The concept of medical necessity plays a central role in many healthcare systems, including Canada's, by helping determine which healthcare services will receive funding. Despite its significance in health policy frameworks, medical necessity has proven to be notoriously difficult to define and operationalise. A shift toward a more personalised and genetically‐informed approach to the provision of healthcare seems likely to heighten associated policy challenges. One of the stated goals of personalised medicine is to save healthcare systems money by facilitating the (...) use of less and more effective treatments. However, any cost saving potential may ultimately be thwarted by physicians' legal and ethical obligations, given that physicians will inevitably be required to implement and define the bounds of genetically‐informed medical necessity for their patients. (shrink)