The aim of current study was to evaluate the function of thyroid during diabetic acidosis, just after the treatment and two weeks after the treatment. This was the analytic study. The study subjects included 20 patients, aged 18-36 years old, with type1 diabetes and diabetic ketoacidosis. All subjects were evaluated for thyroid function tests such as triiodothyronine (T3), thyroxine (T4), T3 resin uptake (T3RU), free T3 (FT3), free T4 (FT4) and thyroid stimulating hormone (TSH), before treatment. After completing DKA treatment and two weeks after discharge, the thyroid function tests were repeated on the subjects and the results were analyzed using paired T-test, ANOVA or repeated measure and Pearson correlation tests. the current study showed that the mean levels of T3 and T4 were at hyperthyroid range and lower than normal before the treatment and significantly increased after the treatment (P