Home » CBD and Drug Interactions: An Easy Guide

CBD and Drug Interactions: An Easy Guide



CBD Drug Interactions

While CBD is safe to use, it can potentially mess with other medications you may be taking.

This quick guide should be all you need to safely use CBD even if you have other medications you need to take.

Can CBD interact with other drugs?

Yes. The way that CBD is metabolized by your body can interfere with how your body normally metabolizes other drugs you take. If those other drugs aren’t metabolized properly, they can hang around and stay in your system longer than you want. This can cause negative side effects and complications.

One kind of drug you should pay special attention to is a blood thinner like warfarin. Taking CBD with warfarin can make the warfarin stay in your system for too long without being broken down.

CBD drug interactions aren’t always bad. They can actually be a good thing. CBD can make other drugs more effective, so much so that you can reduce the dosage of those other drugs and thus have less negative side effects to deal with.

The Grapefruit Test is all you need

Thank you to Martin Lee of Project CBD for inspiring the Grapefruit Test. If you haven’t been to Project CBD yet, make sure to check it out. They are running a great site with lots of useful information about cannabis medicine.

As Lee explained in his class CBD 101, CBD interacts with other medications in your body in the same way as grapefruit, only even stronger.

grapefruit 154469 640

Have you ever been told not to take your medication with grapefruit? This is because compounds in grapefruits can interfere with the metabolism of many medications.

CBD does the same thing. But as I said above, the effect is even stronger with CBD.

Do the grapefruit test with your doctor or pharmacist. Ask them: “Should I avoid eating grapefruits or drinking grapefruit juice with this medication?”

They will know exactly what you are talking about. If they say yes, you should avoid grapefruits with your medication, you now know you need to be careful about mixing CBD with those same meds as well. Talk to your doctor about CBD and tell them about it if they say you should avoid grapefruits with your medication.

Alternatively, you can skip the Grapefruit Test and just directly tell your doctor you want to use CBD.

We always recommend you do this anyway, even if your doctor doesn’t work directly with cannabis. Medical schools typically don’t educate physicians about the endocannabinoid system, the most widespread receptor system in the human body. But that doesn’t mean we shouldn’t educate them about it!

If your doctor is aware of your CBD usage, he may decide to monitor your blood work more closely or tell you to avoid taking CBD at the exact same time as your other medications.

Play it safe and keep CBD safe.

If you take other medication, speak with your doctor before you start taking CBD.

~ Vadim the CBD Professor    

How CBD reacts when it interacts with other Drugs?
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How CBD reacts when it interacts with other Drugs?
CBD has activated interactions with other Drugs too. It's really important to know how it reacts & what are reactions.
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CBD School
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    • Hey Joe. Thanks for your question. I am not a doctor or medical professional so I would not be able to answer your question. I recommend you speak with your prescribing doctor before taking CBD oil. Some good places to research drug interactions with CBD would be this post as well as this post from Project CBD.

    • Hey Julie. Thanks for your question. I think CBD oil is definitely worth a try if you have epilepsy. But I always recommend checking with your doctor first and working alongside their supervision, especially if you are taking other medication already for epilepsy. Please let me know if you have other questions and I will do my best to help 🙂

    • I haven’t heard of the cantab tablets but have heard great things about CBD pure. I take and sell HempWorx and live in KY whuch is a heavily opiate addicted state. I want to educate people on how CBD can help, especially with the Feds closing the doors on several pain clinics lately. The doctors who are “helping” these misplaced patients find solutions will not mention CBD and it is so frustrating. Congratulations on getting free of opiates. I used Suboxone which was harder to come off of than the opiates, especially cold turkey. Message me if you have any advice on how I can reach some of these patients without sounding like I just want to sell my product to them.
      Best Wishes,

  • Hi,

    Do you know of information about interactions with blood thinners specifically, metoprolol or where I can find the information?

    Thank you

    • Hey Pauline. Thanks for your question. CBD can alter the blood levels of another drug being taken. I always recommend speaking to your doctor or pharmacist first before you start using CBD, just to be on the safe side. Most people do not have serious problems with drug interactions but again, always better to be safe.

    • Hey Kristin. Thanks for your question. I wish I could answer that but it’s completely outside my realm of expertise. My vet of choice for these types of questions is Gary Richter. He is a well experienced veterinarian who has a lot of experience working with CBD. Make sure to Google him and I bet he can answer you question. I hope that helps and please let me know if you have any other questions 🙂

    • Hey Marty. Thanks for your question. Unfortunately I do not know the answer as I am not a veterinarian. My veterinarian of choice who has a lot of experience working with cannabis is Dr. Gary Richter. You may also be able to ask your vet this question and get an answer. I hope that helps.

