Does CBD oil act as a blood thinner by itself? How does CBD oil interact with anticoagulants like warfarin? Should you stop taking CBD before an operation? Find out these answers and more in this comprehensive guide on CBD oil and blood thinners! If you've been prescribed warfarin (an anticoagulant) and are wondering if you can also take CBD oil, read this post before proceeding to know the risks of this drug interaction. The short answer is – no, in most cases cannabis and specific cannabinoids do not seem to act as strong blood thinners.
Can CBD Oil Thin Your Blood?
Given what it can do, it’s no wonder people are concerned about the possible side effects of CBD oil. Researchers and scientists are steadily building knowledge about CBD and other cannabinoids to find out how and to what extent they relieve pain, help our stress responses, regulate sleep, and more.
More is being discovered about CBD and cannabinoids all the time, which is why questions about its side effects keep coming up. We do know that it can interact with some medications and have dire consequences for people with heart issues and other risk factors.
Does CBD oil act as a blood thinner by itself? How does CBD oil interact with anticoagulants like warfarin? Should you stop taking CBD before an operation? Find out these answers and more in this comprehensive guide to CBD oil and blood thinners.
The Basics Of Blood Thinners
Arteries, veins, and capillaries are the three kinds of blood vessels that transport blood around the human body. The average speed of blood is between 3 and 4 miles per hour – pretty fast considering the average height of an adult human male is 176.5 centimeters, or 0.001 miles.
When your body needs to stem blood flow – for instance, when you get a cut or an injury – it makes cells called platelets that group together to create blood clots. You might have heard of clotting issues like Deep Vein Thrombosis and the buildup of plaque on artery walls that can lead to pulmonary embolisms and other serious health problems.
Blood thinners are meant to address and prevent these issues. Blood thinners don’t actually make your blood thinner or dilute it in any way. They work by stopping the formation of blood clots and preventing existing blood clots from getting any bigger. People who have had heart attacks or a stroke are prescribed blood thinners to prevent future ones.
The human body needs to be able to thin blood and create clots based on new conditions. According to one study , cannabidiol (CBD) “inhibits CYP2C19, increasing levels of the active metabolite of clobazam threefold.” The researchers also add that smoking marijuana could have “serious interactions with drugs like warfarin,” warfarin being a common anticoagulant sold under the name Coumadin among others.
What this basically indicates is that there is very likely a possibility that CBD and other hemp extracts can inhibit the inhibitors, essentially wrecking the efficacy of blood thinners like warfarin. But what about people who aren’t on blood thinners? Should they be worried about taking CBD oil?
CBD Oil & Thinning Blood
The danger with combining CBD oil and blood-thinning medications is that both can act as blood thinners, thinning your blood more than your doctor intended. That would seem to indicate that CBD oil has anticoagulant effects on its own.
A study found that cannabis sativa and the cannabinoids tetrahydrocannabinol (THC) and cannabinol (CBN) “ display anticoagulant activity ” when introduced in an animal specimen. CBD wasn’t singled out with the other two extracts. So do CBD products have the same effect as the two cannabis plant extractions mentioned in that study?
The widely accepted answer is that yes, CBD oil has some effect on the thinness of your blood. Harvard Health Publishing , for example, has said that CBD can “increase the level of blood thinning and other medicines in your blood by competing for the liver enzymes that break down these drugs.”
They do go on to mention that grapefruit is known to have a similar effect. The National Health Service (NHS) in the UK instructs readers taking warfarin to avoid grapefruit juice but also mentions some different blood-thinning medications that present less of a risk when grapefruit juice is present in the body and competing with medication in the liver’s enzyme system.
If we follow the logic backward, it appears reasonable to draw the conclusion that anyone worried about a negative drug interaction, bleeding complication, suffering from heart disease, having a history of strokes, or otherwise concerned or vulnerable to potential complications from CBD products should avoid taking them without discussing them with a medical professional first.
Reduce Risk With Trusted Brands
Follow medical advice from a trusted doctor or qualified professional when you start a CBD oil regimen. If you’ve agreed that CBD is a viable treatment option or that you don’t have risk factors that counter its potential health benefits, you have to make sure you find the right provider that doesn’t include harmful additives in their products.
