In addition to potentially improving warfarin dosing for atrial fibrillation (still being used commonly around the world despite the rise of novel oral anticoagulants) the methodology described in this paper may have important applications in other clinical domains, including dosing of warfarin for other indications (such as patients with mechanical valves) as well as optimization of other medications where dosing is based on sequential dose–response relationships, such as heparin, insulin, oral antihyperglycemic drugs, and phenytoin. This evidence concerns the gene INS and atrial fibrillation.