What happens when you take broccoli with warfarin?
Warfarin works by blocking the recycling of vitamin K in the liver, which is required to activate clotting factors II, VII, IX and X. Broccoli is one of the most vitamin K-dense common vegetables, containing roughly 100 to 200 micrograms of vitamin K1 (phylloquinone) per 100 grams of cooked florets. When you eat a large serving of broccoli, you flood your liver with the very cofactor warfarin is trying to block, which can blunt the drug's anticoagulant effect and push your INR down.
The interaction is dose-related and depends much more on change than on absolute intake. A patient who eats broccoli twice a week, every week, will reach a stable INR on a stable warfarin dose. The trouble starts when intake swings: a sudden weeklong broccoli kick after months of avoiding greens can drop the INR into the subtherapeutic range, while abruptly cutting out a long-standing serving of broccoli can push the INR up into the bleeding zone.
Why is this important?
An INR that drifts below the therapeutic range (usually 2.0 to 3.0 for most indications) leaves the patient unprotected from the clot they were prescribed warfarin to prevent, whether that is stroke from atrial fibrillation, deep vein thrombosis, pulmonary embolism, or a mechanical heart valve thrombus. Conversely, an INR that drifts too high raises the risk of serious bleeding, including intracranial hemorrhage.
Historically, clinicians told warfarin patients to avoid green leafy vegetables entirely. Modern anticoagulation guidance, summarized in a 2016 systematic review on dietary vitamin K and vitamin K antagonists, has reversed that advice. Very low and fluctuating vitamin K intake is associated with worse INR control than steady moderate intake, because the warfarin dose can be titrated against a predictable dietary baseline. Eliminating broccoli from a previously broccoli-heavy diet is itself a clinically meaningful change that can destabilize anticoagulation.
What should you do?
Keep your intake of broccoli (and other vitamin K-rich vegetables such as kale, spinach, brussels sprouts and collards) consistent week to week. There is no need to weigh portions; the goal is to avoid extreme swings. If you currently eat broccoli once or twice a week, keep doing that. If you have never eaten it and want to start, introduce it gradually and tell your anticoagulation clinic so they can recheck the INR after a few weeks.
Other practical steps: do not start juice cleanses, low-carb plans that emphasize unlimited cruciferous vegetables, or restrictive diets that eliminate all greens without first telling your warfarin prescriber. Get an extra INR check any time your diet, appetite or weight changes significantly, after illness with reduced food intake, or before and after travel where your menu shifts.
Which specific products are affected?
This interaction applies to all vitamin K antagonists, not just warfarin. That includes brand-name Coumadin and Jantoven (warfarin), as well as acenocoumarol (Sintrom) and phenprocoumon (Marcumar) used outside the United States. It does not meaningfully apply to the direct oral anticoagulants such as apixaban (Eliquis), rivaroxaban (Xarelto), dabigatran (Pradaxa) or edoxaban (Savaysa), which do not work through the vitamin K pathway.
On the food side, similar considerations apply to all members of the brassica family with high vitamin K content: kale, collard greens, brussels sprouts, mustard greens, turnip greens, swiss chard, spinach (technically not brassica but very high vitamin K), parsley, and concentrated green smoothies or green-powder supplements such as wheatgrass, spirulina and chlorella mixes. Multivitamins with added vitamin K and bone-health supplements containing K1 or K2 are also relevant; review labels with your pharmacist.
The bottom line
Broccoli is healthy and you do not have to give it up to take warfarin safely. What matters is consistency, not avoidance. Keep weekly broccoli intake roughly the same, tell your anticoagulation clinic about any deliberate dietary change, and rely on regular INR monitoring to catch shifts before they cause a clot or a bleed.