Whether diabetes could prevent attacks of acute intermittent porphyria (AIP) remains incompletely understood. Lithner described 16 AIP patients who had complete remission of AIP attacks after onset of diabetes [1]; however, a correlation between blood glucose level and frequency/severity of AIP attacks was not mentioned. Can AIP be excluded in a diabetic patient who visits ED for severe abdominal pain? AIP is a very rare hereditary metabolic disorder in Taiwan; herein, we reported a patient who had diabetes antedated AIP.