Warfarin is a medication commonly known as a blood thinner (anticoagulant). It is used to decrease the risk of blood clot formation and prevent existing blood clots from growing and breaking off. The primary danger from blood clots is when they get lodged in narrow arteries, for example in the brain (causing stroke) or in the lungs (causing pulmonary embolism).
Determining the appropriate dose for someone starting warfarin therapy is extremely challenging, since the dose required for recommended therapeutic levels differs between individuals due to genetic and environmental factors (age, weight, diet and other drugs). Having genetic test done, would greatly help your physician determining the initial warfarin dose and minimize your risk of developing side effects.
More information about genetic testing for medications.