Does CBD oil thin your blood?

by Apoorva Shivankar, M.D

Does CBD oil thin your blood?

Is CBD a Blood Thinner?

With the rapid globalization of Cannabidiol (CBD) and its grand acceptance by the people worldwide, it becomes equally important to keep an eye on the darker side of this highly influential drug too.

Yes, CBD does have its share of side effects. One such point of concern making headlines recently is the blood-thinning side effect of CBD, which can make even a religious follower of CBD think twice before taking the next jab, forget about those suffering from blood pressure issues, coagulation disorders, bleeding tendencies, stroke, haemorrhage or those taking regular blood thinners.

What is blood-thinning?

Blood-thinning has nothing to do with the viscosity of blood. It is actually the measure of blood’s ability to form clots. Increased thinning indicates lower coagulation potential which results in increased blood flow. It has its own set of benefits and drawbacks. But first, let’s see how clotting occurs normally.

Blood Clotting

The complicated coagulation mechanism can be summarized in 4 critical steps:

  1. Injury causing damage to blood vessel followed by constriction of the same.
  2. Platelets from the circulatory system go and get adhered to the damaged vessel wall forming a temporary plug to stop bleeding.
  3. In the meanwhile, the coagulation cascade comprising of 13 clotting factors gets activated
  4. This activated coagulation cascade generates a fibrin mesh to reinforce the platelet plug forming a clot.

Any deviation in this pathway leads to failure of coagulation also known as blood-thinning.

A word about existing blood thinners

Yes, blood can be thinned out using medications. Though coagulation of blood is an important natural phenomenon to prevent blood loss, there are certain hypercoagulable states (protein C or S deficiency, cardiac defects, coagulation disorders, antiphospholipid syndrome, etc.) wherein the body starts forming clots within and these can be fatally dangerous as they block the blood flow to the heart, brain, lungs and other vital organs.

These people face an increased risk of DVT, stroke, pulmonary embolisms, and even infarctions. Here comes the role of blood thinner which can delay and even prevent new clot formation, deter the growth of existing clots, maintain smooth blood flow and can potentially save life.

These thinning drugs come in 2 categories

  • Anticoagulants

    Anticoagulants interfere with the clotting factors hindering the normal coagulation process. The most common anticoagulant warfarin is a Vitamin K antagonist. It depletes vitamin k which is a must for activating the cascade factors. Heparin on the other hand directly alters the functioning of thrombin and fibrin, the 2 vital cofactors of the coagulation cascade.

    Other similar prescription drugs include Enoxaparin, Rivaroxaban, Apixaban, Dabigatran.

    • Antiplatelets

      Antiplatelets work by limiting the ability of platelets to clump together and adhere to the vessel walls preventing clot formation.

      Ex.  Aspirin, Clopidogrel, Dipyridamole, Prasugrel. 

      Coming to the main question:

      Does CBD oil affect blood work?

      Cannabidiol has shown 2 major impacts on the circulatory system of the body:

      • It can lower blood pressure.
        - By reducing inflammation and allowing the blood vessels to relax. 
      • Can act as a blood thinner.
        -By a mechanism similar to the grapefruit juice effect.

      CBD oil as a blood thinner in detail

      This thinning power of CBD oil is a result of it’s

      1. Interactions with other blood thinners
      2. Its own biochemical profile

      Interactions with other blood thinners

      • CBD uses CYP450 family of liver enzymes to undergo its own metabolism. This CYP450 system includes the major metabolic enzymes (CYP3A4, CYP2C9, CYP2D6, CYP2C19, etc.) which are involved in the breakdown of toxins and around 60% of all medications including the blood thinners consumed.

        So, if taken along with thinners, CBD uses up and thus, competitively inhibits almost all enzymes of CYP450 system. This leaves very little CYP450 available for processing the anticoagulants especially coumadin (warfarin- CYP3A4, CYP2C9), the most commonly prescribed anticoagulant drug.