  • Have you heard of unwanted side effects for taking cbd oil with biologics and methotrexate? I know it may change the way my body metabolizes the meds I take and I have to have frequent blood-work for my liver & kidney function. The biologics and methotrexate have become less effective, either due to progression of my disorder or because my body has become resistant over the past 10 years. I’m in constant, severe pain, looking for relief where ever it may be found.

    • Hey Jeris. Thanks for your inquiry and I am sorry to hear about your condition. Unfortunately, I have never heard of unwanted side effects from this specifically. I recommend to speak with a doctor as soon as possible.

    • Hey Mrs. Storkey. Thanks for your inquiry. Unfortunately I cannot answer that as I am not a doctor. Please check with your doctor or pharmacist. What I can tell you is that most people do not have problems with drug interactions and CBD. Still I urge you to be cautious and check with a medical professional. Let me know please if there is anything else I can help you with 🙂

    • Hey John. Thanks for your question. Unfortunately I cannot answer this as I am not a doctor. Please check with your doctor or pharmacist. What I can tell you from my anecdotal experience is that most people do not have problems with drug interactions and CBD. Still I urge you to be cautious and check with a medical professional. Let me know please if there is anything else I can help you with 🙂

  • I had a Cortisone injection in my left knee on 25/4/18 will I suffer any ill effects if I take CBD oil?

    • Hey William. Good question, I haven’t had that one before. Remember I am not a doctor so my opinion is not professional. I would not think this would cause any problems but the best thing to do is just check with your doctor first. Let them know why you want to take the CBD and just make sure it’s OK to take alongside anything else you may be taking as well as the Cortisone injection. I’ve had those injections before as well. I hope you found relief from them. Let me know if you have any other questions I can do my best to help answer for you 🙂

  • I couldn’t eat grapefruit whilst I was on statins, but have stopped statins by doctor as they didn’t agree with me. I take other heart meds, I wonder if they would interfer with the CDB.

    • Hey Morag. I would definitely get this checked with your doctor. Let your doctor know you are taking CBD and you want to make sure it’s ok with your other medications. Let me know if you have other questions and I’ll do my best to help.

  • Can you recommend any veterinarians in the Seattle area that are familiar with the use of CBD oil? I recently adopted an older dog with hypothyroidism, arthritis, and muscle atrophy in his hind legs. Here’s a bit of a mess to say the least. Two weeks ago I started him on CBD oil (NuLeaf) after watching your videos. He’s at 5 drops, twice a day now and weighs about 90 pounds and is still under weight. He seems extra tired and grumpy the last few days and I’m wondering if the oil could be affecting his thyroid medicine. I would like to find a holistic vet to treat his pain and arthritis. Any recommendations would be appreciated,
    thanks, Claudia

    • Hey Claudia. Thanks for your inquiry. I have no way to know if it’s interacting with his other medicine as I’m not a vet. But it’s a good thing to get checked out so I’m glad to hear you asking this question. I know a very good vet in the SF Bay area named Dr. Gary Richter. It’s possible he may be able to do a phone consultation with you. Dr. Richter is who I would recommend. Sorry to hear about your pup, I know that’s frustrating. If you are consistently noticing a negative side effect with him after using CBD, it may not be the right tool for him. Let me know if you have other questions and I will do my best to help 🙂

  • I have a sick wife that has Asthma & leukemia , my question is she is on alot of medicine and I need to know if CBD will help her be herself again or close so she can go out and have a life .

    • Hey Hector. Thanks for your inquiry. I am sorry to hear about your wife. I cannot help you with this inquiry since I cannot provide medical advice. I urge you to please discuss this and get the OK from your doctor before using CBD.

  • Hi there
    Just started the CBD last week.
    5 mgs a day.
    I also have been and still am on a strong med called oxycodone.
    Have had croniv back pain for over 10 yrs. Really serious fibro for over 30 yrs.
    And lupus.
    I also take lerica.
    I’m going to try and decrease these horid perscribed meds.
    I have cronic pain most of the day and night.
    One week with CBD , but no difference as of yet .
    Is there something wrong I’m doing,?
    Is it just time or increase CBD dosage?
    P.s. I am scared to ask my Dr. He’s against all canibis products.

