Diabetes and mental disorders are common chronic illnesses in the United States. Recently, the introduction of a new class of atypical antipsychotic medications has been a major treatment advance for patients with mental disorders. Because of increased use of atypical antipsychotic medications, new and unanticipated side effects have often appeared. Treatment-emergent diabetes has been described for conventional and atypical antipsychotics. People with schizophrenia may be at increased risk for type 2 diabetes because of the side effects of antipsychotic medication, underlying predisposition, and less healthy lifestyles.