Shared decision making (SDM)-when clinicians and patients make medical decisions together-is moving swiftly from an ethical ideal toward widespread clinical implementation affecting millions of patients through recent policy initiatives. We argue that policy initiatives to promote SDM implementation in clinical practice carry the risk of several unintended negative consequences if limitations in defining and measuring SDM are not addressed. We urge policy makers to include prespecified definitions of desired outcomes, offer guidance on the tools used to measure SDM in the multitude of contexts in which it occurs, evaluate the impact of SDM policy initiatives over time, review that impact at regular intervals, and revise SDM measurement tools as needed
