Normally, INR range should be between 2.0 to 3.0, according to Mayo Clinic. In some situations a higher INR range is best. It is normal for INR ranges to fluctuate to some degree, and changing the dosage of medication may take days to affect INR.
A high INR means that the blood clots more slowly than it should, while a low INR means that the blood clots much faster than it should, notes Mayo Clinic. A vitamin K deficiency may cause slow clotting, while vitamin K supplements may cause the blood to clot too fast. Many other conditions such as liver problems, estrogen and congenital factor deficiency can cause INR changes, which is why it is monitored so carefully.