Whether you’re using edibles, full-spectrum CBD, terpenes, cannabis extract, topicals, hemp oil, or a tincture, make sure you find one with a list of all active ingredients. In case you’re looking for a worst-case scenario, the FDA put out a warning in 2018 that some synthetic cannabinoid products were found to be laced with an anticoagulant called brodifacoum that’s typically found in rat poison.
Since these were described as being sold at gas stations and convenience stores, it’s highly likely they weren’t coming from the most reputable suppliers out there. Do your research and make sure you know exactly what you’re taking before you start taking CBD oil or any similar product. The FDA doesn’t regulate supplements, so shopping around is paramount.
Is CBD Oil An Operation Risk?
Some doctors ask patients to stop taking CBD oil 48 hours or more before a scheduled procedure while others don’t think it’s a serious risk. Doubtless, trained medical professionals know what to look for in individuals so they can make an informed decision about what’s best. It might be comforting to know that, in most cases at least, a history of CBD consumption won’t automatically prevent doctors from getting people the treatment they need.
An example case study from 2017 describes a 44-year old caucasian male who had been having seizures starting when he was 27. The seizures followed a stroke that followed cardiac surgery. The mechanical valve put in place during the cardiac surgery and the nature of his seizures made the 44-year old a bad candidate for surgery, so his doctors opted to refer him to the University of Alabama’s CBD program.
He was taking the blood thinner warfarin in addition to a few other medications to keep his International Normalized Ratio (INR) in line with what was healthy. According to the case study, the patient’s primary care physician slowly lowered his dose of warfarin in tandem with the increase in CBD administered. The final recommendation of the case study is to use INR monitoring when CBD treatment is being administered alongside prescription drugs like warfarin or heparin.
This is a great illustration of an apparently common method of managing the potential risk of CBD’s antiplatelet effects. At the end of the case study, the 44-year old was taking a dose of warfarin that was about 30% lower than when he started and continuing to have CBD administered.
So even if the research about CBDs’ effects on blood thinning and interactions with blood thinners is still far from complete, it’s clear medical professionals are being precautious. It’s best to trust the advice of a trusted medical professional to make sure you’re taking CBD as safely as possible.
Does CBD Oil Lower Your Blood Pressure?
The studies are pretty much across the board on this question. One promising experiment from 2017 indicated that “acute administration of CBD reduces resting blood pressure and the blood pressure increase to stress in humans, associated with an increased heart rate,” which basically means that the 9 participants in the study experienced a drop in their resting blood pressure after a single dose of cannabidiol.
What does that mean for people who have to bring their blood pressure over time, can a regimen of CBD oil accomplish the task? That’s where the research gets a bit less promising. One study from 2020 remarks that CBD “has not affected blood pressure in hypertensive animals.” The same study mentions that most incidents of hypotensive action (low blood pressure) occurred mainly during stress conditions.
Other studies seem to point to some positive results on blood pressure when participants take CBD in moments of stress. However, the evidence either doesn’t support or isn’t conclusive enough to support the idea that CBD is a viable treatment option for lower blood pressure over the long term. You might think that thinner blood automatically creates lower blood pressure, but the two concepts aren’t related.
The beating of your heart creates blood pressure while clotting is meant to stop internal and external bleeding. Adding platelets to the bloodstream doesn’t impact blood pressure. Even when platelets completely block the bloodstream like they do in thrombosis, blood pressure doesn’t change.
But that acute drop in blood pressure could possibly cause problems in certain individuals. If you have problems with your blood pressure being too low in general, it might not be a great idea to consume CBD oil and similar products that source from the hemp plant.
Is CBD Oil Safe?
Ok, so if CBD oil can possibly interact with prescription medications and cause blood to thin and blood pressure to drop following consumption, is it safe to take? Only your doctor can tell you for sure whether it’s a smart treatment option for you. Many have used it to successfully treat epilepsy, anxiety, narcolepsy, and insomnia. By and large, it appears that it is “ a promising candidate of both somatic and psychiatric disorders .”
