Introduction <p>Iron deficiency (ID) is a common comorbidity in patients with heart failure (HF). It is associated with reduced performance, frequent hospitalizations and low quality of life. There is an ongoing debate about the correct definition of ID in HF.</p> Purpose <p>Refinement of the ID determination in patients with advanced HF. Evaluation of the association of iron metabolism parameters with other clinical characteristics.</p> Patients and methods <p>One hundred-two patients with advanced HF were included, 48 in-patients, out-patients without LVAD and 25 of patients with LVAD implanted. In addition to conventional tests, we monitored iron metabolism parameters. The prevalence of ID was compared according to both the original and the updated ID definition. Correlations between individual iron markers and patients’ functional capacity were measured.</p> Results <p>The prevalence of ID in patients with advanced HF was 65%. There was no statistically significant difference in individual iron parameters between the groups. All parameters except ferritin correlated with NT-proBNP in the in-patient group. Serum iron correlated most strongly with NT-proBNP and CRP across all groups. The sTfR parameter correlated the most with right heart catheterization parameters, serum iron and TSAT were the most specific parameters related to functional status.</p> Conclusion <p>Patients with more advanced HF and severe limitation of functional capacity had worse iron parameters. Ferritin seems to be the less specific marker of ID, while detecting ID using serum iron and TSAT seems to be reliable. The correlation of ferritin with functional status or haemodynamics was the weakest of all the parameters studied.</p> Graphical Abstract <p></p>