They now have meters which test the INR that are very similar to a glucometer to test blood sugar. We had talked with our doctor about that when my DH was on warfarin. They had a high rate of incorrect readings when they first came out, but they got the bugs worked out. Our cardiologist eventually told us we could use one. But he no longer needed the warfarin, so he is off of it now.
I would ask your doctor if you could use the meter and self test. They would have to provide you with the scale to adjust your dose, or you could call it in when you test.
This would be the easiest and no cost to you.
INR MetersDale