Many people take CBD oil without any issue. It isn’t psychoactive and there is no indication that it has any addictive qualities. For the majority of people, taking CBD oil from a reputable source where you can see all the active ingredients and none are harmful shouldn’t be a problem.
It’s not as intense as medical marijuana and is available in some places where Mary Jane is not. Many people have used it for pain management or just to relax. People respond differently to these products depending on their individual body chemistry and the context in which they take them.
Some healthcare professionals view CBD oil as a safe alternative to opioids and other prescription treatments for anxiety and sleep disorders. By and large, it is safe. But you should still consult a doctor or another healthcare provider to determine whether you can and are likely to benefit from CBD oil.
Does CBD Oil Thin Blood More Than Other Cannabinoids?
Marijuana as a whole and CBD oil as a part of the whole have both been found to have anticoagulant properties. The best course of action is to avoid hemp-based edible or consumable products if you’re taking heart medication and can’t reach a doctor to get a decision on whether or not CBD oil, edibles, topicals, or even THC products would be dangerous for you to take.
As far as whether CBD oil possesses a blood-thinning capability superior to other extracts from hemp, there’s not much research available on the topic. Out of an abundance of caution, don’t assume that any one product will have less of a blood-thinning effect than another one unless a doctor has told you so.
Despite the indications that CBD oil and other hemp-based products interact badly with blood thinners and could cause your body’s clot-producing ability to fall below where it should be, anecdotal information on the internet seems to indicate that some doctors don’t think it’s a big risk.
Still, an in-person doctor would know best about your health condition and what kinds of factors will have an impact on it. Ask a medical professional before you start taking CBD oil if you’re on blood thinners or at risk for stroke or heart attack. There’s a chance they’ll say it’s fine, but if they say it isn’t you should follow their instructions.
CBD oil has had many positive effects on users’ stress levels and allowed them to sleep more soundly during the night. Doctors have administered CBD oil for epilepsy, narcolepsy, and generalized anxiety disorders. It’s useful for relaxing without the psychoactive characteristics of marijuana or THC.
But marijuana and hemp-derived compounds have been found to interact poorly with blood thinners. For people who take these sorts of prescription medications, anything sourced from the hemp plant could cause some problems.
The danger of taking CBD oil on top of blood thinners is that your blood will become “too thin,” in essence, both of them perform the same function in terms of platelets. So you’d essentially be taking too much of what you need to stay healthy, which can be as disastrous as not staying healthy at all.
Still, the way doctors have balanced CBD administration with steadily decreasing amounts of drugs like warfarin gives some hope that medical professionals will one day know for sure how to organize CBD regimens for people who have had strokes and heart attacks to make sure they can safely take CBD. They’ve already been successful in at least one case study.
For now, users of CBD should check with their doctors to make sure it’s safe for them to start or continue using the product. It’s worth an ask even if you think you’re low-risk. The better prepared and informed you are before you start your CBD regimen, the more beneficial it will be for you in the long run.
CBD and Warfarin: Can You Safely Mix Them Together?
CBD oil is a natural remedy that contains the cannabinoid CBD extracted from the cannabis plant. It’s said to reduce inflammation, provide greater resistance to stress, and promote nerve health.
However, CBD oil may have an adverse drug interaction with anticoagulants such as warfarin.
Can you take CBD oil with warfarin? Read on to find out.
How Does CBD Affect Your Body?
Cannabidiol (CBD) is a compound that comes from the cannabis plant known for its health benefits. CBD oil can be extracted from hemp or marijuana plants. Hemp-based CBD oil is legal in all 50 states, while marijuana-derived CBD oil varies by state.
There are several ways in which CBD affects your body. To begin with, CBD is not addictive and does not cause any withdrawal symptoms. This means taking higher doses of CBD is okay as long as you don’t exceed your daily recommended amount or take too much at once.
Furthermore, CBD is non-psychoactive, meaning it doesn’t get you high, unlike tetrahydrocannabinol (THC), the other compound from the cannabis plant.
