Vitamin K (VKORC1)

VKORC1 (vitamin K epoxide reductase) is the target enzyme of warfarin and part of the vitamin K cycle. The rs9923231 variant is associated with altered warfarin sensitivity and, on average, a lower dose requirement. CYP2C9 affects the metabolism of S-warfarin; CYP4F2 variants contribute to dose variation in some populations. Guidelines use genetic results within validated algorithms that also account for clinical factors.

These markers do not determine vitamin K status and are not sufficient for a warfarin dose decision. When clinical genotype results are available, they may be used with factors such as age, body size, interacting medicines and target INR in a validated algorithm. Treatment still requires clinical oversight and INR monitoring.

Genetic influences on warfarin dose have been studied, but their predictive value depends on population and clinical context. Genome displays markers as technical evidence and does not derive a treatment recommendation from them.