Introduction Iron deficiency anemia (IDA) is a common comorbidity among patients with heart failure (HF). There is ongoing data suggesting the importance of balanced iron homeostasis amongst patients with HF. However, little is known about the clinical impact of IDA in patients with HF with preserved ejection fraction (HFpEF) and HF with reduced ejection fraction (HFrEF). Hypothesis The aim of this study was to assess the impact of IDA on HF hospitalizations by HF subtype, i.e. HFpEF and HFrEF. Methods We queried the National Inpatient Sample (NIS), Health Care and Utilization Project (HCUP) database from 2008 to 2014 for patients ≥ 18 years old with a primary discharge diagnosis of HF based on the Clinical Classifications Software code 108. Patients were further stratified to HFpEF using ICD-9 codes 428.3x and HFrEF using ICD-9 codes 428.2x, and 428.4x. IDA was identified using ICD-9 codes 280.1, 280.9, and 280.8. Primary outcome of interest was length of stay (LOS) and total hospital charges by HF subtypes. Secondary outcome was readmission score estimated using Elixhauser-based comorbidities by HF subtypes. Multivariable- adjusted regression models were used to examine the impact of IDA on outcomes. Hospital trend weights were accounted in all models. All analyses were performed using SAS 9.4. Results A total of 1,684,227 patients with primary diagnosis of HFpEF (mean age 76±13, 64% female) and 2,675,477 patients with primary diagnosis of HFrEF (mean age 71±15, 41% female) were identified and included in the study. Prevalence of IDA was significantly higher among patients with HFpEF as compared to HFrEF (6.1 vs. 4.6%, p Conclusions Prevalent IDA is associated with significantly longer hospital stay, higher total hospital charges, and increased likelihood of readmission in both HFpEF and HFrEF patient populations. Parallel clinical results in both HFpEF and HFrEF implicate a potential benefit of addressing IDA in all HF patients regardless of subtype.