Based on FDA | Does olive oil interact with warfarin or affect INR levels due to its vitamin K content?

Olive oil and warfarin: what to know about INR and vitamin K

Short answer: Olive oil contains small amounts of vitamin K, and very large or sudden changes in your intake of oils (including olive oil) can theoretically lower INR by counteracting warfarin’s effect. However, routine culinary use in consistent amounts is generally acceptable; the key is to keep your intake steady rather than eliminate olive oil. ^{[1] [2] [3]}

Why vitamin K matters with warfarin

• Warfarin works by blocking vitamin K–dependent clotting factors; increasing vitamin K intake can reduce warfarin’s effect and lower your INR (making blood “thicker”). ^{[1] [4]}
• Official prescribing information and patient education materials advise avoiding large amounts of vitamin K–rich foods and certain vegetable oils because they can lower INR. ^{[5] [6] [3]}

Where olive oil fits

• Educational guidance for people on warfarin lists “some oils, such as canola, olive, and soybean oils” as items to keep consistent day‑to‑day or week‑to‑week, rather than avoid entirely. Consistency is the priority. ^{[2] [7] [8]}
• Intravenous lipid emulsions that include olive oil explicitly contain vitamin K and may counteract anticoagulation, underscoring that oils can carry vitamin K; this supports the principle that higher vitamin K exposure can reduce INR. ^{[9] [10]}

Evidence on diet changes and INR

• Controlled studies show that increasing dietary vitamin K (for example, from vitamin K–rich vegetables or supplements) can meaningfully reduce warfarin effect and push INR below the therapeutic range. This demonstrates the general mechanism: more vitamin K → lower INR. ^[11]
• Broader reviews of warfarin interactions consistently identify “foods high in vitamin K” as reducing warfarin’s effect; while many reports focus on greens, oils with vitamin K also contribute to total intake. ^{[12] [13]}

Practical guidance for olive oil use

• You usually do not need to eliminate olive oil. Use typical culinary amounts and keep your pattern stable (for example, similar portions of dressings, sautés, and cooking oils each week). ^{[2] [3]}
• Avoid sudden large increases, such as switching abruptly from low‑oil cooking to multiple tablespoons daily, which could lower INR and require dose adjustments. Talk with your clinician before major diet shifts. ^{[1] [3]}
• If you start or stop higher‑vitamin‑K oils (olive, soybean, canola) in notable amounts, more frequent INR checks are sensible to keep your anticoagulation in range. ^{[14] [15]}

Comparison: vitamin K influences on INR

• Vitamin K–rich vegetables and supplements can substantially reduce INR when intake rises abruptly. Oils contribute vitamin K but typically at smaller amounts per usual serving; their impact becomes clinically relevant mainly with large or sudden changes. ^{[11] [2] [3]}

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Quick reference table

Item	Vitamin K relevance	Typical advice on warfarin
Leafy greens (kale, spinach, etc.)	High vitamin K	Limit large amounts; keep intake consistent. [1] [5] [3]
Vegetable oils (olive, soybean, canola)	Contain vitamin K (lower than leafy greens per typical serving, but not zero)	Use normal culinary amounts; avoid sudden large increases; keep intake consistent. [2] [8] [3]
Vitamin K supplements (phytomenadione)	Very high vitamin K	Can markedly lower INR; avoid unless directed by clinician. [11]
Lipid emulsions with olive oil (IV)	Contain vitamin K and can counteract anticoagulation	Monitor anticoagulation if receiving such products. [9] [10]

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Key takeaways

• Olive oil has some vitamin K, so big or abrupt increases in use can reduce warfarin’s effect and lower INR, but steady, everyday amounts are generally fine. ^{[2] [3]}
• Focus on consistency in all vitamin K sources greens, oils, and supplements and arrange INR monitoring with any notable dietary change. ^{[1] [14] [15]}

If you’re planning a significant change in cooking oils or diet pattern, it’s wise to arrange an extra INR check and let your care team know in advance. ^{[14] [15]}