        As a result, higher amounts of anticoagulants enter the blood and stay for a longer duration in the body increasing the risk of bleeding tendencies. This action mimics the well-known effect of grapefruit juice which states that “the juice lets more of the drug enter the blood by blocking CYP3A4.”

      • CBD oil is also known to suppress the production of platelets and some of the clotting factors.

      • By inhibiting CYP450, CBD oil by default inhibits CYP2C19 an enzyme essential for converting the antiplatelet agent Clopidogrel into its active metabolite thiol. This impedes platelet plug formation and ultimately adds to the thinning ability of CBD oil.

      Its own biochemical profile

      Apart from altering the actions of anticoagulant and antiplatelet prescription drugs, CBD has a blood-thinning action of its own too. Research 4 conducted on rodent models in the year 2006 showed that the clotting time was almost doubled in rats treated with cannabis plant extract as compared to controls.

      They further stated that the cannabinoids-CBD, THC and CBN-content in cannabis extract are responsible for the anticoagulation effects of CBD. These results stress on the possibility that full-spectrum CBD products containing terpenes, CBD, THC and CBN can manifest a significant coagulation inhibitory effect.

      Also, similar but less impactful effects can be seen with broad-spectrum and CBD isolate products. The research also stated that the anticoagulatory effects of CBD are more prominent than its cousin cannabinoids.

      Combining CBD oil and Blood thinners. Is it safe?

      The unending list of CBD oil health benefits is tempting people one and all and those taking thinners are not an exception. They too get attracted/drawn towards CBD products for some reasons or the other. But then there is a risk.

      Blood-thinning drugs like warfarin or clopidogrel are often prescribed to individuals with a history of myocardial infarction, stroke, surgical procedure, or those with increased risk of any of these.

      Moreover, the post-surgical patients with cardiac stents are prescribed clopidogrel to block the platelets from activating and clogging up the arteries. These blood- thinning medications act as life saviours in such situations by preventing vascular blockage.

      If these patients start using CBD products in addition to their routine medications, the CBD oil will increase the bioavailability of anticoagulants and limit the antiplatelet action imparting an additive thinning effect. This additive action rather than improving the status can be more dangerous by precipitating uncontrolled bleeding issues like internal haemorrhages, bleeds around your heart, in your eye, brain, abdomen or spine.

      Other possible undesirable effects of CBD in patients on blood thinners include:

      • Brown or red urine
      • Unusual and frequent bruising
      • Black or bloody stools
      • Nosebleeds
      • Chronic stomach pain
      • Headache
      • Unusual tiredness, weakness, or dizziness
      • Lowered blood pressure
      • Joint pain and discomfort, especially in case of injury.

      All this happens due to an overdose of anticoagulation owing to the slower metabolism induced by CBD oil and demands immediate medical attention.

      What are the safer options to use CBD oil and thinners together?

      • Actually, it is not advisable to use CBD oil and thinners together. But if it is really necessary, it should be strictly under the guidance of your doctor.
      • If such cases, blood thinners like Dabigatran, Edoxaban, Betrixaban or natural heparin serve as a good option as they show minimal CYP metabolism. Though theoretically, CBD does not interact with these thinners, there is still no direct evidence to validate their use. Caution and medical vigilance are always the keys.
      • Always consult with a doctor to find out the form and type of CBD product to be used with your daily medications in order to minimize adverse interactions.
      • Start low and go slow. Yes, if you are adding CBD oil to your medication regime begin with the lowest possible dose and slowly work your way up to prevent any drug interaction on a big scale.
      • Prefer high-quality CBD product brands that have been organically grown, sustainably sourced, and third-party lab tested.
      • Always keep in mind that the additional chemicals in CBD oil can also interact with your body or other medications in unexpected ways.

      Can CBD oil replace the prescribed Blood Thinners?

      Though CBD possesses its own anticoagulant action, this effect is neither well studied nor at par with that of existing thinners. Plus, CBD use is not Food and Drug Administration approved and there are no strict regulations for its cultivation, extraction, purification, formulation, etc giving room for malpractices. Hence, CBD cannot be termed as a full-blown blood thinner individually.

