The functioning of the heart muscle is particularly sensitive to iron deficiency, the easily curable comorbidity most frequently associated with heart failure. Iron-deficient heart failure patients are more often rehospitalized and have reduced survival. Heart muscle function is particularly susceptible to martial deficiency. Recent randomized studies have shown that exogenous iron intake is accompanied by improved functional capacity (walking test), quality of life, and re-hospitalization rate in these patients. The symptoms of iron deficiency are not very specific and often confused with those of heart failure or other comorbidities, which explains why management is often too late. Anemia is only a late consequence of this iron deficiency. Due to the inflammatory state associated with chronic heart failure, only the parenteral route can bypass the macrophage tissue sequestration of iron and inhibit its intestinal absorption. Recent European guidelines recommend screening for iron deficiency (serum ferritin and transferrin saturation coefficient) in all patients with suspected heart failure, routine iron parameters assessment in all patients with heart failure, and intravenous iron supplementation in case of deficiency in symptomatic patients. Given the pejorative nature of iron deficiency on disease progression, the frequency and financial impact of hospitalizations linked to episodes of decompensation, as well as the effectiveness of simple supplementation, screening for this comorbidity, screening for this frequent comorbidity should now be part of routine testing in all heart failure patients.