In adults with iron deficiency anemia (IDA), abnormal platelet counts were seen in several studies. However we retrospectively examined the clinical records of a larger number of adults with IDA to assess abnormal platelet counts. From November 2006 to April 2008, 615 consecutive adults (73 men and 542 women; age range, 16-88 years) with IDA were included in this study. The mean initial hemoglobin was 9.0 +/- 1.8 g/dL (range 2.7-12.8 g/dL), and the mean initial platelet count was 304 x 10(3)/microL +/- 92.3 (range, 105-700 x 10(3)/microL). The initial platelet counts were normal in 520 (84.6%) adults with IDA. Thrombocytosis (>400 x 10(3)/microL) and thrombocytopenia (<150 x 10(3)/microL) were detected in 82 (13.3%) and 13 (2.1%) adults with IDA, respectively. In conclusion, thrombocytosis was seen at lower rates in our study. Furthermore, this study shows that mild thrombocytopenia is not so rare in adults with IDA.