These are just some of the common reasons why people use CBD oil:
- Pain relief
- Acne cure
- Weight management
- Brain health
- Cardiovascular health
However, CBD is not for everyone. Some side effects have been reported in rare cases, which may include:
- Dry mouth
- Appetite changes
Additionally, using CBD alongside certain medications raises some questions.
How Does CBD Oil Affect Your Blood?
It has been shown that CBD itself has mild anticoagulating effects, meaning that it can act somewhat like a blood thinner. Nevertheless, more studies must be done to better understand how CBD affects your blood.
In clinical trials, case studies, and scientific research, CBD is shown to work well with the endocannabinoid system in the body.
Following the passage of the Farm Bill, scientists now have greater access to CBD and can finally study its potential as a healing agent. As a result, researchers are conducting more and more studies and clinical trials on CBD every day.
Does CBD Interact With Medications?
Various pharmaceuticals, herbal products, and health supplements can interact with CBD. As a result, the use of other drugs might need to be reduced or modified if CBD is introduced.
The main thing is to understand that some medications should not be taken together.
There are many other factors that can influence drug interactions, such as one’s health condition, the dose of a medication, and the dose of CBD. So if you’re starting a new medication, consult your doctor first before taking CBD oil.
Does CBD Interact With Warfarin?
Short answer: Yes.
Taking any kind of medication or substance requires your body to metabolize it. In the metabolic process, drugs are broken down so the body can absorb their effects.
The chemical structure of a drug determines how it’s broken down by the liver, thereby determining how quickly it leaves your system. The enzyme family called cytochrome P450 (CYP450) is responsible for converting foreign substances and making them easily excreted by the body.
The CYP450 enzyme may be slowed or accelerated by some medication or substance, including CBD.
Drug interactions occur because your body’s metabolism rate is altered during this time. This is referred to as the “grapefruit effect” due to the grapefruit’s ability to slow down the absorption of the drug by the body.
CYP450, CBD Oil, and Warfarin
CYP450 is predominantly responsible for the metabolism of warfarin. CBD inhibits this enzyme class. CBD competes with warfarin on the same metabolic pathway, according to a US National Library of Medicine study published in 2017.
CBD can cause warfarin to stay in the body for too long without being broken down when taken together. This can result in unwanted side effects such as excessive bleeding or overdose.
What Can Increase the Risk of Bleeding?
Warfarin treatment can increase your chances of bleeding during the first three months. The risk is even greater for older adults. You may also be at risk if you use other blood-thinning medications.
Genetic factors may also cause some people who take warfarin to be more prone to bleeding. Your doctor may recommend a genetic test to determine the best dose for you.
Other medical conditions that increase your risk of bleeding are:
- History of stroke
- Kidney problems
- Liver disease
- Ulcers, gastritis, and peptic disease
- Uncontrolled blood pressure
Can You Take CBD Oil With Warfarin?
CBD oil and warfarin should not be taken together. Taking any form of CBD during your warfarin treatment should be avoided as well.
Warfarin is an anticoagulant (blood thinner) medication that prevents the formation of dangerous blood clots that could lead to heart attacks or strokes. Warfarin is available under several brand names, including Coumadin and Jantoven.
Severe bleeding, headaches, swelling, or sudden pain in the extremities are some of the risks associated with warfarin.
A 2017 study published in Epilepsy & Behavior Case Reports showed that CBD increased the effects of blood-thinning drugs like warfarin by slowing down how the body metabolizes the substance. CBD may potentially increase some of the risks of warfarin by extending its duration in the body.
If you’re currently taking warfarin and want to use CBD for another condition, be sure to speak with your healthcare provider first.
Can You Take Other Blood Thinners With CBD Oil?
Drug interactions can be influenced by a number of factors, including your health, weight, and general tolerance. When CBD oil is combined with blood thinners, several considerations must be made.
Two of the remaining three oral anticoagulants approved by the FDA to treat irregular rapid heart rates are also metabolized by the CYP450 system. As a result, they will also be affected by CBD’s grapefruit effect.
Rivaroxaban and apixaban are the oral anticoagulants described.
