Can I Use Marijuana If I’m Taking Blood Thinners?

Can I Use Marijuana If I'm Taking Blood Thinners

Coumadin and Cannabis: What Happens When You Mix Warfarin & Weed?

Coumadin, or warfarin, is a kind of anti-coagulant. It prevents the blood from coagulating, or clotting.

Cannabis can also act as an anticoagulant, so patients often wonder, can I use marijuana if I’m taking blood thinners?

Usually, yes, but caution should be exercised. 

Most patients taking blood thinners can use cannabis without ill effects. However, these patients should use caution and consume marijuana under the guidance of an experienced healthcare provider.

Here are some of the things to know about mixing weed and blood thinners like warfarin or coumadin.

mixing weed with blood thinners

Mixing Medical Marijuana & Blood Thinners: The Facts

A 2007 study published in Phytomedicine showed cannabis, especially cannabinoids THC and CBN, act and anti-coagulants. The same study showed CBD had mild anti-coagulating effects.

Additionally, some blood thinners, like Coumadin, or warfarin, utilize metabolic pathway CYP450. Cannabis utilizes the pathway. In some patients, this can cause a drug interaction and increase the amount of medication in the blood.

Don’t freak out at the mention of drug interactions. Drugs that utilize CYP450 can interact with a variety of things, even menthol cough drops are suspected of interacting with blood thinners.

(Read More About Cannabis & Medication Interactions)

Becuase cannabis is an anti-coagulant and because of the potential for blood thinners and cannabis to interact, patients on blood thinners should use caution when adding medical marijuana to their routine.

Coumadin and Cannabis: What Happen When You Mix Warfarin & Weed
Coumadin and Cannabis: What Happen When You Mix Warfarin & Weed?

Cannabis With Blood Thinners: Watch For This

Healthcare providers should monitor platelet levels and coagulation factors (PTT, PT/INR, CBC), especially during the first few months of adding medical marijuana.

Patients who mix weed and blood thinners (and/or their caregivers) should also be aware of the signs of “thin blood”.

Coumadin and Cannabis: What Happen When You Mix Warfarin & Weed?

What Is Thin Blood

“Thin blood” means the blood does not clot adequately. In severe cases “thin blood” can be deadly.

Signs or symptoms your blood might be too thin.

  • Bleeding Gums
  • Nosebleeds
  • Bruising
  • Petechiae
  • Blood in urine or stool
  • Heavy menstrual bleeding
  • Unusual bleeding from small cuts
  • Slow wound healing

Patients Should Know

There have been case studies attributing excess bleeding to a cannabis and coumadin interaction, however, many patients taking blood thinners use recreational cannabis without issue.  Caution should be utilized.


Can Patients on Blood Thinners Use Cannabis Occasionally?

Patients should know that adding an occasional high dose of cannabis can cause blood to thin temporarily.

This could be as dangerous as taking a one-time double dose of blood-thinner medication, it temporarily increases the risks but is unlikely to cause long-term issues. As the cannabinoids are excreted from the body, the platelets and clotting factors should return to their previous levels.

Medical marijuana reciprocity laws


According to anecdotal evidence, many patients taking blood thinners use medical marijuana effectively without reporting significant interactions, however, all patients with cardiac issues should use cannabis under the guidance of their doctors.

When patients taking blood thinners choose to use marijuana,  they should know the signs and symptoms of thin blood, and consume cannabis under the care of a licensed healthcare provider.

Written by Jessie Gill

Jessie Gill, RN is a cannabis nurse with a background in holistic health and hospice. After suffering a spinal injury, she reluctantly became a medical marijuana patient then quickly transitioned into an advocate. Her site, combines science with personal insight to educate about medical marijuana. She’s been featured on Viceland and bylines include GoodHousekeeping, Cosmopolitan, MSN, and more.

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