BackgroundAsthma is a heterogeneous disease characterized by chronic airway inflammation. The pathophysiologic processes of asthma can disrupt iron homeostasis, resulting in anemia. However, the association between asthma and anemia among adult asthma patients remains limited. Therefore, the main aim of this study was to determine the prevalence and factors associated with anemia among adult asthmatic patients from May to August 2021.MethodsAn institution-based, cross-sectional study was conducted among 291 asthmatic patients in Northwest Ethiopia. A pre-tested structured questionnaire and checklist were used to collect sociodemographic and clinical data. A blood specimen was collected from asthmatic patients for a complete blood count analysis and morphology assessment. The data were entered into the Epi data software and exported to the statistical package for social science version 20 software for analysis. Non-parametric Mann-Whitney U test was used to compare red blood cell parameters among groups with acute and chronic exacerbations. Binary logistic regression models were used to determine the factors associated with anemia. A p-value less than 0.05 was considered statistically significant.ResultThe overall prevalence of anemia in this study was 11% (95% CI: 7.2–14.8%). Acutely exacerbated asthmatic patients had significantly lower median values of red blood cell parameters such as red blood cell count, hemoglobin, and mean cell hemoglobin when compared to chronic exacerbations. In addition, using systemic corticosteroids (AOR = 4.07, 95% CI: 1.126–14.71, p = 0.032) and being hospitalized in the emergency department (AOR = 3.74, 95% CI: 1.26–11.07, p = 0.017) were found to be significantly associated with anemia.ConclusionThis study demonstrated that anemia was predominant in adult asthma patients. Red blood cell number, hemoglobin level, and mean corpuscular hemoglobin were significantly lower in acute asthma exacerbations. Therefore, appropriate intervention strategies should be undertaken to reduce the prevalence of anemia among adult asthma patients to reduce further complications and provide better monitoring of asthma patients.