Further, a study published in 2011 described how dabigatran (Pradaxa), another oral anticoagulant, doesn’t undergo CYP450 metabolism. A review of dabigatran suggests that the drug may have a few drug-food and drug-drug interactions. The use of dabigatran as an alternative to warfarin treatment is also being considered.
Once again, it’s advisable to consult your doctor before taking any anticoagulant together with CBD to determine safety and tolerance.
The FDA has authorized warfarin use for the following purposes:
- Treatment of venous thrombosis, associated pulmonary embolisms, and pulmonary thrombosis.
- Treatment of thromboembolic complications caused by cardiac valve replacement or irregular or rapid heartbeats (atrial fibrillation).
- Identify and prevent deaths, recurrent heart attacks or myocardial infarctions (MI), and other thromboembolic events like strokes and systemic embolisms that may follow a cardiac arrest.
Can CBD Replace Warfarin?
The overall research on CBD is relatively young compared to traditional drugs. Currently, CBD has not been explicitly evaluated as a safe replacement for warfarin or any form of the anticoagulant.
Phytomedicine published a study written in 2007 that used an obese rat model to show that cannabis extracts may have anticoagulant effects. In this study, cannabinoids like cannabinol (CBN) and tetrahydrocannabinol (THC) exhibited anticoagulant properties.
According to the researchers, the cannabinoids THC and CBN from Cannabis sativa were possible treatments for thrombosis and diabetes, a condition that could lead to an irregular rise in blood clotting.
There have been limited studies to determine if CBD can act as an anticoagulant, and at this time, there is no evidence that CBD can act as an anticoagulant medication.
You should still consult a medical expert before taking CBD as a substitute for warfarin or any prescription medication. There are still many unknowns regarding CBD’s effects on the body.
What To Look For When Shopping for CBD Oil
The market for CBD oil has expanded a lot in recent years. It is available online and in stores across the country. However, not all CBD oils are created equal and there are certain things you should know before purchasing your first bottle.
Some people are not sure what CBD concentration means when buying CBD oil.
There are many different types, and some can be much stronger than others. The concentration will depend on what you’re looking to use the CBD oil for and how often you plan on using it. The higher the concentration, the stronger the effects are likely to be.
There is also a limit to the amount of THC that can be present in a product. The percentage of THC in CBD oil should be clear on its label.
The next thing you should look at is how much CBD is in each dosage (the number of milligrams). Taking a certain amount of CBD will vary depending on the concentration as well as other factors like age or medical needs.
CBD Vendor’s Certificate of Analysis (COA)
Before buying CBD oil, it’s important to check its COA. This will not only ensure that the product is of good quality but also tell you if the vendor has been trustworthy in providing accurate information about the product.
This certificate ensures that the product is safe, and you shouldn’t have any worries about what you’re putting into your body. It lets you know that this product has been tested and meets all safety standards mandated by law.
When shopping for CBD oil, check the CBD’s source. If you’re in the United States, it’s best to buy CBD that uses American-grown organic hemp.
Hemp is a bioaccumulator, which means it absorbs the nutrients and elements from the soil it’s planted. These nutrients are dissolved within the plant’s cell walls and then released throughout its life cycle.
Bioaccumulators are effective at absorbing either good or harmful elements. So you can also compromise the quality of the CBD plant if polluted soil is used.
Ideally, hemp should be grown in fertile soil with no harsh chemicals.
CBD products may be formulated with beneficial ingredients like MCT oils or melatonin.
Unfortunately, CBD products can sometimes contain potentially hazardous ingredients, such as vegetable glycerin and propylene. So be aware of these substances and steer clear of CBD products containing them.
Other Products That May Interact With Warfarin
In addition to individual factors, there are several drug interactions that can change how your body reacts.
Warfarin interacts with vitamins, nutritional supplements, drugs, and food. These items may reduce the efficacy of warfarin or increase bleeding risks.
