How many people are affected by warfarin sensitivity ?
The prevalence of warfarin sensitivity is unknown. However, it appears to be more common in people who are older, those with lower body weights, and individuals of Asian ancestry.  Of the approximately 2 million people in the U.S. who are prescribed warfarin annually, 35,000 to 45,000 individuals go to hospital emergency rooms with warfarin-related adverse drug events. While it is unclear how many of these events are due to warfarin sensitivity, the most common sign is excessive internal bleeding, which is often seen when individuals with warfarin sensitivity are given too much of the medication.