en عمومى General پژوهشي Research <div><strong>Background: </strong>This study was conducted to determine whether type 1 diabetes mellitus (T1DM) is associated with ABO & Rhesus (Rh) blood groups.<br> <strong>Materials and Methods: </strong>This analytical cross sectional study was carried out on 77 patients suffering from T1DM and 96 healthy children less than 18 years old referring to Yazd Diabetes Research Center from April 2018 to May 2019. The ABO blood group and Rh factor in both groups were determined. Fasting blood sugar (FBS) and hemoglobin A1C (HbA1c) were measured at baseline, 12 weeks, and 24 weeks in these patients, and the mean of FBS and HbA1C in three-time assessments were considered as the FBS and HbA1C variables. The statistical analysis was performed by SPSS software version 22.<br> <strong>Results: </strong>About 46.8% in T1DM and 36.5% in the control groups were male. There was a significant difference between groups regarding blood groups (p-value: 0.042). Although the frequency of B+ was 33.8% and 19.8% in the T1DM and controls, respectively, AB+ and O+ were more prevalent in the controls. The mean of FBS was significantly different between groups (p-value: 0.023).</div> <strong>Conclusions: </strong>The findings revealed that patients with blood group B are more likely to develop T1DM whereas those with blood group O showed a lower tendency towards diabetes. Blood Group Antigens, Child, Diabetes Mellitus, Rh-Hr Blood-Group System 49 54 http://ijpho.ssu.ac.ir/browse.php?a_code=A-10-515-1&slc_lang=en&sid=1 Mahtab Ordooei dr.ordooei@yahoo.com. 0000-0002-2466-9070 No Children Growth Disorder Research Center, Shahid Sadoughi University of Medical Science, Yazd, Iran Children Growth Disorder Research Center, Shahid Sadoughi University of Medical Science, Yazd, Iran Nasim Namiranian namiranian.nasim@gmail.com. 0000-0002-5133-6204 No Community medicine specialist. Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Community medicine specialist. Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Hadi Jalali Hadijalali1314@gmail.com. No Central Medical Laboratory of Yazd. Iran. Central Medical Laboratory of Yazd. Iran. Saeede Jam saeedehjam@ut.ac.ir 0000-0002-0375-2107 No Researcher, Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd,Iran Researcher, Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd,Iran Azam Golzar golzar_azam@yahoo.com 0000-0002-0403-2742 Yes Hematology and Oncology Research Center, Shahid Sadoughi University of Medical Science, Yazd, Iran. Hematology and Oncology Research Center, Shahid Sadoughi University of Medical Science, Yazd, Iran.