We report a patient with schizophrenia who developed diabetes mellitus during treatment with olanzapine. The case confirms the pattern of atypical antipsychotic-related diabetic emergencies: rapid onset in relatively young patients, often with severe glucose derangements and serious complications. As diabetic emergencies have a high morbidity and mortality, regular glucose screening should be performed in patients with schizophrenia treated with atypical antipsychotics.