Alcohol use also may affect your response
to warfarin. Excessive use can lead
to a sharp rise in your INR. It is best
to avoid alcohol while you are taking warfarin.
I have been on warfarin for 6 months now for DVT, my INR should be between 2-3. It has been quite stable.
Make sure your Father keeps a check on his diet. Consistency is everything when taking Warfarin.
Stress, sleep changes, diet, other medication, even the time of day that the blood is taken can all affect the INR level.