Self-cutting is a symptom of certain types of mental illness. However, it is generally not an indication that the patient is considering suicide.
Self-cutting and other forms of self-harm can indicate many psychiatric disorders such as borderline personality disorder, clinical depression, anxiety, substance abuse, anorexia nervosa, bulimia, post-traumatic stress disorder, schizophrenia and other personality disorders. It is often consistent with a medical history of abuse.
In Control, House learns that Carly Forlano has been self-cutting.
In Act Your Age, Cameron suggests, as an explanation, that Lucy may have cut herself, though Chase thinks that she's too young for self-cutting.
In Merry Little Christmas, Cameron learns that House cut himself to deal with his pain due to Vicodin withdrawal.
In Bombshells, Taub accuses Ryan of self-cutting.