Background: Hemoglobin A1C (HbA1c) is the predominant hemoglobin found in HbA1rnfractions. The International Expert Committee recommends A1C assay is accurate, precisernmeasures of chronic glycemic levels thus recommend the use of HbA1c for diagnosing diabetes.rnOn the other hand, the committee stated any condition that changes red cell turnover, such asrnsickle cell anemia, hemolytic anemia, chronic malaria, major blood loss, or blood transfusions,rniron deficiency anemia (IDA), renal failure will lead to spurious A1C results.rnObjective: To determine the effect of IDA on HbA1c in diabetic patients in Tikur AnbessarnSpecialized Hospital, Addis Ababa, Ethiopia.rnMethod: A case-control study was conducted to assess the effect of IDA on HbA1c in diabeticrnpatients from April to July 2016. A convenient sampling method was used and 174 diabeticrnpatients (87 IDA and 87 without IDA) were included in the study. CBC (Complete blood count),rnSerum ferritin were performed by Cell dyn 1800 hematology analyzer, COBAS INTEGRA 400rnplus 800 Chemistry analyzer and HbA1c by COBAS C 111 analyzer respectively for the IDArnand control group. The data was entered into Excel Spread sheet and exported to StatisticalrnPackage for Social Sciences (SPSS) version 21 software systems for analysis. Pearson‟srncorrelation, chi-square, independent t-test was calculated. The data was presented as mean ± SD.rnP-value of