ObjectiveTo examine characteristics of hospital admissions and risk factors associated with rehospitalization for self-poisoning with medications in adolescents aged 10–19 years. MethodThis study used data from the Norwegian Patient Register from 2008 to 2011. The main outcome was hospital readmission within the observation period. A complementary log–log regression model was used to assess the effect of characteristics at index hospital admission on readmission. ResultsOf 1497 patients, 76.4% were females and 89.8% were aged 15–19 years. At their first hospital admission, about one third received a secondary psychiatric diagnosis. Females (47.5%) were registered with an E-code for intentional self-harm more often than males (33.7%), and females were more often than males discharged to further treatment (27.8% vs. 21.5%). As many as 18.4% were rehospitalized for self-poisoning by medications. Significant predictors for hospital readmission were female sex [hazard ratio (HR)=2.4, 95% confidence interval (CI) 1.7–3.6], discharge to further treatment (HR=2.3, 95% CI 1.8–2.9) and psychiatric secondary diagnoses (HR=1.5, 95% CI 1.2–1.9). ConclusionThis national study demonstrated significant sex differences in adolescents treated in hospital for self-poisoning with medications. Psychiatric secondary diagnoses had a strong predictive effect on readmission, which indicates the importance of psychiatric/psychosocial assessment of adolescents who are admitted to hospital for self-poisoning with medications.