The study investigated miRNA-210 as a potential biomarker to distinguish iron deficiency anemia (IDA) from functional iron deficiency (FID) in 50 hemodialysis patients who were divided into control, IDA, and FID groups according to hemoglobin (Hb), ferritin, and transferrin saturation (TSAT) levels. Plasma miRNA-210 levels were significantly higher in the IDA group compared to the control (p = 0.0010) and the FID group (p = 0.0007). A significant negative correlation was observed between miRNA-210 and Hb (ρ = −0.363, p = 0.0155). ROC analysis showed a moderate diagnostic ability of miRNA-210 in differentiating IDA (AUC = 0.711, p = 0.0186), comparable to ZnPP and better than ferritin and TSAT. miRNA-210 may serve as a supportive biomarker reflecting the interaction between hypoxia and iron metabolism. Limitations include small sample size, single-center cross-sectional design, absence of a healthy control group, and lack of functional validation.