What causes an INR level to be low?

A low international normalized ratio is caused by an excess of foods or supplements containing vitamin K, states Mayo Clinic. Medications containing estrogen, hormone replacement therapy and birth control pills can cause low INR values as well.

Foods that contain high levels of vitamin K include chickpeas, green tea, liver, broccoli, kale, turnip greens and soybeans, according to Mayo Clinic. A healthy INR value is 2 to 3, and a high value indicates the blood clots too slowly. A low INR number indicates the blood clots quicker than normal. The prothrombin time blood test measures how long it takes for blood to clot, and the result is reported in either time in seconds or time as a ratio, or INR.