With the rise of The Diagnostic and Statistical Manual of Mental Disorders (DSM), and a diagnosis-centred culture, an increasing number of authors are examining the stigmas surrounding hypochondria, hysteria, and medical malingering. Despite these critical trends, the diagnosis of mental illnesses and cognitive disabilities remains controversial in public discourse, and while contested illnesses are increasingly represented in literature and film, the consequences of the public suspicion of these conditions are seldom explored. Drawing on methodologies from within cultural disability studies, this article introduces Alasdair Gray’s award-winning novel Poor Things (1992) as an interrogation of the complexities of modern diagnosis.