Does CBD Oil Affect Blood Clotting? CBD and Blood Thinners (2026)

Last updated: September 2026.

The short answer

In healthy people taking normal amounts, there is no good evidence that CBD oil causes bleeding or stops blood from clotting properly. The real concern is medication: CBD can change how the body breaks down some blood thinners, especially warfarin, which can make them stronger than intended. If you take any blood-thinning medicine, speak to your doctor or pharmacist before taking CBD, and don’t start or stop CBD without telling them.

How blood clotting works (in brief)

When you cut yourself, small blood cells called platelets clump together at the injury, and proteins in the blood called clotting factors form a mesh that seals the wound. People at risk of dangerous clots, for example after a stroke, with atrial fibrillation or after a deep vein thrombosis, are often prescribed medicines that slow this process down. The balance matters: too little clotting means bleeding, too much means clots.

Does CBD oil thin the blood?

CBD is not a blood thinner, and it is not sold or used as one. Some lab and animal studies have looked at whether cannabinoids affect how platelets clump together, with mixed results. There is no convincing evidence that the amounts of CBD in food supplements, typically 10 to 50mg a day, have a meaningful effect on clotting in healthy people.

CBD and blood thinners: the real issue

The main risk comes from how the body processes CBD. CBD is broken down in the liver by a family of enzymes called CYP450. Many medicines, including several blood thinners, are processed by the same enzymes. CBD can slow some of these enzymes down, which can mean more of the medicine stays in your blood for longer.

Warfarin

Warfarin is the best-documented example. Doctors have reported cases where patients on warfarin started CBD and their INR (the blood test that measures how long blood takes to clot) went up, meaning their blood was clotting more slowly than intended. In one published case, a patient’s warfarin dose had to be lowered by about 30% after starting a prescription CBD medicine (Grayson et al., 2018). Those cases involved high medical doses of CBD, but it is the reason warfarin users need to be careful.

Newer blood thinners (DOACs)

Medicines such as apixaban (Eliquis) and rivaroxaban (Xarelto) are also partly processed by CYP450 enzymes. There is much less data on CBD with these medicines, so the cautious approach is to treat them the same way: check with your doctor or pharmacist first.

Antiplatelet medicines

Clopidogrel (Plavix) needs to be activated by a liver enzyme that CBD can also affect, so in theory CBD could change how well it works. Low-dose aspirin is processed differently, but anything that affects bleeding is worth mentioning to your GP.

If you take a blood thinner and want to try CBD

• Talk to your GP, pharmacist or anticoagulation clinic first.
• If they agree, start with a low amount and keep it steady from day to day.
• Your doctor may want to check your INR more often for the first few weeks (if you take warfarin).
• Don’t suddenly stop or change your CBD amount without telling your doctor, as that can change your INR too.
• Watch for signs of bleeding: unusual bruising, bleeding gums, nosebleeds that won’t stop, blood in urine or stools. Contact your doctor straight away if you notice any.

Other supplements that can affect bleeding

CBD is not the only supplement to think about. Fish oil, high-dose vitamin E, ginkgo, garlic supplements and turmeric can all affect bleeding, especially alongside blood thinners. If you take several supplements, tell your doctor about all of them. Our guide to CBD and turmeric covers that combination in more detail.

CBD before surgery or dental work

As a precaution, stop taking CBD and other supplements that may affect bleeding at least two weeks before planned surgery, and tell your surgeon or dentist what you take.

What to bring when you talk to your GP or pharmacist

A five-minute conversation is all it usually takes. To make it quick and useful, bring:

• the CBD product itself, or a photo of the label showing the CBD content
• a list of every medicine you take, including the dose
• any other supplements you take, such as fish oil, turmeric or ginkgo
• your most recent INR result if you take warfarin

Ask whether CBD is suitable alongside your medicines, and whether you need any extra blood tests if you go ahead. Your pharmacist can check interactions on the spot, and they are often the easiest person to ask.

Signs of bleeding to watch for

Anyone taking a blood thinner should know the signs of bleeding, whether or not they use CBD. Contact your GP or pharmacist promptly if you notice:

• bruising that appears without a clear reason, or is larger than usual
• nosebleeds that last longer than 10 minutes
• bleeding gums
• blood in your urine (pink, red or dark brown) or in your stools (red or black)
• heavier periods than normal
• cuts that take longer than usual to stop bleeding

If you have severe bleeding, a serious fall or a head injury while taking a blood thinner, seek emergency help straight away.

