The diagnosis of paranoid schizophrenia usually begins with a physical examination that includes a medical history. A physician will also inquire about 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 and immune system disorders can produce psychotic symptoms. Psychosis may also be a side effect of some medications.

A patient may be referred to a psychiatrist, who will likely conduct a psychiatric evaluation, which may include a description of signs and symptoms and an overview of psychiatric history.

In general, a patient must be experiencing psychotic symptoms or “loss of reality” for at least six months to be diagnosed with schizophrenia. After diagnosing schizophrenia, a mental health professional may attempt to determine what type of schizophrenia a patient has by evaluating symptoms.