Gene Variant in Blacks Alters Warfarin Response

I'm sure your doctor will tell you about this before you bring it up to them.
http://www.medpagetoday.com/Cardiology/Strokes/39631?
The first genome-wide association study to focus on warfarin dose in African Americans found a genetic variant that explains their variable response to the blood thinner.
African Americans with one copy of the rs12777823 variant would need to reduce their warfarin dosage by 6.92 mg per week to obtain its full benefits, according to Julie Johnson, PharmD, of the Center for Pharmacogenomics at the University of Florida in Gainesville, and colleagues.
Those of African descent with two copies of this single-nucleotide polymorphism (SNP) would require a dose reduction of about 9 mg/week, a good portion of the 40 mg average weekly dose for African Americans, researchers reported online in The Lancet.

Rest at link.