CBD creams and blood thinners

CBD creams and balms work on the skin where you apply them, and only a small amount of CBD is thought to reach the bloodstream. That makes an interaction much less likely than with oils, gummies or capsules. Even so, if you take a blood thinner, mention any CBD product to your pharmacist, including creams. Our CBD creams list the CBD content on every product.

Food and drink that can affect warfarin

If you take warfarin, CBD is only one of several things that can change your INR. Your clinic will usually also mention:

• Vitamin K foods such as kale, spinach, broccoli and sprouts. You do not need to avoid them, but keep the amount you eat fairly steady from week to week.
• Cranberry and grapefruit juice, which are often advised against in large amounts.
• Alcohol, especially binge drinking, which can make your INR less stable.
• New supplements or herbal remedies of any kind, which is where CBD fits in.

The common thread is consistency. Sudden changes, such as starting a new supplement or changing your diet, are what make INR harder to control, so tell your clinic about any change.

Frequently asked questions

Does CBD oil affect blood clotting?

In healthy people taking normal supplement amounts, there is no good evidence that it does. The concern is with blood-thinning medicines, especially warfarin, where CBD can raise the level of the medicine in your blood.

Can I take CBD with warfarin?

Only with your doctor’s agreement. CBD can raise INR in people taking warfarin. If your doctor is happy for you to try it, they may check your INR more often at first.

Can I take CBD with apixaban or rivaroxaban?

There is little research, and an interaction is possible because these medicines share liver enzymes with CBD. Check with your doctor or pharmacist first.

Does CBD raise or lower blood pressure?

Some small studies found a single dose of CBD slightly lowered blood pressure, especially under stress. If you take blood pressure medication or have low blood pressure, speak to your doctor first.

Is CBD safe for people with heart conditions?

Many people with heart conditions take several medicines, so the interaction risk is higher. Always ask your cardiologist, GP or pharmacist before starting CBD.

Can I take CBD with aspirin?

Low-dose aspirin is an antiplatelet medicine. There is little research on CBD and aspirin together, so speak to your GP or pharmacist first, especially if you also take another medicine that affects bleeding.

Can I take CBD with clopidogrel?

Clopidogrel is activated in the liver by an enzyme that CBD may affect. The evidence is limited, but it is a good reason to check with your pharmacist before combining them.

Should I stop CBD before an INR blood test?

Do not change your routine just before a test without telling your clinic. If you are starting, stopping or changing CBD, let your anticoagulation clinic or GP know, as they may want to check your INR more often for a while.

Can I take CBD gummies on blood thinners?

The same advice applies to gummies as to oil: speak to your GP or pharmacist first. The form of CBD does not change the possible interaction, though the amount you take does.

Does CBD affect platelets?

Some laboratory studies suggest CBD may have a small effect on how platelets behave, but there is not enough human research to know whether this matters at the amounts in a food supplement. The main known concern is CBD changing how your body processes blood-thinning medicines.

Buying CBD in Ireland

If your doctor is happy for you to try CBD, choose a product with a clear amount of CBD per drop, so you can keep your intake steady and tell your doctor exactly what you take. Our 10% CBD oil gives 5mg per drop, every batch is independently lab tested, and the reports are on the product page. See our dosing guide for how to start low.

Disclaimer: CBD and functional mushrooms are sold as food supplements. They are not intended to diagnose, treat, cure or prevent any disease and are not a substitute for medical advice. Always consult a healthcare professional before starting a new supplement, especially if you take medication, are pregnant or breastfeeding.

References

1. Grayson, L. et al. (2018) “An interaction between warfarin and cannabidiol, a case report.” Epilepsy & Behavior Case Reports
2. Brown, J.D. and Winterstein, A.G. (2019) “Potential adverse drug events and drug-drug interactions with medical and consumer cannabidiol (CBD) use.” Journal of Clinical Medicine
3. Huestis, M.A. et al. (2019) “Cannabidiol adverse effects and toxicity.” Current Neuropharmacology
4. Jadoon, K.A. et al. (2017) “A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study.” JCI Insight