      What are the side effects of CBD oil?

      Rare but can be seen with higher doses

      • Nausea and general sickness.
      • Loss of appetite and dry mouth.
      • Drowsiness and light-headedness.
      • Lowers blood pressure.
      • Worsening of Parkinson's disease. 

      To sum up

      Blood-thinning drugs are like a double-edged sword. When used in correct doses, they are life-saving for conditions like heart or blood vessel disease, an irregular heart rhythm, systemic lupus, or deep vein thrombosis whereas the same drugs when used in higher concentration can cause severe internal bleeding.

      So, a perfect balance has to be maintained while using thinners. CBD with its unique ability to increase the effectiveness of thinners along with the possibility of adding on its own anticoagulation powers can easily disturb this balance causing excessive bleeding Hence, though safe when used alone, its use along with other thinners should be strictly under physician observation.


      Q. Does CBD oil help clogged arteries?

      CBD oil will not dissolve the clot on its own but it can help by dilating and relaxing the vessel walls.

      Q. Is There A Difference Between Topical & Oral forms of CBD?

      CBD used as topical creams do not compete with blood-thinning drugs for CYP450 unlike the oral CBD product use and hence will not increase the blood flow and bleeding tendencies.

      Q. Any precautions for CBD use before surgical procedure?

      Some doctors believe it’s best to discontinue the use of CBD up to 48 hours before undergoing the procedure. Others claim that there should be no issue consuming CBD before the procedure unless the patient is also on blood-thinning medications like warfarin.

      Q. Can CBD products alone (in the absence of thinners) cause bleeding issue?

      Even though CBD has an anticoagulation action of itself, this effect is very mild and till now there is no clinical evidence showing increased blood loss with the solo use of any CBD product.


      1. Mega JL, Close SL, Wiviott SD, Shen L, Hockett RD, Brandt JT, Walker JR, Antman EM, Macias W, Braunwald E, Sabatine MS. Cytochrome p-450 polymorphisms and response to clopidogrel. N Engl J Med. 2009 Jan 22;360(4):354-62. doi: 10.1056/NEJMoa0809171. Epub 2008 Dec 22. PMID: 19106084.
      2. Simon T, Verstuyft C, Mary-Krause M, et al. Genetic determinants of response to clopidogrel and cardiovascular events. The New England Journal of Medicine. 2009 Jan;360(4):363-375. DOI: 10.1056/nejmoa0808227.
      3. Dean L. Clopidogrel Therapy and CYP2C19 Genotype. 2012 Mar 8 [Updated 2018 Apr 18]. In: Pratt VM, Scott SA, Pirmohamed M, et al., editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012-. Available from:
      4. Coetzee, C & Levendal, R-A & Van de Venter, Maryna & Frost, Carminita. (2007). Anticoagulant effects of a Cannabis extract in an obese rat model. Phytomedicine : international journal of phytotherapy and phytopharmacology. 14. 333-7. 10.1016/j.phymed.2006.02.004.
      5. Jadoon KA, Tan GD, O'Sullivan SE. A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study. JCI Insight. 2017 Jun 15;2(12):e93760. doi: 10.1172/jci.insight.93760. PMID: 28614793; PMCID: PMC5470879.
      6. Franz CA, Frishman WH. Marijuana Use and Cardiovascular Disease. Cardiol Rev. 2016 Jul-Aug;24(4):158-62. doi: 10.1097/CRD.0000000000000103. PMID: 26886465.
      7. Ganetsky M, Babu KM, Salhanick SD, Brown RS, Boyer EW. Dabigatran: review of pharmacology and management of bleeding complications of this novel oral anticoagulant. J Med Toxicol. 2011 Dec;7(4):281-7. doi: 10.1007/s13181-011-0178-y. PMID: 21887485; PMCID: PMC3550194.

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