Purpose(1) To determine the characteristics of seizures and/or epilepsy among patients with adult onset type 1 diabetes mellitus (T1DM), and (2) to determine glutamic acid decarboxylase antibody (antiGADab) titres and other autoimmune characteristics of T1DM patients with seizure and/or epilepsy. MethodsPatients were recruited after reviewing the databases of one Diabetes Unit and two Epilepsy Units. Prevalence of suffering epilepsy and/or seizures was calculated in the group of adult onset T1DM patients seen consecutively in the Diabetes Unit. Serum antiGADab titres were determined in all patients. ResultsAmong the 229 T1DM patients, two had suffered hypoglycemic seizures (0.87%) and two unprovoked seizures (0.87%). We recruited 11 of these T1DM patients. Five reported only hypoglycemic seizures, and 6 temporal lobe epilepsy (TLE).Mean antiGADab titres in patients with T1DM and hypoglycemic seizures were lower (18.42IU) than in those with T1DM and TLE (29.200IU), p: 0.006. Patients with T1DM and TLE suffered more other autoimmune diseases than those with T1DM and hypoglycemic seizures, p: 0.015. ConclusionsHypoglycemic seizures are rare in T1DM patients. AntiGADab titres do not differ from the general diabetic population. Patients with high titres of antiGADab are more likely to develop TLE.