This chapter addresses the practicalities of assessing an individual’s medical decision-making capacity, specifically during the pre-operative risk phase and the post-operative behaviour assessment in surgical contexts. By utilising fieldwork data, Body Integrity Dysphoria (BID) is compared to other types of invasive medical procedures, such as gastric banding and sleeve gastrectomy. Such a daring comparison emerged unexpectedly during the interview phase, and it is used to assess the psychological criteria that current medical professionals use to differentiate between those eligible to undergo such procedures and those who are not. By leveraging on gastric banding and sleeve gastrectomy, the chapter aims at addressing one of the most frequent oppositions moved against amputation as a potential therapeutic approach to BID: the patient’s regret post-surgery. It is argued that there cannot be medical certainty on the outcome of any surgical procedure, particularly those done to address psychological state. The opposition to BID regret post-amputation, therefore, seems to be beyond what is currently considered an acceptable standard for similarly invasive medical practice.