    • Hey Debbie. Thanks for your inquiry and clear explanation. I appreciate that. Sorry to hear about the pain. I know that it’s hard. As long as you feel comfortable, you can increase the CBD dose to see if that would help. Keep in mind if it’s really intense pain, CBD may not be effective enough as a painkiller. However 5mg is generally considered a small dose. Sorry to hear your doctor isn’t open to it. But it’s just because it’s not FDA approved. I think this will change soon. Since you’re using multiple medications, I recommend you still get the OK from your doctor to use CBD. Please let me know how else I can help and I’ll do my best 🙂

  • If CBD is built up in your system over a few days, can the residual still have an effect on how p450 metabolizes drugs? I have been taking Ambien for sleep and tried CBD. Took a large dose one day (30mg) and 5mg 2x the following day. I ended up feeling drugged all day the following 2 days. Rather than the 10 or we hours Ambien is supposed to stay in your system.

    CBD supposedly stays in your system 3-5 days. I’m wondering if the residual could still have an effect on the Ambien.

  • Can I take CBB oil with my norco for post lisfranc foot surgery pain? I feel it will help wth the inflammation of the trauma. The pain meds are not that effective and I am struggling with the pain, my dr didn’t really have an opinion either way….

    • Hey Blu. Thanks for your question. Sorry to hear about your situation. I don’t have an answer to your question as I’m not a doctor. I would speak again to your doctor about it and or get a second opinion from a different doctor. You can speak with your pharmacist as well.

  • Hi Vadim,

    I won’t ask whether I can safely take CBD oil with my meds because I know (and you’ve repeatedly said) that you’re not a doctor or a pharmacist. I appreciate your ethics in that regard. I wish people would stop asking you to comment outside your scope of expertise. Don’t they know that if you advise them on such things it would endanger all the work you’re doing?

    The question I do have is whether or not you can comment on how long it might take to notice the effects of CBD usage? I have just begun (today) my CBD oil usage and I’m not sure how to decide that I’ve tried it at a certain dosage long enough and should change the dose. Is it, generally speaking, something I would notice right away (say, an hour after dosing) might it take a day or two to notice effects?


    • Hey, thanks for your comment. I appreciate you understanding why I cannot provide medical advice. I’m happy to help with your question based on my own experience with CBD. First off, it will typically depend on what delivery method you’re using. How are you taking it, in this case?

      • Oh sorry! Stupid if me not to give you all the information. I’m taking a .5mL dose of an olive oil + CBD oil tincture. The label says it’s 500+mg in a 60mL bottle. I’ve only had one dose but the label says I’m able to take 1 to 4 doses, twice per day. I’m trying to take particular notice of any alteration to my symptoms (I have Parkinson’s and PTSD) in order to determine how much/often I should dose. Tentatively, I can say that I’ve been a bit happier since taking that first dose (I experience quite a bit of anxiety) but that may be wishful thinking. My goal in CBD use is to reduce anxiety, which has become quite debilitating. If I have positive effects in other ways, so much the better. My psychiatrist reacted positively when I asked about CBD usage and didn’t hesitate to recommend a “green card” for medical marijuana. However, I don’t like the experience of being high, so I chose CBD instead.

        • Great, thanks for the detailed information. One more question. What’s the serving size mg of CBD per dose? It sounds as if you are taking a typical serving size. I am pleased to hear you are working on this alongside a medical doctor. As long as you’re comfortable and with your doctor’s awareness, you can decide if you want to increase the dose gradually. Most people experiment slowly until they find their sweet spot and what works best for them. CBD is generally pretty subtle so I’m not surprised that you’re not feeling anything drastic. With an oral dose the effects are typically felt within 1 hour. Let me know if you have more questions and I will do my best to help.

  • Hi, I was wondering why the THC is needed at all. All new to me and I am considering using CBD oil for low grade aches/pains from exercise, but mostly for sleep disturbance (wakefulness). When I looked on the Project CBD website it mentioned something to the effect that the goal was to find the right dosage of CBD with ‘as much THC as a person is comfortable with’…
    My question is if the effects of CBD are enhanced with THC (or lessened w/o THC)?

    • Hello Tammy. Thanks for your excellent question. THC is not absolutely necessary. Some evidence has shown that THC and CBD work well together – this is the theory of the entourage effect. However plenty of people have good results using THC or CBD separately. THC can have some side effects which people do not like. It’s all about finding what works best for you, as each person’s case is different. As always, we recommend speaking with your doctor before using CBD or THC.

  • Hi me again, I have two other questions wondering if you can clarify to any degree. I have read some of the research lit on CBD and other articles that extrapolate this info, but I do not have a clear idea on two particular facets:
    1. CBD is known to affect the human cytochrome P450 system, at what dosage or level does this occur? Much of the research lists extremely high dosage levels.. many, many mg/kg – not near the recommended levels of use I have seen for general dosing. Is there a known level where the effects on the P450 system begin to occur in humans?
    2. Can or does CBD use lead to a tolerance whereby increasing doses are needed for the same effects – or not?


