© 2015 Society for Psychotherapy Research. Objective: The interpersonal theory of suicide argues that suicidal ideation predicts self-injury. We hypothesized that distinct patterns of suicidal ideation could be identified and these ratings could allow early identification of self-injury. Method: The sample consisted of 562 psychiatric inpatients who reported suicidal ideation. Results: Latent growth class analysis identified five classes of change in suicidal ideation. Patients who displayed prolonged suicidal ideation could be identified with improved sensitivity (89.66%) and negative predictive power (94%), compared to a model based on routine ratings of suicidality at admission (sensitivity = 50%; negative predictive power = 74%). These patients had a fourfold increased risk of self-injury. Conclusions: Daily measurement of suicidal ideation may identify inpatients at risk and inform clinical decision-making.