Because everybody is different and everyone needs a different dose of warfarin when you start taking warfarin, you will have a lot of blood tests to help your doctor find the right dose for you. Initially you will need a blood test daily or every second day until the right dose is found. It takes about a week to find the right dose for most people.
Once you have found the right dose a blood test is usually only needed every few weeks. The frequency of tests is different for everybody.
There are some instances where you will need to have your INR tested more frequently for a while. If you get sick, quit smoking, or start a new diet your INR will probably change with the change in your lifestyle. Your doctor may want to keep a closer eye on your INR at these times.
After each blood test your dose of warfarin may be changed to keep the INR within your target range.