  • I have successfully slowly weaned myself off Palexia (an Opiod) by using CBD oil. However, my pain level is high at present (hot weather isn’t helping). I am prescribed Solpodol and Paracetamol and when taking Palexia I seldom needed them! I really need to know exact detail of the CBD oil for my severe Fibromyalgia, CFS and 2 buldging discs. Can you help me please? Thank you.

    • Hey Joy. Thanks for your comment. I’m not able to answer medical questions. But I can help you with general questions about CBD oil. Please consult with your doctor regarding medical questions and before using CBD oil. Thanks.

  • Know u can’t give specific answers, but in your experience does the reaction between warfarin and cbd any less when taken at different times. My husband has significant arthritis problems and benign tremors and would benefit from trying cbd but also must take warfarin due to having a 16 inch blood clot. Is it worth the risk? Thanks


  • Don’t mix Clonazepam & CBD at any dose. Study has been done on anti-seizure drugs for CBD liver enzyme interactions. I found out the hard way as I was using CBD to taper off Zoloft (no interactions) and it helped tremendously until I suffered exploding head syndrome and was diagnosed with severe anti-depressant discontinuation syndrome and had to go back on 50mg Zoloft to stop the major brain lightening strikes. Also had to go back on clonazepam so I could sleep until zapping stopped. I never stopped taking CBD (30mg 25:1). Unfortunately Clonazepam is one of the meds that doesn’t get backed up in the blood waiting for CDB to stop inhibiting CYP 3a4 enzyme (only enzyme that metabolizes clonazepam) anywhere form 0 to 30% is excreted. So I started on a roller coaster of one day being fine then having benzo withdrawal the next day. Once I figured it out and stopped CBD it took a few days to get better as CBD has a long half life so it can take 3-5 days until you get a static blood level of clonazepam.

    https://www.projectcbd.org/science/cannabis-pharmacology/cbd-drug-interactions-role-cytochrome-p450. Scroll to bottom and hit link “AED Possible interatcions with CBD”.

    • Hi Laura. Thank you for your question. Please speak to your doctor before using CBD. Using CBD topically would be less likely to cause an interaction as compared to using CBD internally. Still it’s important to speak to your doctor about CBD because I cannot provide medical advice. Best of luck to you.

    what equivalent has CBD brother in stock?

  • Out of all the questions people have asked you seem to have the same answer. That is you don’t know consult your doctor repeatedly the same answer over and over again. So tell me what is the purpose of your site. ?

    • Hey Rich. Thanks for your question. CBD School is an information resource for all things CBD, hemp, and cannabis. I can’t answer medical questions. But I will always help as much as I can, with product related questions mostly. Thanks for visiting and have a great day 🙂

  • Does TOPICAL CBD have any contraindications or drug interactions? I.e if I got a CBD infused Massage do I have to worry about anything?

    • Hey Tanya. Thanks for your excellent question. No, you should not have to worry about any interaction with a medication you are taking since the topical CBD from the massage is not entering your bloodstream. The only interaction to be possibly concerned with is with something else you are using on your skin, though I never heard of anyone having a problem with this. Let me know if you have any follow up questions 🙂

  • I have m s & a degenerative spine, also severe knee & hip pain. My pain killers do not work. I am also diabetic on Metformin. I am desperate to have less continuous pain. My g p does not know & said speak to my pharmacist. I am very keen to start on CBD+ oil. What can I do? Thank you.

    • Hello Sara. Thanks for your comment. I agree with your doctor. It would be best to speak with your pharmacist as they know all of your current medications. They may be able to suggest a different time of day for when to take the CBD so that it doesn’t interact with your other medications. You pharmacist and doctor may also want to monitor you while you take the CBD to make sure there are no negative interactions with the medications you are currently taking.

  • Thank you for sharing such a important information, as rarely people know this use of CBD. I know about CBD but not aware the CBD can be use in this way as well.

    • Hey Matt. Thanks for your question. It’s important to be careful about using CBD with Warfarin. We advise speaking to a doctor before starting. The problem is that CBD can alter the normal way your body processes the Warfarin, thereby changing its effects. Please speak with your doctor before using CBD if you are taking Warfarin. Your doctor may want to monitor you closely if you decide to use CBD to make sure there are no issues with a drug interaction.

  • I take two meds for prostate ,desmopressin tab and finasteride tab.do these two conflict with cbd. I have arthritis and was thinking about cbd for pain.