CBD alongside medication: not a question for the internet.

Why can a supplement affect a medicine?

Your liver breaks down medicines with a set of enzymes. The best-known family of these is called cytochrome P450, often shortened to CYP in patient leaflets. Those enzymes determine how quickly a medicine leaves your blood again, and so how much of it stays active.

Some substances slow those enzymes down. If the breakdown slows, more of the medicine stays in your blood than intended, and that can have the same effect as too high a dose. The other way round, a substance can speed the enzymes up, so that a medicine disappears too quickly and does too little.

Cannabidiol is known to affect enzymes from this family. The Dutch Medicines Evaluation Board (CBG) therefore explicitly names interactions as a point of attention with CBD.

EFSA takes it into account too. When that authority set a provisional safe intake for CBD in February 2026, people who take medication were explicitly left out: for that group, safety remains uncertain. So for you, there isn't even a guideline value to hold on to.

Do you know the grapefruit warning?

Quite a few patient leaflets say you shouldn't eat grapefruit with that medicine. That is exactly the same mechanism: substances in grapefruit slow down one of those liver enzymes, so the medicine behaves differently from what the dose was set for.

It is a useful comparison, with one caveat. Two substances acting on the same enzyme family doesn't mean they are equally strong or cause problems with the same medicines. So use the grapefruit rule to understand the idea, not to draw your own conclusions.

Which medicines does this apply to?

This is where we deliberately stop. A list on a brand's website looks helpful, but it is misleading: hundreds of medicines are broken down this way, the strength of the interaction differs per medicine and per dose, and your particular combination of medicines changes the picture again.

The literature mentions, among others, blood thinners, certain epilepsy medicines and medicines with a narrow margin between too little and too much as points of attention. See that as an illustration of the kind of medicines where it matters more, not as the list your medicine is or isn't on.

Why the pharmacist and not your GP?

Both are good, but the pharmacist has one advantage: they have your complete medication record in their system, including whatever a specialist prescribed. Monitoring interactions is exactly what that system is made for.

Bring a concrete question. Say which product you want to use, how many milligrams of CBD it contains and how much you plan to take. Those numbers are on our product pages, so you can simply take them along or show them.

What should you watch for if you do start?

If you have started after talking to your doctor or pharmacist, watch for changes you would normally put down to your medicine: more drowsiness than usual, a different effect from your medication, or new complaints without a clear cause. Report signals like these to whoever prescribes your medication, and don't wait weeks to do so.

Who else should take extra care?

Besides people who take medication, the European Food Safety Authority also names women who are pregnant or breastfeeding, people under 25 and people with a liver condition as groups for whom safety has not been established. That last group is especially relevant here, because the liver is exactly the organ where this interaction takes place. Children are not part of the target group for CBD products in any case.

The full explanation per group is on the safety page, and the wider overview is in the knowledge base.