My mom(87) is on warfarin 2.5 daily and, 5 one day a week. It was pretty regular at that.then a pacemaker was put in and the numbers were up and down.she had a 1.8and was increase to5 for about 3days and, 2.5 for two days. Now the reading is 2.8 and she was increased to 5 mg for 6 days and 2.5 one day only? Why is a need to increase when one is between 2 and 4?