Hi there, Welcome to Justanswer! I am Dr. Hoellering and pleased to help you. Please tell your mother in law not to take any warfarin today and until Saturday. Saturday the usual 1/4. She does not have to take any action but please be careful walking. If she hits herself or falls, she might bleed more than usual. The blood level of warfarin will rise, but fall again slowly when she will pause for three days. Then the anticoagulation will be in the normal range again. Don't hesitate to ask if anything is not clear yet. All the best for you mother in law!