Hi, dear I have gone through your question. I can understand your concern. Thimazole(Methymazole) is a antihyperthyroid agent indicated for the treatment of hyperthyroidism, goiter and Graves disease.Hepatic side effects have included hepatitis and jaundice which may persist for several weeks following discontinuation of the drug. Hypoglycemia have been reported like a rare metabolic side effect of Thimazole.Anyway i suggest to consult an endocrinologist and to discuss with him your problem of hyperglicemia during thimazole therapy. My opinion is that maybe there are other factors that can be the culpit of your actual unstable Diabetes that must be taken in consideration. Hope i have answered to your question. Thank you for using HCM. Wish you good health.