Hello, warfarin is a peculiar drug. There are so many things that affect its effectiveness, which make it - sometimes - difficult to take the right dosage. A patient who takes warfarin should make no diet changes, avoid alcohol, avoid taking other drugs and check the INR regularly. Vegetables are not prohibited! The patient should adjust the dosage according to the diet. Other factors that affect warfarin include infections, thyroid function etc. I couldn t name them all. They are just too many. Try to remember whether anything different than usual happened the last few days or if you took (or ate) anything at all that s not in your usual routine, including herbs, vitamins, cranberries etc. I know it s hard, but you should be prepared that you are going to have strange results from time to time. Adjust the dose slowly and stay alert for symptoms of overdosing. When you have a strange result do not wait until the next month to check again. Do the necessary (gradual) change and check again in a few days. I hope I ve helped! If you d like to ask more, please let me know. I ll be glad to help. Kind Regards!