Vitamin K lowers your INR values. The lower your INR, the less time it takes for your blood to clot. A low INR means that warfarin isn't working well enough to prevent a dangerous blood clot. Warfarin raises your INR values. The higher your INR, the more time it takes for your blood to clot.

Vitamin K - Eating an increased amount of foods rich in vitamin K can lower the PT and INR, making warfarin less effective and potentially increasing the risk of blood clots. People who take warfarin should eat a relatively similar amount of vitamin K each week.

Certain foods and dietary supplements have vitamin K. Vitamin K works against warfarin. If you eat more vitamin K, it can lower your INR. If you eat less vitamin K, it can raise your INR.

Evidence from randomized controlled trials supports the use of low-dose oral vitamin K therapy as a treatment that promptly reduces the INR. Vitamin K given orally is more effective than subcutaneous vitamin K injection, and as effective as intravenous administration when INR values are compared 24 hours after administration.