise |
| Antidepressants, antipsychotics, beta-blockers, statins | Metabolised by the same pathways; interactions theoretical at supplement doses | Mention CBD to your pharmacist; start low; watch for drowsiness or unusual side effects |
| Paracetamol, ibuprofen, antihistamines, the pill | No clinically important interaction documented at supplement doses | Normal precautions |
What has actually been documented
- Epilepsy medicines. A review of six interaction trials of prescription CBD found “an overall low potential for DDIs between CBD and other ASDs, except for CLB” (clobazam), where CBD raised the levels of both drugs’ active metabolites, so a lower clobazam dose may be needed (Patsalos et al., 2020).
- Where the serious side effects came from. The meta-analysis of placebo-controlled CBD trials found that the liver-test changes, sleepiness and sedation “were limited to childhood epilepsy studies, where CBD may have interacted with other medications such as clobazam and/or sodium valproate”, and concluded that “interactions with other medications should be monitored carefully” (Chesney et al., 2020).
- Liver enzymes on their own. In healthy adults taking around 350mg a day for four weeks, 5.6% developed liver enzyme rises against none on placebo (Florian et al., JAMA Internal Medicine, 2025). Medicines that also load the liver make that worth knowing. Our guide to CBD oil side effects covers the dose-by-dose picture.
- No conversion to THC. Pure CBD does not turn into THC in the body (Sholler et al., 2022), so there is no hidden THC interaction from a THC-free product.
Who should not take CBD with medication
The UK Food Standards Agency’s precautionary advice, which we apply to our Irish customers too, is that CBD food supplements are not recommended for people taking any medication, alongside children, anyone pregnant or breastfeeding and anyone trying to conceive. In practice, “any medication” covers a lot of healthy adults on a single routine prescription, so we read it as: do not start without asking. If your pharmacist or GP is comfortable, the steps below keep the risk small. If you are on any of the narrow-range medicines in the table, treat the answer as no unless a specialist says otherwise.
Taking CBD more safely alongside medicines
- Ask first, with the product in hand. Pharmacists are the right people for this and the conversation takes five minutes. Bring the CBD content per serving.
- Start low and stay low. A few milligrams a day, well under the Food Safety Authority of Ireland’s 70mg guidance for healthy adults. Interaction risk rises with dose.
- Separate the timing. Taking CBD a few hours apart from your medicine will not remove an enzyme interaction, but it does reduce additive drowsiness.
- Watch for the signs. Unusual drowsiness, dizziness, bruising or bleeding on anticoagulants, or any new symptom after starting. Stop and ask.
- Tell every clinician. Blood tests, new prescriptions, surgery: mention CBD as you would any supplement.
- Use a product with a lab report. A known CBD content, and no THC, is the starting point for any sensible risk assessment. Ours are on our lab reports page.
Creams, balms and patches
CBD applied to the skin reaches the bloodstream in very small amounts, which is why topicals are regulated as cosmetics and why interactions are not a practical concern with a cream or balm. Our guide to topical versus transdermal CBD explains the difference. If you are on narrow-range medication and want to try CBD at all, a topical is the lower-risk route, with the usual advice to tell your pharmacist.
How we do it at HempWell
- We ask the question for you. Our dosage guide, product pages and customer care team all say the same thing: on regular medication, check with your pharmacist first. Our FAQ page has the short version.
- Known contents. THC-free CBD with the exact mg per ml stated and a graduated pipette, so a pharmacist can assess a real number.
- Medical oversight. Our health content is written with Professor Mike Barnes, a consultant neurologist, as our scientific adviser.
Questions about a specific medicine? Ask us and we will tell you honestly if the answer is “ask your pharmacist”, because often it is.
Frequently asked questions
Can I take CBD with my medication?
It depends on the medication. With paracetamol, ibuprofen or antihistamines, generally yes. With anticoagulants, anti-epileptics, immunosuppressants or anything with a grapefruit warning, not without your GP, specialist or pharmacist agreeing. For everything else, ask your pharmacist and start low.
Can I take CBD with blood thinners?
Not without medical advice. CBD may raise warfarin levels, and the safe range is narrow. If your clinic agrees, expect closer INR monitoring.
Can I take CBD with antidepressants?
Antidepressants share CBD’s metabolic pathways, so an interaction is possible but not well documented at supplement doses. Mention CBD to your pharmacist, start low, and watch for added drowsiness.
Does CBD interact with blood pressure tablets?
CBD itself can lower blood pressure slightly, so added to medication it could cause light-headedness. Ask your pharmacist and start very low if they agree.
Can I use CBD cream with my medication?
Very little CBD from a cream or balm reaches the bloodstream, so interactions are not a practical concern. Tell your pharmacist anyway.
Is it safe to take CBD before surgery?
Tell the anaesthetist and follow their instruction; many ask you to stop supplements beforehand. CBD’s effect on drowsiness and liver enzymes is why.