Cannabis (THC-Dominant) and Warfarin: what the published research says
PubMed indexes 8 records that name Cannabis (THC-Dominant) and Warfarin together, either in the title or in an interaction, co-administration, or pharmacokinetic context. Each one is listed below with its study design and, where the abstract states one, the authors’ own conclusion, quoted and linked. This page reports that literature. It does not tell you whether to combine them.
Every statement below is attributed to a named, dated, linked source.
This page lists published research relevant to Cannabis (THC-Dominant) and Warfarin. It deliberately does not state whether the combination is safe, whether it interacts, in which direction, at what dose, or how far apart to take them.
A study appearing here is not proof that an interaction exists. Two substances can be named together in a paper that never tested them in combination, and a source listed as background may cover only one of them.
Findings are quoted from each abstract as the authors wrote them. NutriStack has not re-analysed, pooled, or reconciled them, and they may disagree with each other.
NutriStack’s own interaction assessment for this pair is not published here. It has not completed qualified-human clinical review, so it is withheld from search. See the publication gate.
Nothing here is medical advice. Decisions about prescription medication and supplements belong with your prescriber or pharmacist, who can see your full regimen.
The research
8 studies naming Cannabis (THC-Dominant) and Warfarin.
Strongest relevance first: papers naming both substances in the title, then human trials and systematic reviews.
“Following the cessation of cannabis use, the INR levels decreased and returned to the therapeutic range for warfarin therapy. In summary, the current report indicates that water-boiled cannabis may influence the outcomes of warfarin therapy, as evidenced by the changes in INR levels.”
Names both Cannabis (THC-Dominant) and Warfarin in its title.
Journal of pharmacy practice · 2020 · PMID 31319733
Case ReportsHuman subjects
“There are no previous reports of interactions between edible cannabis and warfarin, with very few case reports describing the interaction with other forms of cannabis. Close monitoring of INR in patients with concomitant cannabis is recommended for proper warfarin management.”
Names both Cannabis (THC-Dominant) and Warfarin in its title.
“The available, although sparse, data suggest that use of cannabinoids increases INR values in patients receiving warfarin. Until further data are available, we suggest patients receiving warfarin be warned against cannabis use.”
Names both Cannabis (THC-Dominant) and Warfarin in its title.
The Annals of pharmacotherapy · 2009 · PMID 19531696
Case ReportsHuman subjects
“To our knowledge, there have been no other reported cases of warfarin-marijuana interaction. While more clinical reports would be useful to confirm this interaction, clinicians should be aware of its probability so as to manage patients appropriately.”
Names both Cannabis (THC-Dominant) and Warfarin in its title.
Journal of cannabis research · 2022 · PMID 35012687
“Despite the introduction and use of medical cannabis therapy, with both THC and CBD components, an elderly patient with concurrent warfarin use did not see major INR fluctuations, in contrast to published literature. The potential for warfarin and THC/CBD interactions may be dependent on route of administration and dose of the cannabis product.”
Names both Cannabis (THC-Dominant) and Warfarin in its title.
“Drug-drug interactions with cannabinoids are likely amongst prescription medications that use common CYP450 systems. Our findings highlight the need for healthcare providers and patients/care-givers to openly communicate about cannabis/cannabinoid use to prevent unintended adverse events. To that end, we have developed a free online tool (www.CANN-DIR.psu.edu) to help identify potential cannabinoid drug-drug interactions with prescription medications.”
Names Cannabis (THC-Dominant) and Warfarin together in an interaction, co-administration, or pharmacokinetic context.
Clinical and translational science · 2024 · PMID 38720531
Systematic ReviewHuman subjects
“In addition, dose titrations or treatment withdrawal could help mitigate the adverse effects attributed to cannabis-drug interactions. Nevertheless, novel drugs are constantly emerging, and more research is needed to further identify potential interactions with cannabis.”
Names Cannabis (THC-Dominant) and Warfarin together in an interaction, co-administration, or pharmacokinetic context.
“Clinician recognition of this potential interaction is important. Available evidence supports the need to conduct a drug interaction study between cannabinoids and warfarin to clarify the existence of an interaction.”
Names Cannabis (THC-Dominant) and Warfarin together in an interaction, co-administration, or pharmacokinetic context.
Limitations
What this evidence cannot tell you.
Search-based evidence indexes have real limits, and it is worth being explicit about them:
Selection. These records were found by searching PubMed titles and abstracts for both substance names alongside interaction and pharmacokinetic terms. Relevant work that phrases things differently, or is not indexed in PubMed, will be missing.
No effect size. The quoted conclusions are the authors’ words about their own study. We have not extracted effect direction or magnitude, and a single study’s conclusion is not a consensus.
Population mismatch. Findings in healthy volunteers, animals, or a specific patient group may not transfer to you, your dose, or your formulation.
Absence is not safety. Few published studies means the combination is under-studied, which is not the same as established as safe.
Nearby evidence
Other pairs with published research.
Pages covering Cannabis (THC-Dominant) or Warfarin alongside a different substance.
NutriStack is a free iPhone app for organising a supplement routine: what you take, when, and what the published record says about it. Its exploratory interaction checker covers Cannabis (THC-Dominant), Warfarin, and several hundred other substances.
The checker is a research and organisation tool, not a clinical decision aid, and its per-pair assessments are excluded from search until they pass claim-level review.
NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.
