Iron is an essential trace metal, vital for various physiologic processes, but excess levels can harm health. Maintaining iron homeostasis is critical, with hepcidin playing a key role. The isoform hepcidin-25 exerts the most significant influence on iron metabolism, making its serum levels a valuable diagnostic tool. However, mass-spectrometry and other conventional measurement methods can be difficult to perform, and some immunoassays lack reliability. In this study, we employed a recently developed latex agglutination method integrated with a readily available automated analyzer to quantify serum hepcidin-25 levels in both volunteers recruited from personnel of our hospital (n = 93) and patients with various hematological disorders (n = 112). Our findings unveiled a robust positive correlation between serum hepcidin-25 and ferritin, as well as C-reactive protein levels, in both volunteers and patients. Among the patients with hematological disorders, there was a noteworthy negative correlation between hepcidin-25 levels and hemoglobin concentrations, as well as reticulocyte counts. Interestingly, the hepcidin-25/ferritin ratio was remarkably low in patients with hemolytic anemia and myelodysplastic syndromes with ring sideroblasts. Our findings suggest that quantifying serum hepcidin-25 and the hepcidin-25/ferritin ratio using this method may be valuable for screening of hematopoietic diseases and other iron metabolism disorders.