Here’s a list of common foods and drinks to avoid while taking warfarin:
- Grapefruit or grapefruit juice
- Cranberries or cranberry juice
- Pomegranate or pomegranate juice
- Black licorice
Here’s a list of common drugs to avoid while taking warfarin:
- Abnormal heart rhythm medications, such as amiodarone (Pacerone, Nexterone)
- Aspirin or products containing aspirin
- Antacids or laxatives
- Antifungal medications, including fluconazole (Diflucan)
- Colds and allergy medications
- Ibuprofen (Advil, Motrin IB, etc.)
- Naproxen sodium (Aleve, Naprelan, etc.)
- Product containing acetaminophen (Tylenol, etc.)
Here’s a list of common herbal or nutritional supplements to avoid while taking warfarin:
- Vitamin E
- Green tea
- Dong quai (Angelica sinensis)
- St. John’s wort
- Coenzyme Q10 (ubiquinone)
Key Takeaways on Interactions Between CBD and Warfarin
The body absorbs CBD through the CPY450 system, which also helps your body process warfarin. Therefore, combining CBD with warfarin is not advisable.
If you insist on taking CBD together with it, warfarin may stay in your body for longer than necessary. This can lead to severe side effects such as excessive bleeding and even death from overdose.
If you’re on warfarin or about to use this medicine, be mindful of the other foods, drugs, and supplements that you should avoid as well.
CBD oil is a legal and safe drug in the United States. However, there are laws different for every state and you should make sure we check the law first before you buy CBD oil.
There are many benefits of using CBD. However, there are many fake products out there that don’t meet quality standards. To maximize its benefits and prevent any harm to your body, be sure to buy from a trusted source. You should also make sure that the product has been third-party tested.
Most importantly, it’s highly recommended to seek medical advice before using CBD products as a replacement for a prescribed drug or a nutritional supplement.
Have you tried taking CBD and warfarin together? Share your experience in the comments below to help other readers!
- Grinspoon, P. (2019, Aug 27). Cannabidiol (CBD) — what we know and what we don’t. Retrieved from https://www.health.harvard.edu/blog/cannabidiol-cbd-what-we-know-and-what-we-dont-2018082414476. (1)
- Yamaori S., Koeda K., Kushihara M., Hada Y., Yamamoto I., Watanabe K. Comparison in the in vitro inhibitory effects of major phytocannabinoids and polycyclic aromatic hydrocarbons contained in marijuana smoke on cytochrome P450 2C9 activity. Drug Metab Pharmacokinet. 2012;27(3):294–300. (2)
- Deaton, J. G., & Nappe, T. M. (n.d.). Warfarin Toxicity. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK431112/
- Doliner B, Jaller JA, Lopez AJ, Lev-Tov H. Treatments to prevent primary venous ulceration after deep venous thrombosis. J Vasc Surg Venous Lymphat Disord. 2019 Mar;7(2):260-271.e1.
- W., M., D., K., & M., B. (2013). Co-administration of rivaroxaban with drugs that share its elimination pathways: pharmacokinetic effects in healthy subjects. doi: 10.1111/bcp.12075.
- Ganetsky, M., Babu, K. M., Salhanick, S. D., Brown, R. S., & Boyer, E. W. (2011). Dabigatran: Review of Pharmacology and Management of Bleeding Complications of This Novel Oral Anticoagulant, 7(4). doi: 10.1007/s13181-011-0178-y
- Sharp CR, deLaforcade AM, Koenigshof AM, Lynch AM, Thomason JM. Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE): Domain 4-Refining and monitoring antithrombotic therapies. J Vet Emerg Crit Care (San Antonio). 2019 Jan;29(1):75-87.
- Badjatiya A, Rao SV. Advances in Antiplatelet and Anticoagulant Therapies for NSTE-ACS. Curr Cardiol Rep. 2019 Jan 12;21(1):3.
- Unger, E. F. (2015, October 16). Atrial fibrillation and new oral anticoagulant drugs. Retrieved from https://www.fda.gov/drugs/news-events-human-drugs/atrial-fibrillation-and-new-oral-anticoagulant-drugs
- Coetzee, C., Levendal, R. A., van de Venter, M., & Frost, C. L. (2007). Anticoagulant effects of a Cannabis extract in an obese rat model. Phytomedicine, 14(5). doi: 10.1016/j.phymed.2006.02.004
Nina created CFAH.org following the birth of her second child. She was a science and math teacher for 6 years prior to becoming a parent — teaching in schools in White Plains, New York and later in Paterson, New Jersey.
