If liver injury occurs on methimazole, care should be taken to monitor liver function and discontinue the drug when appropriate. Patients using methimazole who develop jaundice, dark urine, light-colored stools, or other evidence of hepatic dysfunction should discontinue the drug immediately and contact a clinician for evaluation of liver function. If aminotransferase reaches 3 times the upper limit of normal and does not improve on review after 1 week, it should not be continued. After discontinuation, weekly liver function tests should be performed until normalization occurs. If the patient does not return to normal, immediate referral to a hepatologist or gastroenterologist may be necessary. Patients are advised to go to the hospital as soon as the above symptoms occur, and to treat or change the treatment plan under the evaluation of the doctor to avoid delay.