Clozapine is an atypical antipsychotic medication, used primarily as the drug of choice in treatment resistant schizophrenia. Despite its considerable advantages, clozapine’s licence is restricted because of its potential to induce agranulocytosis. Hence, white blood cell count monitoring is mandatory in patients receiving clozapine treatment. A side effect of clozapine that has received relatively less attention is constipation, which is caused by the drug’s anticholinergic effect. This potentially serious problem can result in life- threatening bowel obstruction, ischemia, necrosis, perforation, and pulmonary aspiration. Despite this evidence, routine inquiry about constipation in clozapine treated patients is not emphasised in current clinical guidance. We report a case to highlight constipation as both a potentially serious side effect and as a factor, insufficiently recognised, in non-adherence to clozapine.