Common Causes and Diagnostic Approaches to Anemia in Hospitalized Adults

Anemia remains a frequent and clinically significant finding among hospitalized adults, often complicating medical and surgical conditions and contributing to longer hospital stays, increased morbidity, and delayed recovery. The etiologies are broad, including anemia of chronic disease, iron deficiency, acute blood loss, nutritional deficiencies, renal dysfunction, bone marrow suppression, and hemolysis. Patients admitted for various reasons often present with overlapping causes, making diagnosis and management complex. Inflammation and infection can obscure typical laboratory patterns, while hospital-related factors such as phlebotomy, poor nutrition, and medication effects can exacerbate pre-existing anemia or create new deficits. Accurate diagnosis begins with a structured evaluation of red blood cell indices and classification by mean corpuscular volume, followed by targeted testing such as reticulocyte counts, iron studies, vitamin B12 and folate levels, and markers of hemolysis. The interpretation of results must consider acute illness and coexisting conditions. Underdiagnosis of reversible forms of anemia, particularly nutritional deficiencies, remains common and may affect functional outcomes after discharge. Clinical judgment is essential in decisions around red blood cell transfusion, iron replacement, or the use of erythropoiesis-stimulating agents. Management strategies vary by etiology and patient context. Restrictive transfusion thresholds have been shown to be safe in stable patients, while intravenous iron and vitamin supplementation can be effective in hospitalized populations when used appropriately. Integration of diagnostic algorithms into hospital workflows and increased awareness of the multifactorial nature of anemia can improve outcomes and resource utilization. Attention to anemia during hospitalization provides an opportunity to address reversible causes, reduce readmissions, and support overall recovery.