Since non-medical mental health practitioners are not trained to exclude medical causes of psychosis, people experiencing psychosis should be referred to an emergency department or hospital. Delirium should be ruled out, which can be distinguished by visual hallucinations, acute onset and fluctuating level of consciousness, indicating other underlying factors which includes medical illnesses. Excluding medical illnesses associated with psychosis is performed by using blood tests to measure:

Thyroid-stimulating hormone to exclude hypo- or hyperthyroidism,
Basic electrolytes and serum calcium to rule out a metabolic disturbance,
Full blood count including ESR to rule out a systemic infection or chronic disease, and
Serology to exclude syphilis or HIV infection.Other investigations which may be performed include:

EEG to exclude epilepsy, and an
MRI or CT scan of the head to exclude brain lesions.Blood tests are not usually repeated for relapse in people with an established diagnosis of schizoaffective disorder, unless there is a specific medical indication. These may include serum BSL if olanzapine has previously been prescribed, thyroid function if lithium has previously been taken to rule out hypothyroidism, liver function tests if chlorpromazine has been prescribed, CPK levels to exclude neuroleptic malignant syndrome, and a urinalysis and serum toxicology screening if substance use is suspected. Assessment and treatment may be done on an outpatient basis; admission to an inpatient facility is considered if there is a risk to self or others. Because psychosis may be precipitated or exacerbated by common classes of psychiatric medications, such as antidepressants, ADHD stimulant medications, and sleep medications, prescribed medication-induced psychosis should be ruled out, particularly for first-episode psychosis.
Schizoaffective disorder (SZA, SZD or SAD) is a mental disorder characterized by abnormal thought processes and an unstable mood. This diagnosis is made when the person has symptoms of both schizophrenia (usually psychosis) and a mood disorder: either bipolar disorder or depression. The main criterion for a diagnosis of schizoaffective disorder is the presence of psychotic symptoms for at least two weeks without any mood symptoms present. Schizoaffective disorder can often be misdiagnosed when the correct diagnosis may be psychotic depression, bipolar I disorder, schizophreniform disorder, or schizophrenia. It is imperative for providers to accurately diagnose patients, as treatment and prognosis differ greatly for most of these diagnoses.There are three forms of schizoaffective disorder: bipolar (or manic) type (marked by symptoms of schizophrenia and mania), depressive type (marked by symptoms of schizophrenia and depression), and mixed type (marked by symptoms of schizophrenia, depression, and mania). Common symptoms of the disorder include hallucinations, delusions, and disorganized speech and thinking. Auditory hallucinations, or "hearing voices", are most common. The onset of symptoms usually begins in adolescence or young adulthood. On a ranking scale of symptom progression of mental health issues relating to the schizophrenic spectrum, schizoaffective disorder falls between mood disorders and schizophrenia in regards to severity, with other disorders included on the ranking as well depending on symptoms.