Test Details: Warfarin sensitivity testing helps determine if you may be more sensitive (i.e., require lower doses) to treatment with warfarin because of your genetic makeup. This test primarily detects common genetic variations in two genes, CYP2C9 and VKORC1. A healthcare practitioner may sometimes order this test to help select appropriate doses of warfarin and/or to achieve appropriate dose levels more quickly. Genetic testing for warfarin sensitivity may help to shorten the time it takes for you to reach a stable dose; that is, to achieve adequate "blood-thinning" without bleeding episodes. Most often, it is determined that people are more sensitive to warfarin and may need smaller doses; however, there are some people who are less sensitive and may need larger doses.