How can my diet or medications affect how warfarin works?

Changes in diet can modify warfarin's effects, especially if your vitamin K intake changes. For instance, suddenly eating lots of green leafy vegetables, which are loaded with vitamin K, might diminish the benefits of a warfarin dose that has been working well.

Medications such as antibiotics, nonsteroidal anti-inflammatory drugs, and certain antidepressants can intensify the action of warfarin; so can alcohol. Let your doctor know if you use any of these.