The diagnosis of schizophrenia usually begins with a physical examination conducted by a physician, who will also review the patient's medical history, including any family history of mental illness.

A physician may try to rule out other mental or physical illnesses that may be causing symptoms. Blood or urine tests may be conducted to determine whether medications, substance abuse or illness is contributing to symptoms. Some infections, cancers, nervous system disorders, thyroid disorders, immune system disorders, seizures and head trauma can produce psychotic symptoms. At times, imaging studies such as MRI may be ordered to rule out other conditions that can affect the brain.

A patient will be referred to a psychiatrist who can conduct a psychiatric evaluation, which should include a detailed description of signs and symptoms, a mental status examination and overview of social, family and psychiatric history. Patients with schizophrenia usually begin experiencing symptoms in late adolescence or early adulthood.

In general, a patient must be experiencing psychotic or "loss of reality" symptoms associated with schizophrenia for at least six months to be diagnosed with the disorder. The symptoms must be accompanied by a decreased ability to function in work, school, home and/or social settings.

Schizophrenia can sometimes be difficult to diagnose because many of its symptoms are also symptoms of other mental disorders, such as depression or bipolar disorder. Also, a person with schizophrenia may not be able to recognize the symptoms because they are not thinking straight. In some cases, patients are referred to medical professionals by family members or friends. With early diagnosis and treatment, however, the disorder can be managed more effectively, and some measure of recovery can occur.