Diagnostic labels aim to classify individuals for treatment in clinical settings. Yet, relatively little attention has been paid to the troubling messaging when a diagnostic label itself carries severe stigma and how relevant stakeholders react to it. Based on twenty-month fieldwork in Shanghai, this article analyzes the adverse effects of the diagnostic label chidai that is used to describe dementia and the relevant stakeholders' responses to the labeling threat. It focuses on the moral context in which the stigma related to dementia unfolds, the power of the medical term chidai in activating stigma, and the efforts that are put into formulating a stigma-free public health message. I found that the label chidai is not only an instance of excess stigma-that discredits one's cognitive capability and deprives one's moral status-but also an instrument used by medical authorities and governments to protect public safety. The debates on the diagnostic labels are meant to reshape new understandings of dementia and to challenge the power of medical authorities who often neglect humanity and care when they form their judgments and interpretations of disease. This paper contributes to the studies of stigma and dementia activism by highlighting the power of diagnostic labels.