Is cannabis a blood thinner?
Ever wondered how cannabinoids like THC or CBD affect your blood? It may seem like a weird question, but it is a vitally important one for anyone taking anticoagulant medications and considering using cannabis. It turns out that this issue has been under-researched and could have significant impacts on patients who may be at greater risk of heart attacks and strokes.
What is a blood thinner?
It is not uncommon for patients at a high risk of blood clots and strokes to receive medications called “anticoagulants” or “antiplatelet drugs”, often generically referred to as “blood thinners.” These drugs do exactly what you might expect – prevent blood from forming a clot. It is important to note that while clotting is good and necessary when you have a cut or injury, forming a clot inappropriately can be highly dangerous. Blood clots can greatly interrupt blood flow to the surrounding tissue, causing serious damage to important organs, and sometimes death. Some common examples of anticoagulant blood thinning medications on the market include warfarin (Coumadin), heparin, apixaban (Eliquis), and enoxaparin (Lovenox). One of the most common examples of an antiplatelet drug is aspirin.
How do blood thinners work?
Blood thinners typically act in one of two ways – as anticoagulants or antiplatelets. But before we explain how these drugs work, it is important to understand a couple of things about blood clotting in the human body.
Blood consists of several primary constituents including plasma, red blood cells, white blood cells, and platelets. Whenever we injure ourselves and break a blood vessel, causing bleeding, platelets start to attach to the damaged tissue and act as a kind of cork that plugs the hole in the blood vessel. 1
Blood thinners disrupt the blood clotting process in one of two ways. Anticoagulants typically slow down the process of blood clotting by interrupting clotting factors, whereas antiplatelet drugs prevent platelets from coming together to form blood clots in the first place.
Typically, “blood thinners” refer to anticoagulants, though you may find the term “blood thinner” applied to either anticoagulants or antiplatelet drugs.
Does weed thin your blood?
The short answer is – no, in most cases cannabinoids do not seem to act as strong blood thinners. There are very few case studies that report anticoagulant effects in cannabis patients, and the ones that do exist involve using cannabis with traditional anticoagulant medications. 2
While the general concensus is that phytocannabinoids (derived from the cannabis plant) do not cause anticoagulations, there has been only one study that found that THC, CBD and CBN could thin the blood of obese rodents. Preclinical rodent studies are challenging to interpret, however, as the results very often don’t directly scale to the human biological system. In this study the authors speculated that cannabinoids may be inhibiting an enzyme in blood plasma called thrombin, which promotes blood clotting. Additionally, the authors noted that THC (and CBD for that matter) are known to interact with receptors known as PPARy 3 , which are highly present in blood vessels. Lastly the authors note that certain endocannabinoids like anandamide may promote clotting, but these tests were in vitro (aka in a laboratory test-tube), not in a living animal. 4
There have also been reports that synthetic cannabinoids, aka spice or K2, may cause blood thinning due to contaminants found mixed with the cannabinoids. Basically, rat poison designed to work by making rodents bleed to death is occasionally mixed with synthetic cannabinoids, either accidentally or as a cutting agent, which can cause coagulopathy (aka inappropriate clotting). In this case, hundreds of patients were seen in emergency departments in 2018 with signs of bleeding with no known cause. It was later found that many of these patients had been consuming synthetic cannabinoid products, and these products were contaminated with rat poison. This is yet another cautionary tale regarding synthetic cannabinoids and another reason why cannabis regulations allowing for safe access to cannabis are so important. 5 6
Is it safe to use THC with blood thinners?
This is a tricky one given the lack of research. In general patients taking anticoagulants often have cardiovascular issues, which can be problematic with cannabis use as THC is known to cause changes in heart rate and blood pressure. This effect is particularly strong with smoking or vaping THC products, but can also happen with edibles. So it follows that THC should likely be avoided if a patient is taking blood thinners.
