- Introduction Azacitidine (AZA) dose reduction is a common practice in cytopenic patients. However, a correlation between AZA dose and infection complications has never been studied. Patients and Methods Higher-risk patients with myelodysplastic syndrome or acute myeloid leukemia treated with AZA in 18 Israeli hospitals between the years 2008 and 2011 were included in a former national survey. To reveal the effect of AZA dosage on infection risk we limited our analysis to the infection rate after the first AZA dose alone. We excluded subsequent cycles of AZA from the analysis, because infectious events during these cycles might be related to other cofactors such as disease response to AZA therapy. Results After the first AZA cycle, infectious events were more frequent after doses of 75 mg/m2 for 7 days than 75 mg/m2 for 5 days (36/106 [34%] and 10/67 [14.9%], respectively; P = .008), regardless of the patient's age. Of the 46 recorded infectious events, the causative pathogen was identified as bacterial in 25 (54.3%) and as viral or fungal in 2 (4.3%) and 2 (4.3%) cases, respectively. No pathogen was identified in 17 (37%) cases. Infections were significantly more prevalent among patients who presented with platelet counts < 20,000 (43.6% vs. 23.6%; P = .012) and poor risk cytogenetics (40.7% vs. 19.8%; P = .008). Conclusion Reduction of AZA dose might decrease infection rate and therefore should be considered in patients with high infection risk.