Pharmacogenetic testing is currently not routine in critical care settings but recent changes in the warfarin label are likely to lead to critical care nurses encountering physician or nurse practitioner orders for such testing. Although the science for pharmacogenetics is complex, the components of patient teaching are not beyond that which nurses already provide about other laboratory, disease, and treatment-based information. It is reasonable to expect that as the science of pharmacogenetics and pharmacogenomics expands and discoveries are translated in clinical settings, the additional information from pharmacogenetic test results will help prescribers select or adjust medication doses to reduce the risk for adverse drug reactions and improve the chances of achieving therapeutic targets in a timely fashion.