If a patient is taking anticoagulants, that could indicate that their cardiovascular system may not be in the best of health to begin with. This can be problematic with cannabis use, in particular THC which is known to cause changes in heart rate and blood pressure. Generally, patients with high risks of strokes, heart attacks and other cardiovascular dysfunction are those most commonly prescribed blood thinners. Since THC carries its own risk of exacerbating cardiovascular issues in susceptible users and should likely be avoided if a patient is taking blood thinners. 7
As far as THC’s anticoagulant effects are concerned, there is very limited evidence that THC may act as an anticoagulant by inhibiting thrombin, but that evidence is in rodents and stems from only one study mentioned previously. The real concern about THC in this population is actually related to blood pressure, heart rate and heart rhythm; an older heart may be even more susceptible to these changes. 8 9
CBD and Blood Thinners
As mentioned previously, CBD is a known PPARy receptor agonist, causing vasorelaxation and lowering blood pressure. CBD is also known to interfere with the normal function of certain enzymes already inside of us, known as cytochrome P450 enzymes. These CYP450 enzymes are all over our bodies and play important roles in metabolizing food and drugs. Cannabidiol is a known inhibitor of some CYP enzymes, leading to an increased risk of pharmaceutical drug interactions. And CBD is not alone in this effect. Many other phytocannabinoids do carry this potential to interfere with liver enzymes – though all of them do so with lesser potency than CBD. In simple terms, CBD can slow the body’s ability to break down common medications – including blood thinners.
There are multiple case reports available which detail situations in which patients have experienced herb-drug or drug-drug interactions between CBD and a common anticoagulant, warfarin (Coumadin). In one instance, a 46-year-old male patient required a nearly 20% reduction in their warfarin dose after beginning Epidiolex, a pharmaceutical containing CBD isolate in a liquid solution. In another instance, a 44 year-old male patient required a 30% dose reduction in warfarin after starting to use CBD oil. There was, however, one case report where this drug interaction did not occur. 10 11 12 13 14
These drug interactions highlight some important lessons. First, it is important to recognize that pharmaceutical interactions with cannabis are very real and can be dangerous if not monitored properly – especially in the context of drugs like blood thinners. However, there is a flip side to this drug interaction issue. Oftentimes, if a patient and their physician are aware of these potential interactions, it’s possible a patient could choose to continue using anticoagulants and cannabis together. This combination would likely warrant close monitoring of the anticoagulant effects, and would certainly require increased communication between the patient and the medical provider. But if monitored properly, it’s possible that the dose of patient’s anticoagulants could be reduced, possibly reducing the risk of serious negative side effects from those medications while still deriving benefit from the cannabinoids.
Bottom line: Talk to your healthcare provider
So what does all of this mean? Is marijuana a blood thinner?
According to the miniscule amount of research that has been performed so far on this topic, it is possible that cannabinoids like THC or CBD could act as anticoagulants, and the endocannabinoid system is involved in platelet aggregation. However, it appears this effect may only be in certain contexts, for instance, in the rodent study that identified anticoagulant effects of THC, CBD and CBN, the rodents were obese rodents in a simulated Type-2 diabetes model. In that scenario, cannabinoids exhibited anticoagulant effects by inhibiting the blood clotting signaling compound thrombin. However, we do not know how that would scale up to humans with Type 2 diabetes or other conditions. 15
We do know that cannabinoids can interact negatively with blood thinning medications, either by inhibiting their breakdown and elevating their concentrations in the body or by preventing their activation. In both cases, this can be extremely dangerous for patients, as coagulation of blood is a fine balance of clotting and bleeding, and the result of managing these medications poorly can be as serious as death. This is why it is so important to talk to a healthcare professional if you plan to try using cannabis in combination with anticoagulant and antiplatelet medications. Your physician can arrange regular blood tests to monitor for interactions with other medications and take appropriate steps as needed to keep you safe.
So for now, the jury is still out. There is a tiny bit of preclinical evidence that cannabinoids may affect blood’s ability to clot, but a lot more research is still needed. However if you combine cannabis products, especially CBD, with your anticoagulant or antiplatelet medication, be sure to take extra caution to monitor the effects with your doctor.